Michael Harding

Ok everyone. I got my light module working. Key on everything worked perfectly. Plenty of power to the module. Started car and all he'll broke loose again. This tells me there is a short somewhere other than the module. Any ideas on where to start would rock

Michael Harding

And this little diode got hot. I mean lava rock hot. I'm sure that's abnormal yes?

sofakingdom

iTrader: (1)

Where in the car was this "light module"?

That doesn't look like a diode; looks more like a resistor. Yes it's abnormal for such a part to get hot.

Scorpner

iTrader: (4)

If you run a new module in-line with a hard short you will ruin the new module as well. You need to find the short using a meter on beeper mode with the car battery disconnected.

Michael Harding

Module behind hush panel on passenger side. I know I probably sound like a moron but I have no idea how to work a multimeter. Have one but don't have much electrical skill. Cept for radios I'm pretty much clueless. 84 berlinetta btw.

Scorpner

iTrader: (4)

Oh, ok. You're the guy with the yellow Berlinetta. I've explained this a few times on here already. I don't have a lot of time but I'll write something up quick, but you can also search google and youtube to learn how to find hard shorts in most any circuit.

A circuit from the fuse (Ie. 12v) to ground always has a certain amount of resistance (multiple components, doing different tasks that take up energy), however if the circuit is shorted, then current flows as if there were no resistance. When current increases, the friction heats up everything in it's way, which is why your components are heating up more than they should. (If it helps: You can think of current as being analogous to the speed of water flow, and resistance as something that slows the water down. If most of the resistance is in one spot then it will heat up and burn out, in most circuits the friction is spread out along the path)

A meter in beeper mode tells you when you have continuity from one point to another. When you connect one lead to ground, and the other to a test point, you are searching for places that have little to no resistance. (The beeper mode is easier than looking at a numerical value on the display of the meter.)

The car battery must be disconnected since the meter puts out a low voltage of its own. You would then have the connector to the module to evaluate. One or more pins would be ground (usually black wire) and they should beep, the other pins should have various amounts of resistance and not beep at all. What you can do is look at the circuit board you have, and notice which traces (copper paths) are the widest. The widest are usually the ground circuit, which is typically designed to carry more current. If you see on the board where those traces match up to the connector and the wire on the connector is also black then it is most likely the ground circuit. (Also, as a note your entire chassis (metal body of the car) is also your ground). Sometimes GM uses similar colors for certain wires/circuits so you would assume those to not be of low enough resistance to set off the meter. If you do find a pin on the connector that appears to be shorted, make sure the leads are hooked up solid and try either; moving the wiring/harness around, or look for places where the harness or wiring are pinched or worn through and contacting the body. Speaking of this, it's important that you do not disturb the wiring before using the meter in the off chance there is a contact short that might go away before you get the chance to find it. (Ie. This would be say a bare wire that had worn through and is just laying against the body/metal.

Another thing you could try if you know someone that has access to the same circuit is to have them measure the resistance of each pin on the connector to see if there is a large difference between cars. There will always be some variance, but with something heating up that much it should be a substantial difference.

There is also the possibility that the module you have was in a different car with a shorted circuit. As I mentioned in the other thread, anything you get a hold of should be considered a core and (I'll add) should not be trusted as safe to just plug in and use. One way of finding out is metering the resistance between different points on a known good board and your new one. -If you didn't catch that, this is different because you're comparing/measuring board to board not chassis wiring to chassis wiring (between cars).

The basic idea in any of this is to understand that current is flowing from one point to another, and with that looking for a path that was compromised. There's a lot more out there if you search, and probably better explained that should help you learn how to do this.
-I wish I had more time to explain more clearly, but I hope that helps.

sofakingdom

iTrader: (1)

Problem with trying to troubleshoot this situation that way is, you can determine that the PCB trace "downstream" of that resistor, has a short; but then, if there's multiple components being fed power (or whatever) along that trace, won't tell you which one.

That's the ECM. That's what it looked like to me, and why I asked what I did. It's the "brain" that runs the engine. Has little to do with "light". The fact that you don't even know what it is tells us the level we have to start out working on this at. No disrespect to you, not everybody is an electronic design engineer like I am and I get that, just, seems like we gotta start at the very basics.

A little history here would be helpful. Tell us more about "got working" (they usually work fine, until they break, at which point they don't work so good any more); what you did that "got it working"; what the car was doing that made you think it was bad at the beginning of all this; whether it actually WAS bad, or whether instead you did something else (such as unplugged something under the hood) that made it appear to work; what you're talking about, about "plenty of power"; what "all hell broke loose" means; and so forth. We can't help unless we know what's REALLY going on.

OrangeBird

iTrader: (1)

Hey Sofa ,

Are you sure the circuit board the guy is holding is his ECM ? He says it's a Berlinetta and I know the Berlinetta does have a light module , and the circuit board he's holding don't look like the inside of the ECM I was looking inside of recently which is why I'm asking ?

To the OP , take clear pictures of that entire board , and of exactly where in the car you took it out of . Also , what type of enclosure was that board in , was it in the silver box visable in your photo or was it in a different enclosure ?

PS , when asking for help , it pays to FILL OUT YOUR DAMN PROFILE !!!! so folks know what model thirdgen your asking for help from . Berlinettas do have a lighting module that no other third gen has , and I hope "John in RI" stops by cause he's the Berlinetta expert here .

Oh , and you may want to ask a mod to take this out of the carb section and put it in the electronics section where it belongs (can't see this being a fuel system issue from here !)

Scorpner

iTrader: (4)

Sofa, I know some of the history of this car from an earlier thread. I agree on the circuit board. What I was trying to do is relay the general idea in such a way that it could include other electronics down the line. The idea is first to check at the connector outwards to the harness while it's unplugged to make sure the circuit board isn't being pulled down by something like a pinched wire to the body, or another module etc.
Then if that's ok, then compare the circuit board to a known good one if possible. Otherwise it's going to be more involved as you are saying.

Thinking now, that module he is looking at may actually be an early version of the body control module (Berlinettas have auto shut off headlights and delayed radio/interior lights (probably on a 555 timer)).
What was posted in the earlier thread was issues with the headlight control pod on the LH side of the steering wheel. What he has now is on the passenger side.

...So yes, I am also waiting for John to chime in.

sofakingdom

iTrader: (1)

No actually, I'm not sure what it is at all. I shouldn't have jumped to that conclusion. Could be the dash controller or body module. I don't really know the ins & outs of all the Berlinetta-specific parts.

Probably doesn't make that much difference in the long run though; troubleshooting a shorted part works the same regardless. But it might just be harder to get replacement parts once the fault is found, if it's some part unique to Berlinetta.

Just the same, a better description of what it is and what's going on, would sure help point the process in the right direction.

Michael Harding

OK I'll explain this a bit better. I bought the car (84 berlinetta) the guy told me the headlight relay was bad. At the time had no idea about that light module or I wouldn't have bought it. Part is obsolete now cept for used that are also not the easiest to find. Now for the fun stuff. When I turn on the key the hazards start flashing and won't stop. Inside courtesy lights stay on which drains the battery. No headlights unless I hold in the brights button. Digital speedo, tach, odometer , voltage meter, oil pressure, temp guage all work. No turn signals or gauge cluster illumination. Now then I unplugged the light module. Plugged back in and it worked like a champ. Turned key to on position and everything worked perfect. Now I turned it a little further to the start posistion lol. Heard a click on the light module and it went back to not working. The board I'm holding has all the headlight flasher ect. Relays on it. Which is to my knowledge the light module. When I said it was getting plenty of power to it I meant with the key on. 12 volts of power with key on and while cranking if I'm not mistaken so what I'm confused about is why it would malfunction only when I start the car? And sorry bout not knowing electrical. Not to much call for any of that where I spent my college years lol. Sorry I don't know how I can explain the problem any clearer. When I start the car it malfunctions. I unplug module and plug back in. Key on works fine. Crank engine and it malfunctions. Now all electrical doesn't confuse me I can wire up a car with the best of them and wire in relay and fuse boxes. The confusion is with the circuit boards (aka worst thing to ever happen to a car). I would rather just send the module to the bottom of the ocean where it belongs and wire in a nice relay bank. But would like to keep the digital gauges and such and I'm pretty sure without the circuit board I can't keep those.

John in RI

iTrader: (167)

Not even close. However; you are right in one at least one way,.... but it applies to YOU,

The fact that you don't even know what it is tells us the level we have to start out working on this at.


Mike knows what he has and several members that DO actually know what they are talking about have written to him online and I have written to him privately thru E-Mail several times to help him with these problems. He's already been offered the opportunity to acquire the parts needed to resolve his lighting problems - but still feels the need to try and 'fix' his original Light Module. All we can do now is sit back and watch as Mike takes on the repairs by himself.

NO ONE, Let me repeat: NO ONE knows how to repair a failed Light Module, so Mike is on his own & If Mike can figure it, we will all benefit. The best place for him to start - IMO - is to learn how to use a Multi-meter. Not that learning how to use it will help with this problem in any way,..... but at least he can probe the wires and see what we already know - the Light Module needs to be replaced.

John in RI

iTrader: (167)

If you disconnect the light module and turn the key to run,..... The dash should still works normally. This is truer until the headlights are turned on; Without a Light Module connected the Digital sections of the dash cluster will go dark.

The Light Module is only related to the cluster in 1 way,..... it supplied DIM voltage to the cluster when the headlights are turned on. If you use some other method to supply the cluster with a DIM circuit voltage when the headlights are on,.... the dash cluster will work just as it always did.

Michael Harding

True and as soon as I can I'm going to get a module. From present company of course seeing as you're the only one that has any lol. I just don't see how these can't be repaired. I mean a circuit board is a circuit board yes? People repair circuit boards all the time. Just wanted to pinpoint the problem for future reference because it's just going to go out again and again so being prepared isn't a bad thing. Yea it's toast but i figure why not try to see why it became "toasty" in the first place. Don't think I'm not taking your advice John I am. You're the berlinetta guy and uu know your $@#%. I'm only curious as to how and why. Knowledge begins with curiosity.

John in RI

iTrader: (167)

I truly feel your pain and have lived with it for 25 or so years as a Berlinetta owner because I have never found anyone with the skills needed to repair dead units. ( Same is true for the myth that the factory speedo can be modified to show speed over 85MPH !! ) I might know my way around these things, but will never call myself a "Pro". In the last few weeks I have been in contact with an actual electronics professional and I'm hoping that I can work with him in the future in an attempt to get him to look into repairing these things. ( not the first "professional" I've tried ! )

For the record; As I explained to you earlier; The Light Modules I've got right now do not have a working DIM circuit. I have figured out how to by-pass that feature and the by-pass must be used with the Light Module that I offered you.

Michael Harding

OK correct me if I'm wrong but the dim circuit just tells the dash illumination to dim when lights r on is that right?

John in RI

iTrader: (167)

Yes,.... BUT;

When the digital cluster accepts the lights on signal it switches from allowing the cluster full illumination,... to the viable voltage supplied from the Light Module. ( This happens INSIDE the cluster ). When there is no DIM signal,... there is NO digital display readout.

Symptom of bad DIM circuit = Everything on the Digital Speedometer works fine during day-time driving, until the headlights (or park lights ) are turned on. When the exterior lights are active, the digital sections of the cluster go dark,............ as well as no I/P, console bezel, Radio, or Pod lighting.

Michael Harding

So.....I'll be able to SEE where I'm going just not how fast I'm gettin there. Lol ah the old give and take. Gotta love it lol

John in RI

iTrader: (167)

The DIM bypass is very simple, very quick to install and it's very easy to acquire the parts. NO NEED to become a 'electronic design engineer' ; This is HOT ROD STUFF !!! Splice 3 wires and install a remote Dimmer; DONE.


Then you can see where - and how fast - you are going !

Michael Harding

Lmao oh good God I'm a retard. I see precisely what you are talking about now. And see it only took u explaining it 14 thousand times for me to click lol

Scorpner

iTrader: (4)

I'm sure they can, but IMO, there are quite a few factors that keep this from happening.

• The existence of propitiatory chips that GM typically uses (chip function and sometimes sourcing them). Not typically unique but a pain none the less.
• Time/interest to reverse engineer the circuit/s.
• Inherent faults in design
• Cost to have someone else do it.
• Labor intensive, age related repairs.
• Competition of preexisting repair shops of variable quality/knowledge.
• Viable alternatives. (Replace dash, hoard modules, after-market gauges, Carputer/touchscreen/tablet options).

The fact that Berlinettas are rare presents a unique situation. If you were considering a TTA or 1LE, everyone would want one and pay a good price for the car, unique parts, and repairs (that's why it's easier to find places that fix them). The problem that I have run into is that Berlinetta are not as widely desirable, but at the same time people that possess the parts want a premium price. This generally holds true regardless of the condition, and many selling the parts have no way of testing them, especially long enough for typical problems to present themselves.

Another unique situation is the short duration of manufacture, and the low probability of substantial revisions. What this means is that the first run of any new technology inherently brings forth issues that are typically resolved when the next batch of parts are produced. It's not feasible to fix problems right away unless there is a catastrophic failure and/or recall. So these units are probably at a first run, market test level.

What does this mean for us? Well, whatever design flaws these parts have, are most likely something that cannot be easily remedied, especially at a reasonable cost. There would be no examples of revisions so that we could benefit from GMs engineering resources, and possible fixes for the earlier examples. The buttons for example wear out, but those are easily fixed. If the light pod and/or module here has an inherent design flaw (to the point to where it is a common issue) ...you may be able to repair them, but they may eventually fail again. Most of the time something like that is guaranteed to fail over time, and if not repaired correctly, cause further damage. (Sometimes evaluation of an improvement on this level involves heat/cold cycles and long duration testing with instrumentation/recording to evaluate variances and extremes. Ie. GM level commitment) Anyway, if it was a problem that a GM dealership encountered back then, the fix would alternatively be to swap out another module from the leftovers, or replace with a used one.

FWIW, I've reversed engineered and built circuits back when I graduated just to see if I could do it but I personally lose interest with the propitiatory aspect of it. I even repaired a GM radio for fun, but sourcing the correct parts at the time (before internet) took more effort than it was worth vs. buying an after market stereo. If the moon and stars aligned to where I had the time and inclination I'm pretty sure I (or anyone familiar with component level repair of GM electronics from this era) could figure it out.
I personally do not have the circuit boards mentioned that are known to be faulty, or the time to play around with them. I wouldn't even want to introduce components into a good vehicle and might even consider building a test fixture/harness if I were to evaluate something like this on a regular basis.




Here's how I look at it. There were approximately 50,000 Berlinettas built. Many were crushed, others parted out and the parts hoarded. Most probably had substantial mileage, and all are the same age. One more factor not brought up yet is that most of these will also present problems with aged electrolytic capacitors and cold solder joints. That can be easily repaired (but labor intensive), however remember that most units that you would buy today would be at a premium price. Add to the fact that these repairs may need to be done before you could even troubleshoot and/or repair any major problems.

Ok, so 50,000 built minus those no longer on the road. Take away the ones with the dash swaps, gauge swaps, piles of pods, and carputer conversions. Also take away the Berlinettas that have been preserved (since most of the problems appear to be age(usage, Ie. Heat cycle/vibration etc.) and wear specific).

Now there are “X” number that will need replacements/repairs. You may have ten times that many parts out there and a certain number may even work as is ...in various degrees. (Most will just put up with minor problems, especially on a weekend cruiser.) My thought is that the majority of these Berlinettas will not be original, not low mileage, and therefore not be of enough value to support repairing these on a large scale. Ie. (Alternatively on the consumer side: two pods, a module, display and radio. Who can afford that? In comes pressure to do more for less.) Bring in the established businesses that could easily eat up any competition when the volume becomes sufficient, you then have little motivation to pursue that particular market. Add to that any inherit problems that increase the cost of repeat returns, time with upset customers, damage to reputation, user error, and the like. Then also add to that the amount of time/labor re-flowing solder and swapping massive amounts of capacitors, trouble shooting and putting up with brittle plastic that crumbles when you disassemble the pods.

Same goes for the radios. It's often too time consuming to repair vs. replacing with newer technology. Same also for the mechanical dimming mirrors that I have played around with. I would never repair those on a regular basis due to the common issues inherent in the design. Those were revised but replaced with non-moving parts and became much more dependable.

Anyway, sorry about the length. If I had the time I might check it out for fun. But there are more fun alternatives for me to consider. It does bother me because I am curious and it would be great to help and/or make a little on the side. It's still much easier and possibly cost effective (if you look hard enough) to gather extra pods for now until you find one that works.
Either unit of this light module circuit most likely has a specific part failing over time. That one part could be taking out other parts down the line and possibly taking out the other circuit board. The fix is to find out what is happening and trying to find an upgrade to eliminate the problem, then replace the other components.

John, if it hasn't been done already, I see what looks like a transistor on the side of that unit that might benefit from fresh thermo grease.

OrangeBird

iTrader: (1)

I wholeheartedly agree with Scorpner , that board should be easily repairable by any electronic technician worth his pay . The only two possible components I see that might be difficult to source would of course be that 28 pin IC and the crystal (depending on it's frequency) . All the other transistors , diodes , resistors , capacitors , and relays , the things that cause the greater majority of problems , are available in any good electronic supply warehouse store .

PS , Scorpner is also 100% right about the importance of the thermal compound (heat sink paste) . When it looks dried out and chunky like that it's lost some of it's ability to transfer heat and should be cleaned & reapplied with fresh stuff ...

Michael Harding

Yall had me at turbo t/a lol. Absolutely love firebirds. Had a 95 firehawk, a 79 trans am, currently have a 71. Well the chassis anyways. Minus engine trans and rearend. Thought I would try my hand with a berlinetta. Now I'm wishing I had cut that hand off lol. But no I finally clicked at what was being explained to me. Guess I was over thinking it. I talked to a guy I used to work with at benchmark electronics. They build circuit boards and such. He told me they could easily make one but they only build in bulk. Sucks but it can be done. Maybe a little bribery would help lmao.

John in RI

iTrader: (167)

Scorpner; I almost certain that component is the reason for the - all to common - DIM circuit failure. There should be a very slim plastic washer/insulator used in that spot between the "transistor" and the metal body of the assembly. ( where it's bolted thru the side of the circuit board ) MANY of the Light Modules I have gotten over the years are missing that insulator; almost certainly because un-knowing owners take this thing apart to 'look around' and loose it or simply don't re-install it.

Orange, your sooooooo right ! It's eighties tech for Pete's sake, how hard can it really be to figure out ! As Mike pointed out,... qualified techs/companies want bulk work and don't even want to talk about figuring out a 30 year old car part for 1 customer. Maybe someday someone with the right skills will become a Berlinetta owner so it becomes "important" !!

Scorpner

iTrader: (4)

You've found a plastic piece there? It looks to me like a high current transistor, and if it is, you would actually want the metal to metal contact. The thermo grease is there to help conduct heat more efficiently.

I'm pretty sure that I've seen some GM radios use the case as a heat sink in the same way.

DonW

I just read this thread and now my brain hurts. Stupid light module!

Caudheezy84

Hey John from Ri. Check this out.

Me and my buddy brought the entire interior and both computers back to life. Only had to use one aftermarket switch. Solved the dim/light issue.

Anyway.... one problem left the signals/hazards turn on with engine on. But work fine with engine off.

I think installing a 12 volt resistor between the alternator and the light module will fix it.

If it doesn't, I'm installing an aftermarket signal kit with it's own relays and flashers. But using the factory pods for control.

What's your opinion?

John in RI

iTrader: (167)

One of the failings of these LIGHT MODULES is that they seem to work fine when the car is off,... but as soon as the car is started - weird things happen. In some cases the Headlights will turn on, sometimes the High Beams turn on the hazards go crazy, and nothing will shut off unless the battery is disconnected or the proper fuse is pulled.

It's my belief that the Light Modules internal circuit breaker is responsible for this fault. The Light Module will work fine with around 12 volts - but as soon as the Alternator starts to work and more then more than 12 ( or so ) volts is pushed into the Light Module - it freaks out because of the bad 'circuit breaker'.


This Power Circuit begins @ the Starter, passes thru a fusible link, then to C100 'G5' ( Power distribution circuit ) then is factory spliced in the dash harness and leads to the Light Module Connector C2 PIN 'F', ( heavy gauge, RED wire ).

I'm GUESSING that some type of a voltage regulator or circuit breaker placed in-line on that RED wire just before the Light Module *MIGHT* resolve your problem.

naf

iTrader: (7)

anyone yet consider replacing the functions of the light control module with a later model BCM?

I intend to put some effort into this over the next few months. would appreciate being able to piggyback on another's work...I recall seeing a 4th gen BCM used to control remote functions somewhere.

John in RI

iTrader: (167)

Never tried it myself. I think that most BCMs are VIN coded,... but maybe there are early types that don't require a VIN on the DATA circuit ??