CanadianBeast

Hi I just noticed that my tach drops about 300-500 rpm with every flash of the turn signal, both left and right. Anyone see this before? Any ideas?

My car is an 89 iroc L98 automatic

Thanks

89Irocz23

I want to know what that is too cause my car does that too. I believe its low voltage cause i cars use so much power. But mine does that too. the volt guage and tach moves the same when my blinker is on.

CanadianBeast

I also just noticed that it does it even worse if the key is set to on. When it's on but not started all of my gauges jump with the turn signal, except the speedo of course.

camarokev400

AHHHH finally someone is having the same trouble as i am.... this has been driving me nuts for like 4 months now i have no idea what causes this but it is so annoying. My tach only jumps with the right signal but it jumps like 2000 rpms. Camaro's electrical stuff sucks!!!!!!!!

irocz8292

It sounds like a voltage problem, but try the grounds first. Make sure all of the groudns are good. Mayeb even run some new ground wires.
And yes, our car's wiring sucks.

Danno

It is perfectly NORMAL for a TG with a 105 amp alternator to do this especially with the AC and cooling fans running. This will almost always occur at idle. During this time electrical demands on the electrical system exceed what the alternator is putting out. As I stated on other posts, a higher output alternator will have less output at idle and more when over about 1000-1500 RPM's. You can overcome this with a smaller alternator pulley, a lower output alternator or simply live with it. Some people claim they can overcome this with a larger capacity battery but don't be mislead. I has to do with voltage drop because the battery is being drained and alt output is low. Unless you sit in traffic for 8 hours it is nothing to worry about. When you factor in the AC compressor clutch, the cooling fans, blower motor and any accessories under that condition you have possible a 35-40 amp load on the battery. These batteries are generally rated for 60-75 Amp-hours so you see there is quite a draw and voltage drop is common even with everything being tight. A few minutes of cruising will bring it up fast. Periodic trickle charging the battery will extend it's life and help the alternator to last longer. This is not just a quirk with the TG's, many cars will exibit a 2-4 volt drop with heavy electrical demands. This is why several makers are going to move up to 48 volt systems in the future.

camarokev400

no this isnt being caused by the alternator it is def a bad ground somehere or something, but it isnt voltage... the engine speed does not change the tach just jumps all over the place no matter if the ac is on or not

Danno

OK, I will explain this one more time. I did not say it was a fault with the alternator. It is simply the fact that the alternator does NOT charge at idle. No if's and's or but's, it won't. Any modern car with a heavy electrical load cannot and will not charge the battery at low RPM. It is NOT a ground, and if you think it is you will spend the rest of your natural life trying to find it. Your battery has the capacity to give off 60-75 amps for one hour. If the current drain is half of the capacity of the battery then the voltage will drop based on the condition of the battery and state of charge. Even assuming you have a batt in a full state of charge, if you draw half of it's capacity for even a short period of time it will develop a voltage drop. You can look all year for a bad ground, and guess what? Ain't one. You want another enlightment. Get an AC voltmeter and check your voltage at any receptacle in your home. Monitor it for a 24 hour period. If you have central air when that compressor kicks you will see your AC drop 20 volts or more depending on condition of the wiring. A fact that most experts cannot accept is that your alternator only responds to voltage drop. It has NO idea of the state of charge of the battery. Don't believe me, contact a battery manufacturer. What you percieve as a problem is not a problem at all. I do not mean to sound rude or like a know it all, but this is what I have done for a living for the last 30 years. In many cases in a modern car the load on the battery far exceeds the alts. output at the time. It is not a problem, it is a function of the way the charging system works. And of course it is DEFINITELY voltage that causes these flukes. Whether it is AC compressor or not does not matter. You must calculate load current and then have a reference for battery capacity to determine whether or not you can improve what you see. You will not improve what the engineers designed. I have worked on I can't recall how many TG's. Every one is the same. The only TG I ever found that did not respond to load changes was one that was retrofitted to accept an old 10si 63 amp Delcotron alt. That bastard put out close to 25 amps at an idle of 500 RPM's.

camarokev400

Allright then what would cause all this then: when i turn on my headlights, my right turn signal stays on, my tach jumps to 7 grand and will move to my dash dimmer switch i can move my tach from 0-7000 rpms, i loose oil pressure, volts... and when i turn on my signal switch the tach jumps and it is not the headlight/dimmer switch... however when it is dusk out and i dont need to see my dash lights i dim them down all the way and everything comes back, but as soon as i turn them back on i loose half the guage lights and gauges....certainly sounds like a ground to me... i understand what you are saying about the voltage too but i dont think my problem is related to it... i didnt tell you all my problems before so i understand what your thinking. The tach actually bounces off 0 and goes all the way to 7000 i dont think your picturing this ill take a video for you and post it, its a very wierd problem

Danno

That is pretty radical. You are right, that is not the normal (I call it the twitch) problem we see. I would definitely agree that you have a loose or corroded ground somewhere. Ok, lets look at the turn signal problem. You say with lights on the turn signal stays on. Do you mean it does not blink. The turn signal stem won't turn them off? I suspect you mean they stop blinking or at least I hope. Two things could cause that. One is excessive voltage drop or a high resistance in a common ground to all these circiuts. To start you need a cheap voltmeter. Duplicate the problem and probe the terminals right at the battery. With lights on and whatever else you need to generate the problem see what the voltage drop is. With a good battery and alternator it should not go much below 12.6-13 volts. If it OK there, then go to the fuse panel and check to see how many volts you have at the fuse feeding the turn signals. On the cavity fuses you can measure voltage without pulling the fuse, they have a little open spot on either side to measure with a sharp probe. The voltage should be within about a volt of what is at the battery. You can use the car frame for the ground of the meter for this test, I clip my ground to the door light switch. If you see a large drop then you work your way back. Common area for problems is the junction at the starter solenoid. Generally removing the connectors and giving them a cleaning is a good idea. Sometimes a firewall grommet deteriorates and water get's behind the fuse panel corroding it. At the battery does the voltage go up to at least 14 volts when you rev the engine? Mounting bolts for the alt tight? It get's it's ground through the mounting frame. It can be a little painstaking but if you give me all the info you can I'll walk you through it.

camarokev400

haha yeah its not just a twitch... and the turn signal indicator will stay like it does when one of your turn signal bulbs burns out but the light still works outside... the indicator just stays lit up in side it does not blink just stays lit up...

racerx004

I have an 84 Z-28 that has been sitting for the past 5 years.
I have fired it up once or twice a year to keep it going, now that I am getting back into it I noticed this same problem.
Here are the exact details.
I don't have a/c.
With the car started everything is fine, but as soon as the you turn on the headlights this happens,
voltmeter drops to zero,
oil gauge drops to zero,
tach either jumps to 7000 or go's to zero,
right directional light comes on and stays on on dashboard.
Also my fuel gauge is pegged at above full although this could be seperate because it was working then went haywire.
I noticed that even though the right directional light is lit on the dashboard the lights outside all work fine. All directionals, brake lights, backup lights marker lights,plates etc all work fine.
When I use the flashers the directional lights on the dashboard allternate on and off, yet the lights outside flash normally.
Also the right directional light opperates with the dimmer switch along with the rest the lights on the gauge cluster.
Also a few of the bulbs around the Tach seem to be lighting VERY dimmely.
With the key in just the on position the same problem happens when the lights are turned on. The oil gauge drops below zero and the volt meter drops to nothing. The tack usually spikes to 7000 rpm even though the car is not running.
It seems like there is a power draw from somewhere, or a bad ground.
I have tried removing the gauges from the cluster, but the lights on the back of the cluster behind the tach still don't light up.
If I make any headway on this problem I will post it here.
Any help or suggestions from anyone would be greatly appreciated.

camarokev400

exactly the same problem as me, it sucks dosent it!!!!! i have tried everything... it has bugging the hell out of me for the past couple months.. started doing it every once in awhile and then go away but not it is every time i put my headlights on without dimming the dash lights. It is very annoying let me know if you figure anything out

racerx004

I believe the problem is isolated in the gauge cluster housing itself.
I have a digital dashpanel made by cyberdyne insturments.
To use it you remove all lights and gauges in the cluster and just use the plastic housing and the printed circuitboard with the panel.
When I removed all the lights except for the check engine, choke, directionals, brake, and seatbelt lights, the panel worked fine and the right hand dirctional light was VERY dimmely lit, but almost out. When I turned on the headlights, ad adjusted the dimmer the digital gauges were fine.
I think it is a short in the printed circuitboard or one of the light sockets may be bad. I talked to a freind wjo knows about this stuff and he also thinks the problem is in the printed board.
I needed a new speedo anyway so i'm just going to buy a gauge cluster on monday from the local junkyard.
If this resolves the problem I will let you know.
One note I tried removing the lights to see if this let the gauges work, but the gauges need the light sockets to run.Also when I removed the gauges the lights behind the tack didn't light and the directional was still on.

camarokev400

Yeah i have messed around with my cluster also... i only have a 85 mph speedo so i am thinking either custom dash or head to the local junkyard and see if i can find a cluster with 115 or 145. I would like to get white face ones to match all my other gauges:

racereddy20

Hey racerx004 and camarokev400, I have the same problem here. i believe that it is a bad ground or a loose ground wire. Sometimes when I hit a pot hole or a defect on street everything works till I hit another pot hole or bump on the street. i'm pretty good at figuring out electronics problems (at least on laptops and computers) and i think I can figure this one out too. I just havent had the chance to look at it. Racerx004 you described my problem down to the "T". I'll let you know when I figure it out. Also does anyone know where I can find the pig tail that plugs into the fan. I had to make one from scratch (mine was melted together when I bought the car). I broke mine up when I had to replace the fan motor. I made a harness but it just isnt stock. I like the stock look. I already checked the junk yards here and the've been picked clean.

racerx004

I finally got my gauges to work right again.
The probem was definitly in the printed circuitboard on the back of the cluster.
It must have either been a break in the copper, or a short in the board. I suppose a badly corroded light socket could make this happen also.
I picked up another gauge cluster from the local junkyard.
I took a battery with me just to make sure the cluster would work when I took it out. it did work in the junk car.
When I got home, I plugged it in to my dash.
Except for a few burnt out bulbs, everything is working normally.
I even replaced those burn't out bulbs and everything still works.
I hope this helps you guys.
If you need any help just let me know and I will try to help as much as possible.
Thanks to all those who helped me.

tpi_roc

racerx004 is correct, this problem is very likely in your printed circuit. If someone would like to flip over their cluster, take a picture of it semi-close and send it to me, I will circle the area it *likely* broke, I can also tell you a way to fix it.

racerx004

Hey TPI, befor I put the new cluster in, I took pics of the circuitboard with my digital cam.
Send me your e-mail address and i will send them too you.
My e-mail is racerx004@yahoo.com

tpi_roc

I emailed ya.

tpi_roc

racerx004 was nice enough to provide the following picture. I circled two spots. Point "A" Is where I found a break on mine. Its one of the narrowest spots on the printed circuit board and its the ground for every back light light, so as you can see if it breaks at point "A" everything on the right half of the cluster stops working (and sometimes the right blinker goes solid).


There's a little plastic "bump" below the copper right at point "A" that the bulb there uses to hold it in place, over time its very easy to wear through it. What I did was peeled back some of the excess copper in point "B" (for things like the choke light, something TPI guys dont have) and I pressed it in place, put some scotch tape over it, then put the bulb back in which held everything in that spot (make sure some copper is exposed for that bult to contact)

Thanks racerx004, and best of luck to everyone else, I hope this proves easy to find/fix.

racereddy20

can point a be fixed? What I mean is can you solder in a lead to repair that spot? You guys have my problem described down to the t.

Danno

The PC foil can be repaired if you are careful. A jumper wire can be soldered to replace the broken foil. There are comercially made pc repair products on the market to basically "paint" a new fiol in place. If you have not worked with pc type boards I would take it to an electronic repair shop. For a couple of bucks you can probably get the guy to do a nice job since in thier line of work they do it all the time. Even though this is not really a printed board(it's called a flex circuit) you can make a mess out of it if you are not familiar with delicate work.

racereddy20

i work on laptop electronics all the time. I've just never encountered pc foil. I've soldered chips onto motherboards (0.5mm thick). As a matter of fact I had to resolder a memory tester last week. Some one forced a connector in backwards and literally broke off two pins. So I replace the pins rather than the whole connector itself. I've really worked with small electronic components. I have soldered on leads to replace a broken trace or to update an older prototype board too. So my answer is yes? If so thanks, now I just have to rip apart the dash.

camarokev400

thanks for the info guys... i finally found a 145 mph cluster that is on its way hopefully it will be here this week. I hope this will fix my problem

camarokev400

Everything is perfect now!!!! I just put the new 145 mph cluster in with my white face gauges and everything is working perfectly, you people know your sh/t

KlayBuRn

Sounded like a good excuse to get a 145MPH Speedo

camarokev400

HEHE exactly took awhile to find one but i got the whole cluster for 100 bucks

KlayBuRn

How did you adjust the mileage cluster wise? In my old RS, i was going to put a new cluster in it, and use a little motor thing to adjust to the miles i actually had...

camarokev400

I didnt adjust my mileage im not too worried about it i plan on keeping this car the rest of my life so its not a big deal for me, since all of the stuff is either new or has been replaced at one point in time

brodyscamaro

Heres my post about this problem. I guess I am getting a 145 speedo or autometers. THANKS!