Ozz1967

iTrader: (4)

Hey guys,

84 T/A, single electric fan, CC Qjet. L69 set up.

So, since the weather turned cold, I've had to let the car idle at high idle (Currently set to 2200 RPM) to let the car warm up. I've been smelling a burning rubber/plastic smell. Couldn't figure it out until I realized my fan didn't turn on one day in traffic.

Sure enough, the fan switch plastic connector is all melted which caused the connector to fall off of it (Found this out sitting in traffic when the fan didn't turn on). With gloves on, I manged to get it suedo-connected to run in order to get me home (Finishing a 500 mile trip). The fan did work for the rest of the trip until the wire came back off the connector.


To this point I"m running a Jet Fan switch, On 195, off 185. I had a hypertech switch sitting in the garage (I accidentally bought it last year when thinking it was causing fan problems that turned out to be relay problems) that I swapped in.

The fan still doesn't turn on.

Any thoughts on where to look what to check? The threads are the same, however the hypertech has what looks like a tang, or metal piece sticking out the bottom about an inch farther than the Jet switch. When I tightened it down, it seated ok, I got the plug on with no problems and it's spliced in properly. This is a "one wire" type plug, I know some of the later ones had dual wires. So...what else could it be?

If i have to order anything, being in England, it will take 7-10 days to get here. Relay (Relay was replaced last fall)? Fuse (I didn't see a fuse that said "fan"), fan motor?

What's the easiest way to bypass the switch to see if it's the motor? Just ground out the wire when the engine temp gets up? Touch it to the negative battery terminal or the back of the AC compressor where there is a good ground?

Is it possible, that the "tang" that sticks out form the switch is touching the far side of the water jacket, causing it to act like a heat sink? King of grasping at straws because well....I didn't expect this to happen. All else fails, I just order a new Jet Switch and go with it and hope that's it.

I also posted this in the cooling section but figured this gets more exposure. I apologize if I wasn't supposed to do that.

Any help is appreciated.

naf

iTrader: (7)

Ground the switch lead and the fan should come on with the engine in 'run'.

The tang 'may' be a ground lead for the switch? Easy enough to check.

naf

iTrader: (7)

FYI

The factory switch has a thermal switch in it that closes a circuit between the switch lead and the body of the switch, effectively grounding the lead to the engine block (or cylinder head). Grounding that lead on the relay will turn on the fan (with engine in 'run').

Some aftermarket switches have two leads. The thermal switch in them closes a circuit between the two leads. If one of the leads is connected to ground, the relay lead is grounded, like our factory system wants.

Need any help just ask.

Ozz1967

iTrader: (4)

So, if I'm following, if I simply take the lead off the switch, ground it to a chassis ground with the ignition in "Run", the fan should come on?

Mine is a "one wire" set up, or one lead as it were. Only one pin on the connector and fan switch itself. Same as it came factory. Even though I have modded some things, I do like to try and keep the factory operation where possible. Hence the factory fan set up as opposed to running an aftermarket fan controller.

Ozz1967

iTrader: (4)

The "Tang" side is in the motor, I didn't know what else to call it. I believe it's actually the sensor part of the switch. The outside of the switch has a black mushroom-looking connector with a single female lead in the center that the connector plugs into.

The Jet switch had threads, then ended with a smooth end on the "engine" side. THe hypertech switch has the smooth side, plus a 1" long cylinder that goes farther into the motor. It's that cylinder I called the "Tang". I didn't know what else to call it. Sorry.

Ozz1967

iTrader: (4)

Ok, small update.

I turned on my "AC" today while the car was idling, and the fan did not come on.

vetteoz

iTrader: (13)

Did fan run when you did that?
Assumes of course the relay is good , that you have power to the relay , the fan fuse is good and wiring in between is fine

Possibly bad A/c pressure switch

Ozz1967

iTrader: (4)

When I first noted the issue in traffic, I got the fan working by getting the connector to hang back on the melted plug. So...as of last Friday it was working. As the majority of my trip to and from work is highway, I don't need the fan that much if at all if the traffic runs well. So I just pulled the wire back and held it out of the way from hanging down onto the headers.

Saturday was the first day I installed the new switch and noticed the fan didn't come on when the engine got up to "fan temp" of 205* (New hypertech is 205 on, 190 off.

I haven't grounded the new connector yet, didn't have a chance last night and went to work today. I'll try and check it before I go home. Also, before now, this fan came on with the AC all the time, so I know that unless it "just went bad", it should be good.

Which fuse controls the fan? I looked at my fuses and didn't see one with "fan" labeled on it.

naf

iTrader: (7)

If it's not coming on with the AC, it's probably not a fan switch issue. Hard to relate the issues, but 'perhaps' constant intermittent operation of the failing switch damaged the fan motor or relay.

The fan doesn't have a fuse. It gets power from a wire connected directly to the battery terminal on the starter. This cable has a fusible link (fat/plastic part) that will blow under over amp.

Pull the relay connector loose and verify 12V constant on one of the fat leads. This will be the lead to the starter, the other fat one goes to the motor.

Check one of the smaller leads for 12V with ignition in 'run' only. The other lead goes to the fan switch (and AC control head or pressure switch). If all these check out good and you've verified continuity between the relay connector's end of the switch lead and the switch, you should be able to ground the switch lead and run the fan (with ignition in 'run').

Ozz1967

iTrader: (4)

The fan relay should be the same as the one right next to it right? Could I just swap relays?

Ozz1967

iTrader: (4)

Also, I didn't consider the intermittant issue possibly killing the relay or motor. I do have a dual fan setup for a future swap, are the motors the same? I could swap one if they are.

naf

iTrader: (7)

Motors are the same, relays may not be.

Did you get the newer style relays with the dual fan setup?

Ozz1967

iTrader: (4)

No, I don't have the new style relays yet. This was going to be a summer project and I was deciding if I should run both fans on relays, or just one fan off my existing relay and use an aftermarket controller for the second.

Alternately, I was loking at maybe using my existing relay and somehow hook up my existingsingle to run both fans as my existing single fan currently runs (On/off with fan switch, On with AC on etc.

I don't have a new relay to try, but I do have those other motors I could swap in.

Bad week for this to start, huge inspection coming up and working lots of overtime to get ready for it. No time to work on the car unless I do it after 9pm in the dark. hehe

naf

iTrader: (7)

Can't run both fans off the same relay, too much amps. You'll want to separate the systems anyway for redundancy, in case one goes down.

Ozz1967

iTrader: (4)

Hmm.

My long term goal was to go Fuel injected, TPI set up or the like, maybe a miniram, swapping out my CC Qjet. I would get a complete TPI harness to do this. I'm sort of buying the parts piece-meal as I go, the dual fans were step one. Followed by the harness, then a miniram and all the sensors. Probably a couple of year project as I'm looking at changing jobs here in the next two years so money is going to be short.

So, back to the Fan.

1. Ground the Connector from the switch with ignition in "on". Any chassis ground should work. If that doesn't do anything....

2. Check to see if the fan works. Disconnect fan from harness, positive lead to positive terminal on battery, negative to negative terminal. This will tell me if the fan motor is good.

3. Check voltages on relay.

4. Swap/replace relay.

5. TBD...possibly any combination of the three items is bad from intermitant power on/off from a loose connection.


That's my short order of doing things. I really hate working at night, but...got to do what ya got to do.

naf

iTrader: (7)

If grounding the relay doesn't turn on the fan, try connecting a spare fan motor to your fan connector. See if that spins. Just hold it steady as it may jump a bit when it starts.

Ozz1967

iTrader: (4)

actually, I'll try the fan first I think, not sure if I have enough play in the whole harness though. We'll see. Good idea though, thanks.

vetteoz

iTrader: (13)

Don't have a circuit diagram for your year but on the later years there is a fan fuse for the control side of the relay (not for the fan itself) that supplies key on power to make the relay operate
Quickest check is to disconnect the relay and jumper the two thick wires on the plug
If the fan runs you know the motor is OK and you have power to the fan through the fusible link so you are then looking at a relay control problem
That is; the relay itself, the power to the relay on control side, the temp switch or all the wiring in between
If the fan doesn't run and you have confirmed 12V available on the thick wire at the relay plug then motor is suspect so you need to do the motor test you outlined above
If you don't have 12V then the fusible link is suspect

Diagram below is from a '84 Vette with similar fan control setup to give you a idea

naf

iTrader: (7)

[QUOTE=vetteoz;5498816
Quickest check is to disconnect the relay and jumper the two thick wires on the plug[/QUOTE]

I hesitate to suggest this because if the motor is shorted to ground it could ignite some brief fireworks.

Ozz1967

iTrader: (4)

I FINALLY got the time to work on the car a little today which did produce some results...

1. Ground switch pigtail to chassis ground: No dice.
2. Take spare fan, plug it in, ground pig tail to chassis ground. No dice.
3. Removed single electric fan. Jury rig power leads to battery. Minor spark on battery as I touched the wire, but the fan spins. = Fan motor good.

This leaves me either the relay or whatever inline fuse there may be in the system. Still the potential for the switch to be bad also but as it was new-in-box when I installed it, I'm going to assume that's good. So, I'm ordering a new relay because that's cheaper and hoping the switch and wiring are both still good.

Naf, I'm going with your theory that the intermittant operation when I had it plugged up temporarily to keep it running on the highway caused the relay to go bad (Too much on/off). I REALLY don't want to think about a fuseable link being bad. That's WAYYY too much wiring chasing for me on a daily driver.

naf

iTrader: (7)

You know the fan motor's good, so try jumping the two fat leads on the relay connector with a fairly stout gage of wire, like vetteoz suggested. This will check the power leads to and from the relay.

The 12V hot in 'run' lead may also be fused through a small fuse like the diagram above says. You can check it at the relay connector with a meter or a test light.

Not the switch if shorting the switch lead to ground doesn't work.

vetteoz

iTrader: (13)

That circuit is protected by the fusible link shown

Ozz1967

iTrader: (4)

I grounded the two fat wires...the red and black one. The fan kicked on.


If I've followed that means the in-line fuse is good right? Possibly the relay is bad. Also possible the "new" relay is bad.

However, I am going to start by taking my new switch back out and removing all the teflon tape from it and re-installing it. It's possible (as mentioned earlier) the teflon tape is preventing the switch from grounding to the engine and completing the circuit.

Any other thoughts