cooling fans/electical problem/3rd gen

I've got a 305 TPI with A/C, so I've got two cooling fans. Neither fan will work. I've checked the constant voltage coming into both of the fan relays and that voltage is 10.7. At the fuse block, it's putting out 12.3 - so I've got some resistance on that line, for sure, that I've not been able to figure out since it's all hidden in the wiring harness.

If I jumper the relay (bypass) by plugging a wire from the constant power to the positive feed for the fan (this is done at the relay plug - removed from the relay), the fan will not come on. This is the case for both fans. However, if I take a wire connected to the battery (12+ volts) and connect it to the positive feed for the fan (at the relay), the fan will work. Once again, both fans act the same here.

Is it true that these fans need a certain amount of volts (or amps) to start up? Is my problem the voltage drop between the fuse box and the relay? It's almost time to go racing (SCCA) and I need these fans working or it will toast the engine.

Thanks,
Paul C.

umm.. im not sure about that
but all i know is that i wired a wire straight from the battery to the fan in my 2.8 85 camaro...
and the FAN had a short in it. in the middle of chinatown, my car starts smoking.. i pull over, half in the road, pop the hood, more smoke >_< , i ripped the wires out with my bare hands (ouch..) and the outside insulation for it was alll melted.

yeah, i couldnt just turn off the switch..cuz my dad wired it INSIDE the car.. (Cuz it wasnt working and my car was overheating and i had to get somewhere really quick)

needless to say, i was pissed. i bought a new fan..wired my fan to the AC blwer, since i ripped out the AC...and viola. it works perfectly. you can even adjust the fan speed!!

haha

Well your problem obviously lies between the relays and the battery. Now you've checked your fuses I hope? I know it's simple, but I've seen people overlook that step.

Let me go look for my Haynes manual so I can see a wiring diagram.

Looking at this vague wiring diagram...

Things to check:

- 10A fan fuse, take it out and look at it
- Coolant fan relay
- Fan A/C pressure switch
^^ Those are on the control side of the circuit (they switch the relay closed)

The coolant fan circuit runs through the power control module (PCM), so I don't know how you would check that.

On the load side there's only:

- Fusible link 20 GA-RUST (?)
- The fan motor, which works.


This wiring diagram sucks, and it's only showing me one fan motor. But from what you've explained 10.7 shouldn't be enough to run the motor. It sounds like the problem is in the line between the relay and the fuse.

3KGT- Thanks for looking it up for me. :) I don't know how to explain the voltage loss from the fuse box to the relays. My mechanic friend said that it's possible that when a load is put on the circuit, that the 10.7 may bump down even further. I don't understand electricity completely, so that doesn't really make sense to ME, but I trust him.

Likely, what I will do is run a new wire, with in-line fuse to the source wire at the relays and be done with it. It would be nice to keep it all clean-looking, but this isn't a show car anyhow. hahahahaha FAR FROM IT, this car is a BEATER that I race at SCCA slaloms. The drivetrain is still all really good, though.

BTW, sweet lookin' car!

Thanks again,
Paul

hmm well just be careful its not actually the motor shorting out..cuz mine worked directly, but when u left it a lil while it totally fried everything (the wires)

Is it possible that the reason it isn't running when you jump the two wires at the relay because it doesn't have a ground, relays nornally have more then 2 wires going to them, is one a ground that the realy connects, hence when the relay is removed its not getting a ground to run the fan? Maybe its grounded somewhere else, I would check into that, or did you not have the relay hooked up when you jumped power to the fan to make it run? Most of the time electric fan problems are either a fuse or temp sensor problem, a haynes manual that happens to be opened up on an autozone shelf normally gives the info to test the sensor.

Ikey-

I appreciate the info. I went to pick up some wire and in-line fuse yesterday and the guy at AutoZone told me that cooling fans don't run on 12 volts, but something less than that. I need to check into that. He said that if you run 12 volts to the fan it will burn up. So, I need to find out something there before I run a new wire to the relays.

Gmack-

Thanks, but I've checked the grounds and they are fine. The grounds are run separately from the power. They go to the radiator support. If the grounds weren't good the fan wouldn't come on with power (only the positive) from the battery. Oh wait... maybe you're talking about the grounds that actuate the relay. Well, that shouldn't be the case because I've jumpered from the constant power to the feed for the fan at the relay connector - meaning, the connector is disconnected from the relay. With this jumper in place, the fan will not come on. That tells me (I think) that the power coming into the relay is not enough/sufficient to run the fan. Did I misunerstand you?

I'll do some more looking around. I'll do my best to post my findings here for others to see.

Thanks for the help, all!

Peace,
Paul