electric fans
Thread Starter
Junior Member
Joined: Oct 2005
Posts: 70
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From: Henderson,Texas
Car: 87 iroc z28
Engine: 5.7 TPI
Transmission: 700R4
electric fans
I'm sure this has been beat into the ground, but I couldn't find any thread to help short of directly wiring the fans to a toggle switch. I cannot get my fans to come on! AT ALL! I tried running a wire between the A & B terminal at the ALDL, NOTHING. I tried turning my a/c on, NOTHING. I then removed the wire from the fan switch and grounded it on the exhaust. I heard the relay working but the fan did not turn. Please, someone help me figure this bull out. I haven't driven the car in about a year and I really want to drive it again.
Re: electric fans
You said you got your relay to click.
So start by seeing if you have power to the relay for the fan.
Then ground your wire again, and see if you have power to the fans.
If so try running a jumper wire from fan(s) to the bat and see if they work.
So start by seeing if you have power to the relay for the fan.
Then ground your wire again, and see if you have power to the fans.
If so try running a jumper wire from fan(s) to the bat and see if they work.
Thread Starter
Junior Member
Joined: Oct 2005
Posts: 70
Likes: 0
From: Henderson,Texas
Car: 87 iroc z28
Engine: 5.7 TPI
Transmission: 700R4
Re: electric fans
Ok, first off i burned the fire out of my thumb checking the power to the fans. I bypassed the relays for the fans to check for power and if the fans actually work. They have power and work fine when the relays are bypassed. Now, since I'm such a dummie, I really don't know what that means. I think it means that the relays are bad, am I right? Now here's something I really don't understand. Each fan runs seperately, each has it's own relay. The primary is controlled by the ECM and the secondary by the fan switch. When I bypassed either relay, it didn't matter which one, both fans came on. Is that supposed to be how they work? Are my relays bad?
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Joined: Jul 2008
Posts: 76
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From: VA
Car: 1990 IROC
Engine: 5.7 TPI
Transmission: T-56
Re: electric fans
The cooling fans are to run separate. The one on the drivers side is controlled by the ecm and the pass. side is controlled by the fan switch. If you have a multimeter, (you can get one at Radio Shack $30) under the dash where the fuse panel is located you'll see a black box along the firewall. Look for a two orange wires that have other wires going out. The outgoing wires should be black/red. The orange wire is hot at all times when you turn the ignition switch on. This signal only supplies power to the fans when the relay is closed. The only thing these relays are looking for is a ground to close the relay. The primary relay ground closes when the ecm tells it too by responding to the signal from the cool temp sensor on the manifold. The secondary fan relay closes when the cool fan switch reaches a temp. Mine comes on when the car reaches about 235. There is also a fan pressure switch that controls the secondary fan as well for the ac. Its located next to the battery. One more thing you could look at is, there is a inline fuse next to the battery. Its encased in a plug. Check to make sure that isn't blown either. You said you heard a clicking when you grounded out the wires right, that means that the relay is working like it should, you just don't have power going through the relay when the switch closes. Take the multimeter and shoot for power at the inline fuse I described eariler. If nothing is there then shoot for power at the relay on the orange wire.
Last edited by Kodfish; Oct 5, 2008 at 10:02 PM. Reason: Added some detail
Senior Member
Joined: Jun 2008
Posts: 1,298
Likes: 2
From: Norfolk VA
Car: 85 Camaro IROC
Engine: 5.7 TPI
Transmission: 700-R4
Axle/Gears: open rear, 3.42 gears
Re: electric fans
you hit the nail on the head.
if the fans work when hardwired to the battery, but not when you force the relay to actuate, then your relay is bad.
bring them both in to autozone or whatver and say, i need one of these.
you can be sure and take the cover off the relay and use an insulated rubber tool of some kind to manually shut the relay and see if that fixes the problem.
if it does, than your relays are ok and its in the wiring leading up to the relays.
you really shouldnt need a multimeter for this.
if the fans work when hardwired to the battery, but not when you force the relay to actuate, then your relay is bad.
bring them both in to autozone or whatver and say, i need one of these.
you can be sure and take the cover off the relay and use an insulated rubber tool of some kind to manually shut the relay and see if that fixes the problem.
if it does, than your relays are ok and its in the wiring leading up to the relays.
you really shouldnt need a multimeter for this.
Thread Starter
Junior Member
Joined: Oct 2005
Posts: 70
Likes: 0
From: Henderson,Texas
Car: 87 iroc z28
Engine: 5.7 TPI
Transmission: 700R4
Re: electric fans
Shouldn't the fan who's relay I bypassed be the that comes on and not both. I believe that some alterations have been made to the orig. wiring. I tried to trace the problem without success, so I took an old relay that I had lying around and wired it to bridge the three connectors and turn the fans on when the car is turned on. The fans stay on regardless of the temp. or what the ECM says.
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