Ok i have a 91 camaro with the stock dual tpi fans, and an LT1 swap done.

My fans will not come on and i have no idea why. Here is what i have done

Both fan motors test good.
Primary fan plug gets 12v at about 220 degrees and has a solid ground.
Secondary fan plug gets 12 volts when my obd connector pins are jumped and has a solid ground.

Fans worked last fall, and spontaneously stopped working over the winter.

Fans dont come on. Why?

 

What you say doesn't seem to add up. If the fan motors test good (I assume you jumped them directly from a battery?) and both fan plugs show good voltage and good ground then they should work. The fact that the plugs show good voltage and ground suggests the relay(s) work fine. Have you pulled the connector(s) from the relay and fed 12volts to the fan power wire? If the fan plug is in place and the fan works then it's a mystery. If the fan doesn't work maybe there's an issue with the plug connecting with the pins in the fan motor connector. Make sure they are all straight and clean etc.

 

i know it doesnt add up. I literaly use a volt meter, get 12v, a good ground, and plug it in to the fan and nothing happens. Yet when i directly apply 12v and a good ground the fan runs. Another wierd thing is, i tested one of my fan motors while it was in the car, and it didnt work, yet when i pulled the motor out to replace it, i tested it again and it worked. I dont understand. I will try that relay trick, and will go back through everything.

Where would be the best place to check if the fans are getting a good ground? The neg bat cable?

 

Your v-meter leads should reach from the fan plug ground wire to the -ve battery terminal and there should be more or less zero resistance. ie good ground. If the fan motor didn't work in the car but did when you took it out that suggests some sort of issue with the fan motor. But you say it works when you apply battery directly to the fan. ???

 

The way everything looks the fans should work. I get about .4 ohm reading and about 11.5v to both plugs, and both fans work. Is there something else that would tell the fans not to come on? Like a switch or something?

 

could it be the tempature sensor?

 

I don't think so because I don't get voltage to the plug until the engine gets to about 220 degrees

 

well, maiby its the computer, i know its a long shot, but im just guessing, keeaping this thead active lol

 

Find the relays (firewall?) and pull the connectors off. There should be at least two small and two large wires. With the engine running check the voltage at the wires. One small and one large should have 12v. You can neg probe to the -ve battery terminal. The large wire that does not have 12v should be the lead that goes to the fan. Jump from +ve battery to that wire. The fan should come on. Then you can test the relay. The small wire that didn't have 12v should be the 'trigger' wire. Get a pin and push it through the wire or cut the insulation to get to the wire. With the engine running ground that wire. It should turn on the relay and the fan. If that doesn't work it's back to checking all wires and connections. Of course the above should be verified against your particular wiring diagrams. You have a Chilton manual?

 

your ground can ckeck good and still have a problem. the fans ground go thru a black multi-connector mounted on the frame below the compressor.(not thru the relay). a lot of times this ground connection errodes and causes exactly the problem you described. if so, you can simply re-ground the wires to a new good ground. these fan motors rarely go bad. hope this helps.

 

well my best guess is the connection with the plug to fan wasnt very good, i cleaned them up a bit and problem solved. thanks for the help!

 

well the fans worked properly for a while and then problem started again, so now im going to go through the trouble shooting you guys have posted. keep ideas coming, ill keep you posted.

 

just noticed something i thought was strange. i kept the fan connector hooked up to the volt meter as i was messing around with all my grounds and i noticed that the voltage read by the meter keeps increasing 0.1v at a time. going up one about every couple minutes. could somebody try to explain this to me?

 

Ok i did a little bit of testing

I started the car and took the primary fan relay off its plug.

There are 2 big wires, one orange and one black with a pink stripe.
There are 2 small wires, one green and one brown.

With the car running, neither of the big wires had a good 12volts.
The small green wire flashed up to 12 or 13 volts for a split second and then went blank. Could be a bad connection i guess.

I jumped the black wire with the pink stripe to the pos on the battery and the fan turned on.

If i did not get a good 12 on the big orange wire, does that mean there is likley a disruption in the wiring somewhere for that wire?

Thanks for any help

 

Solved.

The wire that goes to the + terminal on the battery that supplies the fan relays with the constant 12v was compromised. The wire was weak on one side of the original solder, with only about 3 or 4 strands of wire still intact in a 16 gauge wire.

Put a new inline fuse with a 20 amp fuse in, some crimp connectors, and fans are working again!