2nd fan question

[Cashmunson]

does the AC relay control the 2nd fan? mine isn't turning on and i'm trying to figure out why.

[llwood]

thats what i was always told.....

[Jeremy]

No, there should be two possibilties for secondary fan control.. the A/C pressure switch, and the fan switch in the passenger head. So when the A/C is running it closes the switch, grounds the secondary fan relay, and turns the fan on. Or, the fan switch sees its predetermined temperature, and grounds the secondary fan relay.

So, first step would be to eliminate the relay. If your primary fan is working, then it is probably safe to say your fusible link and ground are both okay. Unhook the connector to the relay and, using a fused jumper, connect the constant power (orange) and the positive lead that goes to the fan (black/pink). I'm going off of a 1991 Firebird service manual, so yours should be the same. If your car blows up during this step, I apologize. The fan should turn on. If not, check for power and ground at the relay, and check the connection at the fan. Then you can plug the relay in and back probe or pierce the terminal with the green/white wire, and connect it to ground. If your fan turns on, then your relay is good, and your problem is on the control side. Maybe you just aren't reaching the 238* threshold and your A/C isn't charged, so the switch never closes. Or the A/C pressure switch is bad.

Simple.

Here are the diagrams. The first is for the main fan, and the second is for the secondary.

[Jeremy]

Oh and the fan switch isn't the one in the accumulator on the firewall, that is the cycling switch. The fan switch is on the back of the compressor.

[Cashmunson]

jeremy my car has no ac equipment at all. the previous owner installed a heater only box, all i have left is wiring. and what wires are left, is a real hackjob. alot of wires aren't the original colors, and alot of the connectors have been broken or cut off. the previous owner actually used duct tape for all wiring instead of electrical tape or actual connectors.

what i was actually thinking about doing, was this:

cut the second fan wiring out of the circuit. get another fan control relay like the first fan uses, wire the relay and fan in parallel with the first fan in that circuit, so they run together.

[Jeremy]

That would work, if that is what you want. If the wiring between the relay and the fan is destroyed or questionable, you could easily run a new wire from the fan to a new relay. Set the relay up with its own constant power, switched power, and ground and trigger it with the same green/white wire going to the primary fan relay, and you're set. Or you could think about wiring it to a new fan switch in the head (at whatever temp you want).

This is all assuming the condition that the wiring is cut and unrecognizable, otherwise all the wiring you need for the fan to work is already connected to an existing relay, so it would be a lot easier to check/repair those connections if possible.