Here goes...

87 T/A
305 TPI w/dual cooling fans, passenger side one does not work

Alright, I've read all the old posts about what all controls the secondary fan (a/c switch, temp switch between #6 and #8, ect), and followed the haynes book fan circuit diagnostic. Here is what I have come up with. The fan motor and relay are good. The problem seems to lie in the wiring that causes the relay to switch. The center two terminals on the fan relay are a tan wire and a green wire. The tan wire should have 12V applied to it when the A/C switch is on, and the green wire should be ground (if I understand everything correctly). Well, my tan wire has 12V, but I the green is not continuous with any ground. So, I figure that there is something wrong with that green wire in between the fan relay and wherever it goes. You guys agree with my thinking? I'm hoping somebody knows where that wire goes. Oh yeah, the primary fan on the driver's side works just fine. Its just that the passenger side fan never comes on. Any ideas?

 

On my 87 formula (305 tpi dual fan), the passenger fan only came on by way of the temp switch in the passenger head. Everything else called the drivers side fan. The tan wire should power up with the ignition in the run position.

------------------

• my Formula Homepage
• Collision P/Ns & Diagrams (Nearly complete now!)

The mind is like a parachute, it only works when its open

 

Am I correct in thinking that the passenger fan is supposed to come on when:
a)engine gets really hot (don't remember the actual temp)

b)a/c gets turned on (at any temp)


But yeah, I haven't checked the temp switch yet. Hopefully I'll get around to that tomorrow. Thanks

 

Depending on which fan diagram you look at(unless the book has been updated since I bought mine), one shows the A/C pressure switch ('87, F code) hooked into the ECM, if you were to unplug the pressure switch (on the pass. side line running on the frame) & start the car, the drivers fan should start running as soon as the engine is running (as was the case with why my fan never shut off when I 1st got my car running).

The other (ECM diag) only shows where the relay is controlled by the ECM. Neither diagrams shows the 2nd fan. Not all fan setups were exactly the same though throughout the years but, I'd guess yours wouldn't differ from mine being same year/engine.

I've been thru & rerouted 95% my wiring & the passenger fan was hooked up only to the temp switch on the engine (on my car). The JET fan switch replaces this with one that grounds at a lower temp (205°) instead of the insanely high temp the other switch does (which is higher than what the ECM switches the fan on at).