Ok so today while driving around downtown, the upper radiator hose on my 91 split and shot coolant everywhere. Now I know the fact that the hose was old and weak probably had something to do with it, but the engine was also overheating. The PO put a new rad in the thing and has the cooling fan wired to a sensitivity switch, and from that runs a thermometer to where the upper rad hose is clamped to the radiator. This system clearly isn't very reliable, so I am wondering what needs to be done to switch it back to where the fan is computer controlled.

Thanks

 

Hmm no input eh? I think im going to check the manual for a wiring diagram.

 

I assume you have the single fan just like mine. It was never computer controlled. There is a temperature fan switch in the passenger side head that provides a ground to the wire attached to it when the coolant reaches a certain temp. This wire goes to the fan relay over by the brake booster. When that green with white stripe wire is grounded, the relay sends 12V down the black with red stripe wire to the fan to actuate it. That's the whole deal. When the temp drops to the temp the switch was designed to cut off at, it stops. Different switches can vary the on-off temps . Lower than stock is often preferred. Returning to this setup depends on what the PO may have removed or altered . Have fun!

 

Ok so i took out the aftermarket fan switch and found two wires coming off the fan motor, I figure the fatter one is the power that leads to the battery and the thinner is the signal that leads to the fan switch. Found a black and WHITE wire coming off the fan relay that was cut. Hooked it up to the thinner wire leading to the fan motor and the fan started spinning. So i guess i've figured out the wiring, but the fan started up with the motor cold, so I guess the switch is shot (stuck grounded)?
Thanks henry for the useful information.

EDIT: You say you can get different temperature switches? Lower than stock is preferred? I'm not even sure what stock is. Can you recommend one?

 

There is no direct wire from the battery to the fan. Fan has two terminals. One for ground, and the other that gets positive via the fan relay

 

My mistake, the larger wire is grounded.

 

The bottom right part of this diagram has the fan system wiring. You may want to check it out
http://www.austinthirdgen.org/mkport..._engine_wiring

 

Oh yeah, forgot, here's some switch conversations you can find more by using the search feature. Highly recommended source to become familiar with
https://www.thirdgen.org/forums/cool...ernatives.html

 

Ok thanks. By the way, first link is broken.

 

Just go to www.austinthirdgen.org and navigate to where you need to go

 

any body got know the wireing for a 91 tpi dual fans po put fans on toggle switch