my single fan 91 305 rs had an overheating issue due to a defective fan-motor; replaced it, after that was solved i encountered another issue, now the fan only turns on right before the overheating point in the last 1/4 of the temp guage. so the question is what is wrong, is it a malfunctioning sensor...........?

 

Your fan isn't supposed to turn on until about 230 degrees so that sounds about right.

 

Yeah, I have the same problem, no fan until right before it gets to the red. Its really nervewrecking.

 

Yea mine did the same thing. just wire in a manual switch so you can turn them on whenever.

 

Yea you can wire in a switch like shane said or hypertech makes a fan sensor that goes in the head to replace the stock one that comes on at 186 i believe.

 

green92 before the overheating incident the fan engaged @ 160 or at least the temp guage never marked anything over and now it turns on @240-250 aprox so would the problem be the switch?

 

check the temp sensor i have a 91 rs and never had that problem at all the gauge always stayed normal and the fan came on

 

Check your temp sending unit which is in the driver side head sounds like it may be causing you problems by the gauge showing 160 when the fan engaged and now it shows 240 before the fan comes on. Like thirdgen said the oe setting is around the 230-240 mark. So its possible that your car has always been hitting that oe mark before the fan came on but your gauge was showing 160.

 

What would cause a fan NOT to turn on period, not at 230, not at start... etc.

originally it would turn on AS SOON AS THE KEY WAS TURNED, not it doesnt turn on period, not one of the fuses under the consol are blown

 

If you still have ac in the car when it is turned on the fan automatically comes on. If it is not coming on it could be the fan motor, but it also sounds like your fan sending unit is bad.

 

If your fan used to come on as soon as the car was turned on that meant it has been rewired. Either the wiring is messed up somewhere or your fan motor is probably bad. It could be the relay but most people tend to bypass that when they wire the fan to run off the ignition. If you need a fan we have them available on our website but I would start by checking the wiring.

 

What is the tool that is required to check the relays? and where are the relays under the hood on the 91? (i thought they were where they were on my old 4th gen but i was wrong)

And would possibly taking a volt meter to the plug and seeing if the fan is getting power prove that the motor is bad?

 

If the fuses are good, a bad fan relay, a bad fan or a bad temp sensor.

I believe the relays are prone to having a meltdown. I tried to replace mine with one from a junk yard and found that all 5 vehicles in the yard had the connector pack melted where it plugs into the relay.

Mine is located on drivers side firewall, closest to the fender.

Once you find the relay, pull the plug and check for voltage, if you have 12v+, jump power across it to see if the fan comes on. If it does, get a new relay. Their fairly cheap and easy to get (I think mine was $15)