My car seems to be running hot. It gets to 220 sometimes 240 before the fan comes on. Today, the fan didnt come on at all. I have had several people tell me that it might be the fan switch (which I have no idea where it is), the relay for the fan and then the coolant temperature sensor.

I have no idea where to start. The coolant temperature sensor tells the fan when to come on right? and the fan relay switch sits up near the fire wall right? so where is the fan switch?

 

I also have a '91RS...only fan control is the fanswitch in the pass side head, between and a bit below #6 and #8 plugs...I've been told the turn on point is pretty high...in the 230-range.

CTS won't affect it, just for ECM info.

 

It never used to get this hot. So the Temp. Sending Unit doesn't have anything to do with the car getting to hot?

Fan switch regulates when the fan is supposed to come on?

 

personally i think the temp fan switch is bs, put in an aluminum radiator, water pump, 160 degree stat, and wire your fan so its always on with the ignition,of course if you drive it in the winter youll want to not go too extreme i beat the snot out of my car and it never goes over 180

 

ok well i dont have that much time on my hands, i just need to fix the problem and move on. i have absolutely no time to take out the old radiator order a new, switch out the thermo., etc.

any other suggestions? how likely is it that the fan switch is bad? or the relay? where is the relay for the fan? on the firewall which side?

again, does the coolant temp sensor have anything to do with the fan coming on? if not what controls it? the fan switch? the temp. sending unit?

 

Primary Coolant Fan Turn-On System
Factory Circuit Operation
On TPI engines, the primary fan is controlled by the ECM and A/C head pressure. The ECM grounds the coolant fan circuit when the coolant temperature sensor indicates the temperature is greater than 222° or when the A/C head pressure is greater than 232 psi and the vehicle speed is less than 35 or 40 mph (depending on application). When this circuit is grounded, the fan relay is energized and voltage is applied to the fan.

Secondary Coolant Fan Turn-On System
Factory Circuit Operation
On some applications, the secondary fan is controlled by the ECM, A/C pressure switch and a temperature sensor, similar to the primary fan. On other applications, the ECM is bypassed and only a temperature sensor is used.

read this:
https://www.thirdgen.org/newdesign/tech/cool.shtml

i order this, works great
http://www.madvet.com/shop?frame=1.138.944

 

Yuel, he doesn't have a TPI...so only a single fan setup...not ECM controlled....least as far as I can tell on my '91

Svanky,

You need to determine if the temp is accurate and if the fanswitch is working or not, or relay is flaky..

Relay should run about 10 bucks, fanswitch 15 (stock).

Relay is up on the firewall to the right of the brakebooster(facing) the engine...two relays...other is fuelpump, IIRC...

But most importantly, don't rely on the factory gauge..they can get whacky.

 

What about a TBI model?

 

she doesnt have a TPI.... LOL..... Thanks......

 

again , just cut the fan wire and rerun it to a switched source, your in florida so i doubt it gets cold enough to worry about it, no more relays , switches etc........im sure some frown on this approach but fan on all the time will cool it down

 

T.B.I. model Fan Relay is in the same place. Coincidentally, you can remove the wire from the fan switch and using some wire, run the wire up to the negative battery terminal to see if the fan comes on. If it does, and you want to, leave the wire connected to the negative terminal and the fan will come on whenever you turn the key to the on position. If the fan doesn't come on, your fan motor has probably gave up the ghost. Fixing the switch or relay is the correct way, but my wire idea is the poor man's way,lol.

 

if the thermostat is stuck in open loop does that affect when the fan should turn on? right now the fan doesn't come on until 240 then cools to 220. before it would come on at 220 and cool down to 200......

 

If all your getting is a slight difference in temperature reading, I'd hook up a mechanical gauge and see what it reads. The factory gauges are known for being off. Sometimes it's a little, sometimes it's a lot! Check with a mechanical gauge before automatically suspecting the fan switch or relay is bad.

 

i dont have access to all those tools. im just wondering why it is taking longer for the fan to come on now than it did three four weeks ago? i dont care if the gauge is wrong. its the same gauge that was in there before so something is obviously wrong.

is there a temp. setting on the fan switch that tells the fan when to come on? or would it have anything to do with the thermostat being stuck open? i started the car up with the cap off and the coolant is flowing from the minute i start it.

 

I think you missed the point. The fan switch tells the fans when to kick on based on the temperature it sees. Now if it sees 220 degrees, but your gauge inside the car says the temperature is 240 degrees, which one is wrong? The answer is the gauge in the car. Your fans are more than likely turning on at the right temperature. The fan switch and relay either work or they don't. If they don't, the fan won't come on at all. That's why I said that the gauge inside the car is probably wrong. The fan switch and relay can't just decide they want to wait to turn on the fan until the temperature reaches the new temperature they just decided is the new turn on point for the fans. Since you can only see the temp the gauge is displaying, you believe the fans are turning on later. The electronic gauges in these cars and all cars that use electronic gauges, right up to the brand new ones at a car dealership, don't have full sweep electronic gauges. This makes the information they relay undependable at best and completely wrong at the worst. I'd say your fan is probably turning on at 220 degrees still, but your gauge in the car says the temp is 240. Therefore, the gauge is wrong.

 

I understood what you were saying, however, you have stated yourself clearly this time around. Anyway, my question was directed towards the fan switch. Can you purchase a fan switch with a set temperature?

If I run the A/C, the cars temp stays around 185/190. If I wait for the fan to come on, the car runs at 220. For my sake, instead of risking overheating, I would rather have the car run at a lower temp, even if the gauge is wrong. Thus, the question is proposed..... When purchasing a new fan switch, are there different temp. settings or is there only one setting?

 

oh and back to my other question.... what happens if the thermostat is stuck in open loop?

 

If the thermostat is stuck open the car will run cooler, but it might affect the o2 readings. As to your other question. Yes, you can purchase the fan switch at different temp turn on points. Jet and hypertech both have them and they can be purchased through most autoparts stores, as well as Jegs and Summit catalogs and websites.