Newbie cooling fan test question

[Da Flash]

My '92 has recently started to overheat. I've narrowed it down to the fan not coming on except when I turn the car off. I have tested the fan but, it will only come on when I jumper switch B (the one in the thermostat housing), when I jumper switch A (the one under the distributor) and turn the key to on, the fan doesn't kick on.

Is this normal? If not, what might it indicate?

TIA

[dj_ender]

Yes, that's normal. Jumping the ECT won't activate the fans. Change the fan switch in the thermo housing.

[Da Flash]

Yes, that's normal. Jumping the ECT won't activate the fans. Change the fan switch in the thermo housing.

I changed the switch for a "used" one from the JY. I'll look into getting a new one or testing the two that I have. Testing them requires boiling water I think.


Thanks!

[dj_ender]

Well if you can trigger the fans by jumping the connector, it's either the switch, or the fan timer. But my money is on the switch.

[illinois_erik]

if your car is over heating while driving, you have bigger issues then just a faulty switch. the fans more for like if youre sitting in a traffic jam for 20 minutes, even then itll turn on and off sporadically. if the inside of the radiator is all crusty with deposits id start looking for a replacement, or if you can afford the downtime, take it out, seal it up fill it with white vinegar and water and let it sit about 36 hours, then flush it out with clean water. or one of those flush kits with the citric acid you drive around on for a few hundred miles.

[F22Chris]

Don't rule out the harness. I had a similar issue a while back. But t was only at idle. My switch was fine, but the fan connector would only turn the fan on if I bent the wires to the right. So I zip tied the wires in a wonky position. That worked till I totaled the car.

[Da Flash]

if your car is over heating while driving, you have bigger issues then just a faulty switch. the fans more for like if youre sitting in a traffic jam for 20 minutes, even then itll turn on and off sporadically. if the inside of the radiator is all crusty with deposits id start looking for a replacement, or if you can afford the downtime, take it out, seal it up fill it with white vinegar and water and let it sit about 36 hours, then flush it out with clean water. or one of those flush kits with the citric acid you drive around on for a few hundred miles.

You bring up an interesting point. The car will heat up after a 5 mile trip down the freeway drop off my son and 5 mile trip back. I'll have to look into the radiator/thermostat.

[illinois_erik]

You bring up an interesting point. The car will heat up after a 5 mile trip down the freeway drop off my son and 5 mile trip back. I'll have to look into the radiator/thermostat.

i try :P a little experiment that might suck, is to do your run but with the heat fully cranked and see if that helps keep the temp down even a little bit, this will show that your radiator has lost cooling efficiency. if it has no effect then the next thing would be to check the thermostat, or even try it with it absent since its warm out now.

[tougeteg]

if your car is over heating while driving, you have bigger issues then just a faulty switch. the fans more for like if youre sitting in a traffic jam for 20 minutes, even then itll turn on and off sporadically. if the inside of the radiator is all crusty with deposits id start looking for a replacement, or if you can afford the downtime, take it out, seal it up fill it with white vinegar and water and let it sit about 36 hours, then flush it out with clean water. or one of those flush kits with the citric acid you drive around on for a few hundred miles.

agreed illinois_erik I've experienced similar issues with my cars in the past. to the OP have you checked for any coolant leaks? usually driving with no fan at speeds 50mph or more in my experience will keep temperatures from pegging out. as illinois_erik stated the cooling fans primarily are used when idling in traffic or initial start up in winters to heat your vehicle and for keeping the a/c condenser cool when running your a/c. have you checked your thermostat? if its frozen shut you will notice a significant overheat. sorry to state the obvious. just want to make sure all your bases are covered. if your thermostat is working properly. try to do a cheap super flush. buy a chemical coolant flush, or two, I recently did one myself and used two. and a couple gallons of 50/50 coolant. or concentrate your choice. and then around 3-4 gallons of distilled water. make sure its distilled to keep any minerals/corrosion accelerating composites in tap/spring water aren't in your coolant system. run the chemical flush through your engine with the old coolant. drain as much you can (I personally backed my car onto wheel ramps to make sure as much coolant could come out as possible) then refill your car with the distilled, let it run through the coolant system for a few minutes. till the temp gauge starts reading. then drain and refill. repeat with the water until theres almost no green from the original coolant, then add the second chemical flush. run it, drain it again, and refill with your new coolant. you will want to drain it at least once after filling it with your new coolant if you use 50/50. I used concentrate because of the water in the system and mixed as close to 50/50 as possible. hopefully it will clear any blockages in your system and clear corrosion. if not, then look into a new rad. and check for any bad hoses/pinched hoses.

something I forgot to ask originally but when was the timing belt and water pump last replaced? if the pump is bad and coolant is not circulating you will overheat. and can end up with a continual coolant system problem if the fins from the pump continue through the system if the pump is damaged.

best of luck!

[Da Flash]

i try :P a little experiment that might suck, is to do your run but with the heat fully cranked and see if that helps keep the temp down even a little bit, this will show that your radiator has lost cooling efficiency. if it has no effect then the next thing would be to check the thermostat, or even try it with it absent since its warm out now.

Thanks for the reply, turning the heater on does keep the water temp at around the mid point. Looks like I have to look into the switch and the radiator/thermostat. I got hung up on the fact that the fan doesn't come on.

[Da Flash]

agreed illinois_erik I've experienced similar issues with my cars in the past. to the OP have you checked for any coolant leaks? usually driving with no fan at speeds 50mph or more in my experience will keep temperatures from pegging out. as illinois_erik stated the cooling fans primarily are used when idling in traffic or initial start up in winters to heat your vehicle and for keeping the a/c condenser cool when running your a/c. have you checked your thermostat? if its frozen shut you will notice a significant overheat. sorry to state the obvious. just want to make sure all your bases are covered. if your thermostat is working properly. try to do a cheap super flush. buy a chemical coolant flush, or two, I recently did one myself and used two. and a couple gallons of 50/50 coolant. or concentrate your choice. and then around 3-4 gallons of distilled water. make sure its distilled to keep any minerals/corrosion accelerating composites in tap/spring water aren't in your coolant system. run the chemical flush through your engine with the old coolant. drain as much you can (I personally backed my car onto wheel ramps to make sure as much coolant could come out as possible) then refill your car with the distilled, let it run through the coolant system for a few minutes. till the temp gauge starts reading. then drain and refill. repeat with the water until theres almost no green from the original coolant, then add the second chemical flush. run it, drain it again, and refill with your new coolant. you will want to drain it at least once after filling it with your new coolant if you use 50/50. I used concentrate because of the water in the system and mixed as close to 50/50 as possible. hopefully it will clear any blockages in your system and clear corrosion. if not, then look into a new rad. and check for any bad hoses/pinched hoses.

something I forgot to ask originally but when was the timing belt and water pump last replaced? if the pump is bad and coolant is not circulating you will overheat. and can end up with a continual coolant system problem if the fins from the pump continue through the system if the pump is damaged.

best of luck!

Off to the parts store for a new switch and some radiator flush, I'll keep you guys posted!!

Thanks!

[Da Flash]

So, how many temp switches are there?

I finally got some time to tinker with the car, I pulled the thermostat. It tested good but, for less than $10, I bought a new one. Now I realized that there are 3 (4 if you include the switch for the temp gauge) sensors!!!! One on the outlet at the front of the engine, one on the thermostat housing near the rear and one right next to the gauge sensor under the distributor.

I can jumper the one at the front of the engine to get the fan to come on, if I jumper the one under the distributor, or the one that goes in the thermostat housing, the fan doesn't

From looking at the FSM, it appears that switch "A" is the one at the front of the engine and the one in the thermostat housing is switch "B". What is the other one under the distributor called and what does it do???

Last but not least, where exactly is the "cooling fan timer unit" located? Inside the cabin or engine bay?

TIA!!

[dj_ender]

The sensor under the distributor is the ECT sensor ( Engine Coolant Temp ), and as I stated before, jumping it WILL NOT turn on the fan. The fan switch at the front of the engine is the high temp switch, it is the sensor responsible for kicking the fans on if the low temp switch (the one in the thermo housing) fails.

Since your fan doesn't kick on when you jump the fan switch in the housing, then you may have bad wiring to the fan or a bad fan timer. Do both fans come on when you jump the front switch?

[Da Flash]

The sensor under the distributor is the ECT sensor ( Engine Coolant Temp ), and as I stated before, jumping it WILL NOT turn on the fan. The fan switch at the front of the engine is the high temp switch, it is the sensor responsible for kicking the fans on if the low temp switch (the one in the thermo housing) fails.

Since your fan doesn't kick on when you jump the fan switch in the housing, then you may have bad wiring to the fan or a bad fan timer. Do both fans come on when you jump the front switch?

No, only the fan on the passenger side comes on when I jump the front switch.

I'm still trying to figure out exactly where the timer unit is.

[dj_ender]

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