Hello fellow probe owners! Like most posters, I'm looking for some expertise and or advice on why my 96 SE overheats now and then and more often after it sits on a hot day after driving.(I drive it again and thts when the FAN REFUSES TO TURN ON) I know a bit about cars and I know for a fact the fan does not come on when it does start to overheat. When its cool out the fan works fine. Right before it starts to overheat, the A/C quits working and starts cycling as well. I changed the thermostat, fan relay, checked all fuses, and just orderes a coolent temp sensor. The fan works fine when jumped ddirect to battery. There is no noticable coolent loss and the radiator is fairly new. Any help would be awesome. I'm all out of ideas. I would like to keep the car until it hits 300K if possible,,, Help help help
I don't think the coolant temp sensor is your problem. Normally when these sensors stop working, the computer assumes your car IS overheating and turns the fan to maximum speed. You say you know a bit about cars so here's a couple of things you can check.
First off, as a general rule, most cars don't just have one fan relay, they have a bank of relays or a dedicated module, so that the computer can select different speeds for the fan. I don't remember exactly how many in your model because I haven't worked on one of those for a while but I'm pretty sure it doesn't have a module. Double check, this because the fact that the fan doesn't work only when it's hot could indicate a sticky relay. Next, do a resistance check in the fan windings and in the wiring loom between relay and fan. Resistance in most materials increases with temperature. If you have high resistance in the wiring loom (due to corroded conectors, etc), then you'll be loosing a part of whatever voltage should be getting to the fan and this will only get worse the hotter it gets. This could be why your fan works when jumped directly from the battery and not when the relays give it power.
If all this is good, wait for the car to overheat and check what voltage (if any) is getting to the actual fan connector. If the voltage is good, it'll be a fan problem, if not, check the voltage at the relay, if there's voltage there and the relay is good then the problem will be in the wiring between fan and relay.
If there is no voltage getting to the relay either your PCM is not receiving the coolant temp sensor signal or it's damaged. Check this by disconnecting the coolant temp sensor with the engine running, your fan should kick in momentarily at max. speed.
Hope I didn't confuse you too much. Feel free to ask any questions, cheers
Thanks for the advice and help, I'm going to troubleshoot again this weekend.(I hope its Hot enough out to duplicate)
I'll write back with the results, I didnt know there could be another fan relay so I'll be chasing wires as well. When the A/C turns on the fan should click on so Ill also test with the A/C on.What you said makes complete sense with the wire resistance when its hot. I'm not sure, but when I disconnected the coolent temp sensor last time I dont think the fan came on at all so I'll be checking that again as well.
hello again everyone
For those of you following the cooling problem, I thought I'd post a bit of progress or lack of it. I went ahead and tried to duplicate the overheating this afternoon by disconnecting the coolent temp sensor, upon doing so, the fan came on for a second and stopped. With the sensor unplugged the a/c would not come on wich is normal. I let the car sit at idle with the hood down for over a half hour and i could not get the car to overheat!!!!!! garage temp was 75F........with no fan it would not get hot and stayed in normal range, not even a sign over overheating.!!! Plugged sensor back in and fan kicked on like normal for a bit then shut down as normal. A/C was now turning on and fan as well(w/A/C on).. RESULT The Probe will most likely overheat on days over 90f I can only wait for another hot California Day to troubleshoot. I continue to drive the car with 291,000 miles on it approx 90 miles a day.
It just occurred to me that after reading your last post that the problem may be in the high-speed circuit of the fan. The low-speed seems to be fine and then when the high-speed should kick in (like when disconnecting the coolant temp sensor) nothing happens. Did you find a second relay for the fan in your owner's manual ?
So far the only fan relay I've found and replaced was the one forward of the radiator. I'll have to check out the book again but I'm failry certain it only showed one but i could be wrong. When the fan does turn on it seems its at high speed (sound & Speed of the air) Operationaly, I've never seen the fan operate except @ what appears to be the High-speed. Yesterday when I disconnected the Cool temp sensor it barely turned on so I couldnt tell what speed. SO with the temp sensor disconnected it should come on High speed???? If so thats got to be whats wrong. It is for sure a two speed fan because of the 3 wires. I'll go direct to battery with both to make sure the fan operates in both speeds.
OK, don't stress bro.
See if by any chance you have less legs on the relay than on the connector it sits in. Sometimes people put 3-4 legs relay where there should be a 4-5 one. Be carefull not to short circuit the fan when testing it. If you still can't find anything wrong give until Monday and I'll try to unearth a Probe manual and have a look at it if I have the time. How's that sound?
The relay I replaced was the factory relay that plugged right in. I replaced it with new one OEM "mazda on the box" relay. As for the fan it tested OK with low and high speed. And oh ya those wires come close when testing the fan. It should be hot today so I'll see if I can check voltage when she overheats..
I appreciate all the help.
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