2001 Cooling Fans Always Running - Toyota Corolla, Chevy Prizm (1998-2008)

This one has me stumped! 2001 1.8 ce with 3spd auto, both cooling fans are on as soon as the key is in the "on" position. It doesn't matter if the ac is on or not, and everything else is working great. I have 82k on the car, completely stock, and I first noticed the problem at 66k. I checked everything that the factory manual suggested, including all the relays. Both fans seem to be running at high speed, and the current solution has been to unplug both fans for the winter(very cold here till May).

HELP!!! Anyone ever heard of this before? The toyota dealer parts department said this year has no engine coolant temperature switch???? What turns on the fans then? Factory manual shows switch under alternator at the hose connection, but none on this year.

Thanks

ever_green

I'm not sure what you mean by cooling fan are you talking about radiators cause they are always running for me too. 2000 ve

I'm pretty sure they are not supposed to run all the time. The shop manual show tests to verify that they turn on at the correct coolant temp, and both running all the time in the middle of winter is not right. You may have a similar problem, and I did notice a slight fuel economy improvement with the fans unplugged. The check engine light came on once for this problem, but it was with the fans still connected when it was 1 degree outside.

I hope we both find a solution (if it is even a problem).

Dealership is incorrect, this car does have an engine coolant temperature switch (ECT switch). It is located on the thermostat housing, front of the engine, by the alternator and to the left of the intake manifold runners, can't miss it. In fact, from what I've seen, all the 1ZZ-FE have this temperature switch.

By default, if the switch fails, the fans will run constantly. First, double check that the connection is on tight and there is no corrosion inside the connection. Sometimes re-seating the connection is enough to clean off the contacts and restore operation. If that is the case, just use some dielectric grease or silicone spray to keep moisture out of the connection in the future. If you have a multimeter handy, you can check the resistance of the sensor. Sensor connection to good chassis ground should be no continuity when cold (below 83C or 181F) and show continuity when hot (above 93C or 199F). If the continuity is not as show above, just replace the sensor - 25ft.lbs is the torque that you need to reinstall it, if you haven't replaced the coolant, now would be a good time to do so. If you just recently changed the coolant, you can replace the ECT without too much coolant spilling out, just need to be quick about it.

ever_green

lol there is a problem i didnt know about. however my fans do change speeds sometimes they are louder and sometimes they are less prudent but they are ALWAYS running. this has been so since day 1 and has become more pronounced since i removed the hood insulator. I don't really mind since it keeps the engine cool.

Thanks for the replies! Well, this one is weird! I joined TIS for 2 days to get the best help I could, and that site is amazing. It was, however, wrong about the ect. I pulled the alternator, and there is no ect at the inlet pipe for the lower coolant hose, not even a raised boss or a threaded hole, just what looks like a thermostat housing. The wiring diagram I pulled up for the cooling fans shows nothing for the ect, so I pulled up the wd for the engine controls, and it showed the ect as a thermistor only, no switch!! I put the alt back together, and went through every test listed for every relay, fuse, and sensor, and found that while checking the incoming voltage for the triple pressure switch with a test light, the fans went off. I then traced the light green wire all the way to the ect, and could still shut off the fans with a test light at the ect. I pulled the circuit board out and looked at it, and found a corroded solder joint in the circut printed "fan". I went to a well organized wrecking yard and found a ecu for 100 bucks, and the counterman let me test it in the parking lot before having to buy it (I plugged in the old ecu to drive it to the parts palace). It shut the fans off, and now all is well!!!

Btw, if it matters on the lack of ect switch, my build date is aug 2000, sold as 2001 model year. I hope this helps somebody someday!

Thanks again!

Really - that is bizarre, good to know! Thanks for posting up the build date for the non-ECT unit. Wondering now if this is a regional thing / port installed, running change thing - maybe even bundled as part of a package, ie. cold weather package, enhanced cooling package for towing.

I knew about the thermistor, can be used as a switch, but being so temperature and EM sensitive - makes it sort of dodgy. Good diagnostic work, so you have to run it all the way to the ECM! That is very unusual to have it corrode like that. Those boards are supposed to be covered with a conformal coating that "seals" the moisture out. But I guess you can't really do anything to the contacts portion without compromising connectivity.