I have a 90 efi corolla, both my radiator and ac fans will stay on when the key is turned to on. ive read a few threads and have seen people say its the relay/fan switch/sender/sensor. can anybody tell me how i could test these things to figure out what is really causing the problem. I have found the relay/the sender and sensor on the thermo housing and what look like two additional temp sensors.
car is completely stock, new battery, ac is not on,new coolant, on cold engine
The radiator fan is "fail safe on", and it's circuit runs through the A/C high/low pressure switch.
If there is a break in the circuit, (including a bad fan thermo switch) the radiator fan will stay on.
The fact that the A/C fan is on also, makes me think that the A/C high/low switch is bad.
The radiator fan switch is the one that hs the white connector with one wire in the last photo.
The A/C high/low pressure switch is over on the right side of the engine bay on the A/C pipe just forward of the firewall.
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'88 Corolla, AE92 SR-5, 7A-FE swap/GT-S suspension
'87 Corolla, AE82 FX-16, 4A-GZE swap (autocrosser)
'03 Tundra 4X4 Access Cab, (FX tow vehicle/Home Depot runner)
Modification: Changing something to what you thought it should have been from the start!
Last edited by Donald; 11-07-2011 at 06:17 PM.
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in the second picture there is nothing hooked up to that coolant sensor... I don't think that's actually a sensor for the radiator fan, but I would definitely fix it.
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The Following User Says Thank You to eage8 For This Useful Post:
The radiator fan is "fail safe on", and it's circuit runs through the A/C high/low pressure switch.
If there is a break in the circuit, (including a bad fan thermo switch) the radiator fan will stay on.
The fact that the A/C fan is on also, makes me think that the A/C high/low switch is bad.
The radiator fan switch is the one that hs the white connector with one wire in the last photo.
The A/C high/low pressure switch is over on the right side of the engine bay on the A/C pipe just forward of the firewall.
which of these two would be the high/low switch? how could i test it to see if that's causing the problem, thanks.
Quote:
Originally Posted by eage8
in the second picture there is nothing hooked up to that coolant sensor... I don't think that's actually a sensor for the radiator fan, but I would definitely fix it.
was disconnected so i could clean it up for the picture but thanks
which of these two would be the high/low switch? how could i test it to see if that's causing the problem, thanks.
was disconnected so i could clean it up for the picture but thanks
I believe it is the on on the larger diameter line, but am not sure. I would need to check the manual. Will try and do that later.
Right now I need to make the most of the good weather to continue with stripping my wrecked car.
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'88 Corolla, AE92 SR-5, 7A-FE swap/GT-S suspension
'87 Corolla, AE82 FX-16, 4A-GZE swap (autocrosser)
'03 Tundra 4X4 Access Cab, (FX tow vehicle/Home Depot runner)
Modification: Changing something to what you thought it should have been from the start!
The Following User Says Thank You to Donald For This Useful Post:
The Dual pressure switch is on the larger diameter line. The high pressure switch is on the smaller line.
I will scan the page with the test procedure when I figure out what is wrong with my scanner. If not I will write the instructions, but bare with me. I've been really busy.
__________________
'88 Corolla, AE92 SR-5, 7A-FE swap/GT-S suspension
'87 Corolla, AE82 FX-16, 4A-GZE swap (autocrosser)
'03 Tundra 4X4 Access Cab, (FX tow vehicle/Home Depot runner)
Modification: Changing something to what you thought it should have been from the start!
__________________
'88 Corolla, AE92 SR-5, 7A-FE swap/GT-S suspension
'87 Corolla, AE82 FX-16, 4A-GZE swap (autocrosser)
'03 Tundra 4X4 Access Cab, (FX tow vehicle/Home Depot runner)
Modification: Changing something to what you thought it should have been from the start!
Donald is correct about the "fans on" issue being the result of the fail safe electrical design of the fan circuit. Any open circuit in the fan wiring can cause this issue.
In my experience, its usually either a bad connection to the coolant temperature sensor or a bad connection in the fan harness connector located below the battery tray. I usually just disconnect the connector located below the battery tray, clean the contacts, reconnect the two halves of the connector and the problem is solved.
90% of the time, the fans stay on because the thermostat is shot... have you tried a new one yet?
You mean "thermo switch" (fan switch) right? Not "thermostat".
__________________
'88 Corolla, AE92 SR-5, 7A-FE swap/GT-S suspension
'87 Corolla, AE82 FX-16, 4A-GZE swap (autocrosser)
'03 Tundra 4X4 Access Cab, (FX tow vehicle/Home Depot runner)
Modification: Changing something to what you thought it should have been from the start!
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