Fishexpo - Please Help - 91 Tercel - Radiator Fan Runs Constantly - Toyotas that aren’t Corollas

Hi Fishexpo. I know you can help me with this.

1991 Tercel, 3ee, auto

During the process of detailing the engine bay, I decided to remove all of the under-hood a/c components that haven't worked for years. Everything came out cleanly, and I taped up all of the remaining a/c electrical connectors left in the engine bay.

Finished the detailing and started the engine. Radiator fan started as soon as I turned on the key and runs constantly.

My Haynes manual has been no help, and does not contain an a/c or cooling system wiring diagram. So I did a bunch of searches with no really helpful results other than operation of the radiator fan is somehow related to the pressure switch near the receiver/dryer.

I thinking that there must be an open circuit caused by one of the a/c connectors that I disconnected. Could it be the one at the pressure switch near the receiver/dryer? There hasn't been any pressure in that line to the receiver for years, and when I disconnected there wasn't even any oil in the receiver/dryer..........or the compressor or the condenser for that matter.... I mean the whole system was bone dry.

I saved that pressure switch and was thinking of just re-connecting the switch to the connector to see if it completes a circuit and shuts the radiator fan off.

But before I make any bold moves I thought I should seek your opinion.

Peter

Could be the pressure switch - though if the system was as empty as you mentioned, it should have kicked on constantly before as well. Definitely on the right track for it being open or shorted somewhere. Like the newer Corollas, there is a fail-safe feature that always has the fans kick on in the event of a electrical fault.

Most likely, the trouble areas are the radiator fan switch or the fan relay - both of these should be indicated in the Haynes manual, I don't remember where these are at off the top of my head. I'd also look for broken or otherwise damaged wiring, as those will mimic a failed open switch.

Thanks Fish for your reply.

Today I reconnected the pressure switch, and ,bingo, the fan went off. So I cut the switch off the receiver/dryer pipe and zip-tied it to the horn mount. Everything with the radiator fan is now back to normal.....it comes on when the temp calls for it and goes off when the temp cools down.

That switch is obviously an integral part of not only the a/c system, but also the cooling system.

Thanks again,

Peter

if you'd prefer, just jumper the switch or cut the wires and connect both together.