1989karr

Anyone else have this issue? Car is a 87 305 TPI



I changed the a/c pressure switch in the ac pipe that controls the fan when the ac is on. With the switch disconnected, the fan constantly runs. Changed the pressure sensor in the compressor too.

But when I connect it...SOMETIMES it will come on, but most of the time the fan stays off with the ac on and the pressure and what not gets high! Fan works fine when coolant reaches operating temp so I know it works. Its just when the ac is on that it doesn't go on? Anything else contro lthe ac fan aside from the switch in the ac pipe?

LiquidBlue

not sure about an 87. is it one or 2 fans? if the switch is disconnected, sounds like it is setup to be fail safe if the switch goes open. which if I recall, that is not how a 90 w/ 2 fans works. there are some fan diagrams around this board. search for 1987 cooling fan diagram thirdgen.org


http://austinthirdgen.org/mkportal/m...ine_wiring.gif

LiquidBlue

based on that diagram, if that is what you have, it looks like ECM is in total control of the fan.

1989karr

It's a single fan. I installed dual fans and hooked up the second separately but the original fan still doesn't come on.



I tried replacing the ECM and PROM with another unit I have...same thing!

Could it be a grounding issue? Any idea where the fan grounds with the ac?

LiquidBlue

can you clarify a little better which fan is behaving which way. I'm a bit confused on the exact issue.

1989karr

Sorry about that, I added dual fans (they were free!!) but the second fan is run off a separate wiring unrelated to the stock one.

So the fan connected to the stock single fan harness is the one not working. When it was a single fan it didn't work properly either so it's not something I did while installing the dual fans 9they are not tied together in anyway).

So the original wiring for the single fan is giving the problem.

LiquidBlue

If you say it is intermittent, then it could be a loose wire, or poor connection. find the ground wire, and measure resistance between it and ground. also measure resistance between the fan connectors and the fan relay. and make sure your relay is operational as intended. that is where I would start.

1989karr

Any idea where it grounds for the AC signal? I replaced the cooling fan relay, that works fine as well.


it works great for when it reaches operating temp, so at least that part works....its just the ac when it doesn't work.....but I don't know where the ECM / how the ECM grounds it etc...

LiquidBlue

the fans should be independent, so debug one, then debug the other.. did you try to wire them together, don't understand what you question is? the primary should only turn on at a certain temp. both will turn on when the a/c is turned on in a factory 2 fan setup

LiquidBlue

another thing to examine for fan 1 is temp sensor, it will tell ecm when to turn on primary fan. i feel your pain, I'm having troubles figuring out why a 1999 Toyota Solara both fans always running.. trust me, our systems are easier. you are in luck!

1989karr

haha i have a camry, same era! Did you check the ac pressure switch?
For mythirdgen, I guess to clarify, the second fan is run off a diff circuit i installed myself, and is independent from the cars electrical system. so its not attached to the factory harness at all. The first fan though is a direct plug in from the stock single fan / its the same motor. So theres some kind of fault in the wiring somewhere..ugh just cant find where!

LiquidBlue

well, I would do what I suggested earlier, and start with the primary. as long as the original was working before the swap, sounds like a wiring issue. once you get that figured out, at least you can drive the car.

1989karr

almost a year later...I think the connector at the relay was UGLY like the wires were kinda exposed...I put some electric tape and it seems to be working fine now...i think there was a short or something...i ordered a new connector from hawks!