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More weirdness, so bought the car and was told AC did not work, looking it over found the + wire to the compressor unplugged from the harness. So when I plugged it in the left rad fan came on, now the car was off and the compressor clutch did not lock. The only way to turn the fan off was to unplug the +compressor wire! Sent the AC control box to get overhauled, also a mechanic brought his AC gauges over and hooked up, we ran a hot wire to the compressor wire and the engine running the compressor worked. He said it looked like the system was out of Freon. So put the overhauled AC controller in yesterday and with the car off when I plugged the compressor wire into the harness the fan came on, I cranked the car turned on the AC and the compressor did not engage.
Studying the “Ventilation,Heating, AC” schematic and noted the “bonnet contact” switch sends info to the “coolant fan and flap unit” well on my car it is broken and “open” all the time (see photo ) so just hooked up the compressor, car off, and left fan comes on but when I jumped the bonnet contacts and “closed” the switch the fan cut off.
So this switch has something to do with the fans, I guess next I need to make a jumper wire and crank the car and see if it will let the compressor work?
any info on a new switch?
Dan
Many mysteries regarding that switch.
I have searched and read a lot about it.
(still confused)
(I have no right fan with a/c button pressed)
Supposedly with hood open it cuts off the fans to prevent injury.
Some say that is when the engine is off and the fans are still running.
I am interested in bypassing that switch completely.
Would that be connecting the 2 wires or leaving them unconnected?
Well mine has been open until just now, and closing it turns the fan off. Now again this is with the compressor disconnected, so now I have the wires connected closing the contact and put some heat shrink over it. That will do until I get a new switch. Cranked the car and the left fan runs but not the right(car is cold), turned on the AC but the compressor is still not turning on, but I have read the if the system is really low on Freon that will also keep the compressor from turning on.
so grounding that switch just grounds a circuit in the cooling fan unit.
You can supply 12v and a ground directly to the fan that isn’t coming on (if you haven’t already) to test to see if it even works at all. The fans don’t last forever.
Yes you are correct there is a pressure switch (on the '86 it's on the drier) that will not allow the compressor to run if it is low on refrigerant. There is also a freeze switch inline under the cowl covering; those can burn out. They are not expensive to replace but one way to test is to bypass by connecting wires together and see if it makes a difference.
You could bypass the pressure switch but if the freeze switch isn't working the comp. won't turn on.
This seems to be the opposite in my car with the my wires open the fan runs but when I connected the two ends the fan is off. Could it be a normally open switch and when you open the hood it closes? Hard to tell from the book.
You aren’t saying whether or not the car is running or if the key is on.
If the car is running and up to operating temperature both fans should be running, regardless of hood up or down. If you then shut it off, with the hood closed, the fans may keep running for awhile; but in that case if you then open the hood they will shut off. Hope you follow.
The only time I can remember seeing just one of my fans running was when one fan just wore out and died. Replaced both 23 year old fans.
OK, here is the car I have tested it with the engine on, AC on, but the engine is not at running temp (it’s hot here!) have just tested the violet wires at the icing switch, no volts with engine running AC on. So the flow list says issues are with the switch and I am trying to find the four wire plug with a violet/white wire to check.
my hood plug is wired closed at this time so the car thinks the hood is closed, I think.
Just ran the car so the temp was normal, the right fan was not on so I pushed it with a stick and it spooled up. Watched it a few minutes and it did appear to be slower than the left. So will replace them. I am sure they were both running the last few times I was working on the motor.
So still trying to work from the compressor back, I have a jumper on the low pressure switch and the plug from the compressor to the harness is plugged in. So from what I can tell from the schematic is the single wire off the freeze switch should send power to the compressor. Also I have ohm’ed the freeze switch and it shows no resistance through the switch, and that seems correct since the evaporators are warm.
So can anyone confirm that the single wire off the freeze switch goes to the compressor through the low pressure switch?
Pushing the AC button closes a relay on the control head board which sends power to the freeze switch. From the freeze switch power goes into the CE panel* and out to the hi/lo pressure switch then to the compressor clutch.
(I want to put in a relay to both independently power the compressor and an additional fan. Best place to do this appears to be at the hi/lo switch.)
08-08-2021, 11:37 AM
A/C and rad fan
