I am trying to put the AC back into my 1990 RS. I've done a bit of reading but I just want to make sure I have it right.I recently got a used hard line for the AC there is a high pressure switch on the line and I have a high pressure switch mounted on the back of the compressor. From what I have read I don't need the switch on the hard line if I have a single fan. There is a pigtail for the switch on the hard line in the wiring running along side the line but it doesn't quite fit. There is a tab sticking out of the switch which should fit a slot on the pigtail but the slot on the pigtail does not quite match up with this tab. If I match them up the two prongs in the switch do not line up with the two holes on the pigtail. I guess I just need to know if I need this switch. If so are there different versions. The hard line was pre 1988 and my car is a 1990. Any help would be appreciated.

 

I would think as long as you have one switch hooked up (compressor) you should be fine, You do have the low side switch hooked up on the receiver dryer right ?

 

Thanks for the reply. Yes I have the low side connected. There is just one connection not made which is the one mentioned in my previous post.

 

Give it a try and see how it goes, The fan(s) aren't wired into the pressure switches but with the compressor clutch. When the AC is turned on (clutch engaged) the fan(s) come on.....

 

I'll give it a shot.

 

Seems to me like my 89 uses the line switch to kick on the fans on pressure?

 

Depends on the car.

AFAIK the single-fan cars don't have that but I don't know all possible variations in all possible years, especially the 6-cyl cars (which I have never even looked at one under the hood).

The switch in the back of the compressor is just a high-pressure cutoff. Safety only, nothing to do with the fan.

For cars that had the switch in the line, all it does is, make the fan come on as soon as the pressure reaches a value that says it's in operation. Not strictly necessary in most cases although it does help the AC to begin cooling more effectively quicker right after turning it on.

 

To add to sofa, for ecm controlled fans, it goes to the ecm fan request. 87-older, the switch was closed and opened @ pressure, removing a/c and not grounding color wire causes the fan to run at key on, and run.88+ was reverse. TBI cars, it is a redundant ground to the hvac controls grounding the relay.