I've been debugging a cooling fan problem and I'm trying to locate the AC pressure switch, is it one of the switches in the compressor itself or in the line? A pic would be great. The car is a 91 Z28 305 TPI with dual fans. The issue is the secondary fan is constantly running. I've already replaced the relays (both just to be sure), fan switch & new connector (from TPI parts).

Thanks

 

theres a two-pronged pig tail connected to the switch just before the freon canister.

atleast it is on mine. (low pressure switch, that is)

hope it helps...

 

Look at Autozone.com. They have a set of very good "Vehicle Repair guides", and as part of it they have complete wiring diagrams for our cars. You'll need to tell the website what kind of car you have, then hit "Repair Info", then "Vehicle Repair guide", then "chassis Electrical", then "wiring diagrams". THen find your car. They have Body diagrams and engine diagrams. Look at them all. It will surely help you solve your fan problem.

There are 2 pressure switches on our cars stock a/c systems. One is on the accumulator (freon canister as pur3d said), its the grey tower looking deal on the passenger side of the engine compartment. It should have a few valves and some lines sticking off of it. Your looking for a black rubbery connector that when removed looks almost like a wall outlet. You'll have 2 prongs sticking out of the accumulator. Those prongs are the switch itself. Its a normally closed switch that opens when the pressure on the low side of the system is too low. Technically its called a "pressure cycling switch" and in normal A/C operation will cycle on and off periodically.

The high pressure switch is located on the backside of the compressor, towards the top. Its a round plastic connector when removed has 2 small pin style female connectors, to accept the 2 male pin connectors from the switch. The high pressure switch is also normally closed. It opens when the pressure is too high, I don't believe this switch normally actuates in operation, I think its a safety thing.

Both of these switches are strictly to cut off the power to the A/C compressor clutch and disengage the A/C compressor. I don't believe they have anything at all to do with the secondary fan in your car.

 

bobdole369 thanks for the reply, the Autozone site is pretty cool. Actually the TPI cars (I can only speak for the later ones) with AC came, with dual electric fans. The secondary fan is turned on by 1) fan switch between #6 & #8 spark plug 2) AC pressure switch. I found the AC pressure switch that controls the fans, its actually in the line, on passenger side, right near the wheel well. Following the tubing from the front of the car on back. There is mention of it in the wiring diagrams, but not the location.

Thanks,

 

Check this link:

https://www.thirdgen.org/forums/atta...g?d=1121439309

Here's the rest of the link:

https://www.thirdgen.org/forums/faq-...electrics.html

JamesC

 

JamesC, great info thanks. Nice pics too.