AC Issue

[Restrorob]

New to the board

Hey guys, I'm having a issue with the AC in my 97 GMC EXT Cab.

When I bought it some 9 yrs. ago the AC didn't work due to no refrigerant in the system, I pulled it down and charged it to leak test the system and everything worked fine and it blew cold. I found the evaporator was leaking, I never replaced it because I only drive it to car shows in the area.

Fast forward to now, I'm ready to rip the whole dash apart for the evaporator replacement. I jumped the high and low pressure switches to make sure everything was still working okey, I found the compressor clutch kicks in when I push the AC switch on the dash but then it kicks back off when I turn the blower switch on, as long as the fan switch is off the clutch stays engaged.

In all my years as a auto tech. I've never ran across something like this, any ideas where to start diagnosing ?

Thanks !

 

[GoToGuy]

Why did you jump the high pressure switch? It's normally closed until high pressure the opens to cutout the clutch.
If you have a completely empty system you can pressure check system for leaks with nitrogen ( perfect world ) or shop air, " Leak Check, soapy spray " . Just a thought.
Have looked in the service manual. In sticky above are links to download OE factory service manuals, your year.

 

[Restrorob]

Why did you jump the high pressure switch?

It was much easier to slide a paperclip into the connector than to try probing the tiny post up inside the switch with a multimeter to make sure it wasn't faulty and open.

Also, there is no 97 manual in the sticky and trying to download the 98 gave all kinds of pop-up crap and my Norton antivirus detected threats......

 

[PlayingWithTBI]

If you have a completely empty system you can pressure check system for leaks with nitrogen ( perfect world ) or shop air, " Leak Check, soapy spray " . Just a thought.

Nitrogen - yes, shop air - no. Unless you wanna change the filter/accumulator. There's usually too much moisture in compressed air. This is why your air compressor has a drain valve in the tank.

 

[df2x4]

Also, there is no 97 manual in the sticky

There are, you just didn't keep scrolling far enough. Other members have added missing manuals to that thread over time. The '97 manuals are on page 10, post number 92.

https://www.gmt400.com/threads/88-98-service-manuals.43575/post-1286309

Which specific links to the '98 manuals gave you trouble?

 

[Restrorob]

Which specific links to the '98 manuals gave you trouble?

Thanks for the link, in the first post I was able to download 98 volume 4 then went for volume 3 and it gave all the crap.....

 

[df2x4]

Thanks for the link, in the first post I was able to download 98 volume 4 then went for volume 3 and it gave all the crap.....

No problem!

That's strange... I just downloaded and opened the '98 manuals as a test, all four volumes are working fine on my end.

 

[Restrorob]

Just wanted to update this in case someone else has the same type issue, I threw a complete switch assembly at it and that solved all the issues.....

 

[GoToGuy]

The fan switch or a HVAC control panel assembly?