A/C pump on and off

[Novasmithjohn]

I just replaced the a/c pump on my 99 Tahoe. Used 8 oz pag150 and 2lb 134a the pump cycles on and off until the engine start to get warm then it will not stop running. Is there a sensor that is going bad and causing the pump to stop running?

 

[exp500]

Switch position matters, compressor runs on defrost also. So... More info needed. What are your Pressures/ Temps after charging system?

 

[Eman85]

System is CCOT, clutch cycling orifice tube. It cycles the clutch to control the flow of freon and the clutch is controlled by the pressure switch at the accumulator. Did you follow all directions and replace the accumulator and orifice tube along with flushing the system? Are you monitoring pressures when the clutch cycles?

 

[Novasmithjohn]

When the compressor runs the pressure is 25lb at 65 ambient air temp and 60 when the compressor is off on the low side. The air temp at the vent is 49. Changed the accumulator and oriface tube. New condenser and evaporator. Didn’t flush

 

[exp500]

Would be better if you had hi side pressures and humidity too. As a guess, I would say you are undercharged. 27-30# is kinda normal for 65 degrees.

 

[Novasmithjohn]

I’ll get another can and add it and see if it improves the operation of the system. Will post result. Thanks for the help

 

[Novasmithjohn]

got a nother can and put it in have a solid 30 lbs now but have to power the clutch off the battery i have power at the switch on the acumilator and at the the switch mouted ontop of the compressor, but there is no power at the switch on the back of the compressor. I dont have a deacent wire diagram for the a/c system only the one that in the haynes paperback. which is foe the trucks does anyone one have adigram that is for the Tahoe? Thanks

 

[Eman85]

Top of compressor is the clutch wires. Back of the compressor should be high pressure cutoff switch that provides ground. All of this from memory so it comes with a disclaimer.

 

[east302]

I dont have a deacent wire diagram for the a/c system only the one that in the haynes paperback. which is foe the trucks does anyone one have adigram that is for the Tahoe? Thanks

Here’s the diagram from 1999. The full manuals can be downloaded at the link below (see post #77):

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[Novasmithjohn]

Thanks for the information and the diagrams I replaced the high-pressure switch and have the other 2 on order. I’ll post what I find. went to get the downloads and it wanted me to download a game is that correct?