Automotive Air Conditioning Information Forum (Archives)

cycleslim on Sat November 05, 2011 5:41 PM

Year: 1997
Make: Chev
Model: K1500
Engine Size: 5.7
Refrigerant Type: R134a
Ambient Temp: 50
Pressure Low: 20
Pressure High: 160
Country of Origin: United States

I just installed a complete system (all new components) in my '97 K1500 with a 5.7L - just in time for a Minnesota winter - I know
I used all oem parts except for the evap (Four Seasons) and the condenser (Spectra Premium), Delphi pump.

Did all the correct procedures before start up I think thanks to this site.

vac down the system for an hour
let sit for an hour -
no leaks
charged the system with 2 lbs (just shy) of R134a measured out with digital scale
getting plenty of cold air - 38 degrees


The problem is now the system keeps cycling on and off and I don't know why.
I should mention that it does not cycle with the hood down - stumped on that one - or is this normal

I had to jumper the low pressure switch to get the first can in the system.

also when the pump first engaged it was extremely quiet- now has a definite "noise" to it

and when I disconnected the high side gauge hose noticed the oil was a very dark (hopefully not black) color.

the orfice tube fit a lot looser in the after market condenser than the original - could this affect operation?

any ideas?

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I know just enough to be a danger to myself

mk378 on Sat November 05, 2011 7:26 PM

That is what a cycling compressor system does. It cycles more in cool weather.

Noisy compressor and black oil is not good. Did you drain and replace the oil that may have come with the new compressor? Do you know the amount of oil is correct?

Edited: Sat November 05, 2011 at 7:27 PM by mk378

cycleslim on Sat November 05, 2011 8:15 PM

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I know just enough to be a danger to myself

cycleslim on Sat November 05, 2011 8:22 PM

I did drain and measure the oil that the comp. came with but I put it back in.
measuring 6 oz for the comp.

I had a new bottle of PAG 150 and added 2 oz to the accum for a total of 8 oz for the system.
Is this correct?
should you always replace the oil that the comp. was shipped with?




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I know just enough to be a danger to myself

70monte on Tue November 08, 2011 8:27 PM

I completely redid the systems on both of my 98 chevy trucks and did not have any of the issues you experienced. I replaced everything on both trucks except for the line from the condensor to the evap.

You should not have had to jump the low pressure switch if the system was vacuumed down correctly. I didn't have to on either of my trucks or on the 99 Suburban I had to recharge twice. Did you vacuum with both sides open.?

If the OT was loose in the line, it is possible that refrigerant is getting around the OT as well as through it. You have good vent temps but of course the outside temps are low as well. Are you sure it was pushed in the line all the way?

I always replace the oil in the compressor with new oil and even though the new compressor had 6oz's in it, that sounds like too much to have in the compressor alone when the entire system holds 8oz's. I always put a max of 4oz's in the compressor with the rest in the other components of the system.

If the oil is already dark, then you have a problem. It should not be darker than what you put in that quickly and if the compressor is making noise already, it has an issue. I would pull the OT again and see if you have any debris on it and that will determine what you need to do.

I have read that the outside temps should at least be in the high 70's to accurately charge an AC system but I don't know for sure.

Wayne