R4 compressor NEVER cycles

[eb4tx]

I have a 1995 Suburban in excellent condition. A/c system cools well BUT, the compressor clutch never cycles. I mean NEVER. Driving around under 30 minutes I can see 40 degrees out of dash vents on a 90 degree day. But, on a longer drive I believe the front evaporator starts to ice up. I will start to have condensation on the inside case. I have changed the pressure switch on the accumulator and the pressure switch on the condenser. Both ACDelco OEM switches. I have had the system evacuated twice in the last year just to make sure the amount of R134a was correct. Both times system levels were spot on correct. My situation is I live an hour drive from any nearby town. I have been to several a/c shops and with no solutions. I'm a pretty handy mechanically, just don't have any a/c gauges or tools. I guess I shouldn't complain as system does cool well, but knowing the clutch should cycle and it doesn't has me very concerned. Any thoughts on why the clutch NEVER cycles?

[Dougflas]

need to know ambient temp. if it is hot enough, the compressor will not cycle due to heat load. low airflow may cause evap to freeze. tape manifold to windshield and indicate pressures. without checking system, you may have a defective cap tube switch in the evap or it may not be in proper location.

[Cusser]

I don't have my 1988 or 1994 Suburbans any longer that had R4 compressors, but I'm not positive that these systems were made to cycle; like maybe running full time and one would just blend in some heat if the vent temperatures were too cold.

If you're in a humid-enough climate, wouldn't you notice evaporator freeze up by decreased VOLUME of air coming out the vents?

And couldn't you switch the compressor OFF manually with a dash switch like for a minute every 10 minutes to allow any ice to melt and drain out the condensate tube? Let's assume that the condensate drain is not clogged.

[JohnHere]

I'm wondering, though, whether the evaporator is actually freezing up. When you think it is, do you also notice a marked reduction in airflow from the vents along with a change in sound from the blower?

[eb4tx]

First off, I live in Central Texas, it's end of May and it's 90 degrees by 11am. This is the description that GM states for a 1995 Suburban: "The A/C system is a Cycling Clutch Orifice Tube (CCOT) type with a fixed displacement compressor and pressure cycling switch to control evaporator temperature". So yeah, its suppose to cycle. As for as the evap freezing up, just a guess as interior a/c case starts to sweat and drip. Also the drain tube flows like a river outside via the drain tube. Drain tube is NOT clogged.

[eb4tx]

Photo of 1995 Suburban. 145k miles. I'm the second owner.

IMG_0694.jpeg (137.37 KiB) Viewed 8695 times

[bohica2xo]

If you pull the connector off of the cycling switch, does the compressor stop?

[eb4tx]

@bohica2xo. " If you pull the connector off of the cycling switch, does the compressor stop?" Yes it does. Plug connector back in, clutch engages compressor.

[bohica2xo]

So it can cycle, you just never get enough liquid built up in the accumulator to drop the pressure.

GM used an insulator for the accumulator on some models. Part number 15-10614

Might give that a try.

[eb4tx]

When I acquired this vehicle 4 years ago, it had the original foam fitted cover on the accumulator. The a/c worked fine when I got it, except I noticed the clutch never cycled then as well. That original R4 eventually developed a leak 2 yrs later and had to be replaced. Replaced compressor, and accumulator together at the same time. That original cover had deteriorated and was not in great shape so it was not put back on. So the issue of no cycling was present for 2 yrs with accumulator cover and now without the cover. I appreciate your suggestions hopefully we can sort this issue that has dogged me for 4yrs.