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A/C low side switch for R134a

3500GMC

3500GMC

What T F, over
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Or high side also?

I can almost keep a skinned chicken refrigerated properly hanging from the rearview... But.. the A/C clutch cycles off-on-off-on-off at higher revs...

Is there a switch specifically for R134a or is it snake oil?

My old refrigerant was R12 (?) and it's been kinda sorta retrofitted by me so far.. O rings, new receiver/drier and such.

Pressures different for R134a vs. R12?

'splain me please..
 
Hi

Is it the original AC system yo use, or is it replaced by a newer one.
Does it cycle on\of only at WOT, or mid range to??.
Have you connected manometers to the system to watch the hi, and lo side pressure when idle.
If charged with to much R134 it can cut the compressor for safety.


Børge
 
Original parts except for receiver/drier, new orings and R134a.

Worked great last summer, now the compressor cycles off- on. Maybe I need to get it hooked up to the gauges and add refrigerant.

Will begin cycling off-on around 1500 rpm now.

Somewhere I read there was a different system switch to use when doing a refrigerant 'retro-fit'. Maybe I misunderstood it, I dunno.
 
It could be a good idea to recharge it just to be sure ot is the correct amount of refrigerant.
If you have to little refrigerant it will also shut the ac system off.
 
Mine cycles as you described when low. When I add refrigerant it stops. I need to find my very slow leak!
 
Check your pressures, but the R-12 switch should work fine if you have your oil charge close. I believe the R-134 switch is an 18-20 PSI cut-off where the R-12 was a 15-20, so basically the same. I believe they both kick back in around 50-55. If your still using an R-12 condenser that won't be helping you any at an idle or low speeds.
 
Thanks guys. Thank you Børge for the pictorials too.

Yeah the condenser is still the OEM jobby AFAIK.. So I guess I'll take the hit on a less cool idle temp.

The system was 're-oringed' with the green orings. Did a new comp manifold seal too. System was drawn down and filled last summer. I remember using 1 8oz can of oil charge and plain R134a with no other 'stuff'...

Perhaps now I have a leak. I think it's the low side switch leaking.

Maybe I can add a can of refrigerant with dye and check it out then...

In review, if everything is where it needs to be, the *R12* switches are not a factor, right?
 
What kind of oil charge did you put in it? Did you flush it out with an A/C system flush when you had it apart? If you mix mineral oil(R-12 used a mineral oil) and PAG(R-134 normally uses PAG), you get a NASTY mess inside the A/C system that will plug it up in short order. If you used an ESTER oil you should be alright, except that your probably over charged on oil(a full system charge for a dry system is about 6-8 ounces). ESTER oil will mix with mineral or PAG, but NEVER mix mineral and pag in any way.
 
Oh man I can't remember back that far.. :hihi:

But, no flush.. just replaced the rec/dryer. Could now have a real mess on my hands. :eek:

If I could start over, recommend a flush and fill procedure... It could very well have too much oil now.
 
I would start over by pulling the compressor off and draining it, replace the drier, and check the orifice tube screen for debris. If you mix PAZG and mineral oil it will make like a black tar that will plug the screen on the orifice tube. Flush it out and start over with a fresh ester oil charge of about 6 onces. Charge it to about 75-80% of the rated R-12 capacity and see what the pressures are. Also a variable orifice tube works really good for conversion systems.
 
Can we take a chance and use the existing cores? As in- 'most' of the oil will be in the dryer and compressor, right?
 
3500GMC said:
Can we take a chance and use the existing cores? As in- 'most' of the oil will be in the dryer and compressor, right?
Click to expand...

Flush em out good with a low evaporation point flush and compressed air, then pull a vacuum on it for 30 minutes and call it good as far as the cores go. I would replace the drier as they don't cost that much, and are pretty much impossible to flush out completely.
 
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