1991 ZR-1, New Compressor, Condenser, Evaporator, Accumulator, Variable orifice tube.

I installed an in-line filter on the high side.

I added the amounts of mineral oil recommended in the factory service manual (I think it was 3oz in evap, 1oz in condenser, 2.5oz in accumulator. Compressor had about 3.5 oz).

Pulled a vacuum on the system, held overnight with no leaks.

Charged with 36 ounces of R-12 (3 x 12 oz cans), factory spec is 2.25 lbs = 36 ounces.

Now, the compressor runs, and the suction line gets cold, and develops condensation, but the evaporator just never gets as cold as the suction line. Vent temps are barely cooler than ambient temp.

I have a set of gauges, the low side cycles down to about 28 with comp running, then cycles off, and goes up to 50 or so.

I still have to pick up a high side adapter, so admittedly I don't know what the high side is doing.

If I jumper the low pressure switch coming out of the evap, the compressor stays on, the accumulator and low side pipe frosts over, but the evaporator doesn't seem to get much cooler.

I removed the jumper, plugged the switch back in, compressor goes back to cycling every 4-5 seconds, then after a few cycles, I get a code 09, indicating low freon. I know I put 36 ounces into the system. Any ideas? The FSM is confusing to me in this area.

 

Sounds like your short cycling from low freon - I bet you have at least 1 leak.

A system can hold a vacuum but actually "leak" once freon (positive pressure) is introduced into the system - which is pretty frustrating. There are simple dye leak detection kits (black lights) available that will help you narrow down your leak (s) search.

I understand this is a "Z" and you may be wanting to stick with the 12 but this would be an ideal time for changing over to 134a.

Tips:

Get a set of gauges (12/134a) that does both the high and low sides.

Depending on your level of experienece - if your unsure of how much freon is actually still in the system evacuate/recover (since it is 12)the system and start over.

If you reused the old hoses/ threaded fittings - the threads on those fittings tend to get buggered up (example: aluminum slivers/pieces from the old dryer/accumulator often get embeded into the hose fitting's threads) and can make a fitting feel "tight/snug" when it is really not. Adding a few drops of mineral oil will help ease the level effort needed to retighten damaged threaded fittings. A couple of huge (1.5 to 2' long) wrenches will also help a ton....leverage.

Remember - with the system running portions of the system will get colder/hotter than what they were when they were installed/tightened....expansion/contraction....sometimes leaks only appear at these times.

It is a good idea to "run" an AC system until it gets up/down to operating temp then retighten any and all fittings that were loosened.


Additionally, if you have condensation at/on the dryer/hoses then the evaporator should be "cold" as well......you may want to check to see if your "blend" door is shut....sounds like it is partially "open" and mixing heater core air (hot) and AC air (cold) and only producing "Vent temps that are barely cooler than ambient temp".

 

I appreciate the input. I am not interested in converting the system to R134, the ZR-1 was equipped with an undersized compressor to begin with, and I am not interested in degrading the system's performance any further.

After I evacuated the system, I put only one can of R12 in, and let it sit for 24 hours, and there was no significant pressure drop (other than temperature-related fluctuations).

I already disassembled the heater box, and observed the blend door swinging open and closed depending on the requested temperature. There does not appear to be a problem in that area.

I have a nice set of hi/low gauges, but I'm waiting for the hi side adapter to arrive before I can check the high side pressures.

 

The only explanation is a plugged up Evaporator - assuming of course the Temp Door is blocking all the heat. Given the pressure - allmost textbook at 70 degrees after you dumped 3 cans in it, it's not internal, but the inlet foam filter that was glued on from the Factory. You can't see it without splitting the case and that filter usually falls apart and then collects all sort of debris, when the Evaporator leaks. I'd go to a shop and ask them to stick an Electronic Leak Detector in the Center Vent. If it goes off, the Evaporator is leaking. Something appears to be leaking given that it's now acting as if the charge is low and of course you can't see an Evaporator Leak, though they often spit little oily ***** of foam out of the vents once the filter falls apart (or see if there's any greasy stuff on the windshield).

 

Opps - just noticed you replaced the Evaporator??? If so, the temp door, given the low side, isn't working, and you still seem to have a leak. No other explanation when the Low hits 28 psi - that's about 36 degrees with super heat of 8 degrees - 42 to 45 should be coming out of the vent.

 

I agree that the symptoms seem to fit with a plugged evaporator since only part of it seems to be cooling - however, it was a brand-new (aftermarket) evaporator, and it did seem as though the system was sealed up tightly. My next step IS pretty much to have a shop look at it, since I can't recover the R12 myself, and I'm reaching my frustrating point rapidly on this issue.

on some AC forums, the variable orifice tubes are frowned upon - and I'm wondering if that could be the source of my problem here.

Thanks
Andrew

 

Given the Low Side, it isn't the orifice, though I don't have any faith in those variable doodads. If you want variable, swap out the Nippo compressor for a GM variable stroke model and ditch the low pressure switch (which is what GM has done since the C5) and keep the fixed orifice. You could put your thermometer next to the Evaporater - remove the Blower Module - and see what the temp is. Also check to see that the case is sealed to the firewall particularly at the bottom - jack it up and put your hand underneath it to make sure all of your cool air isn't being blown onto the pavement.

 

Yesterday I removed the blower resistor module, and felt the evap. The forward few cm get as cold as the suction line leaving the evap, but the rest stays lukewarm at best. Almost as if there IS a blockage in the evap.

Thanks for your help.

 

Because I've got no way to recover and weigh the R-12, I'm going to bring it to a shop tomorrow for diagnosis and possibly R-12 recovery if needed. The rapid cycling, and code 09, would point to a low charge, even though it's been doing this right from the first moment I added the full correct weight, I think I'm just a little over my head here.

 

Don't kill that new compressor those things ain't cheap. Keep us posted with what you find as the issue.

 

Yah, don't want to kill that new compressor, that's for sure... hopefully I didn't already cause any damage to it. I'll post up with what I find out tomorrow.

 

Compressor should be fine as long as it's got the right oil charge.

Something isn't allowing air to flow over the majority of the coil.

 

If it was just air flow, then the coil should still feel cold to the touch, through the hold for the blower resistor module. It sounds more like evaporated refrigerant is not flowing through most of the coil.

 

Follow-up:

Had the system evac'd today. Changed out the orifice tube for a standard one. No change. Evac'd again, went home to take out the evaporator, found over 8 ounces of oil in it, instead of the 3 that I know I put in. So, where did the oil come from? Is my accumulator and compressor now dry? What would cause the oil to all end up in the evaporator?

 

COmpressor had less than a half oz. of oil in it, looks like all of the oil in the system ended up in the evap. WTF would cause that?

 

I know you said you used mineral oil.... Ester oil? There are r12 and 134a blends...you have to hunt for the right stuff on the internet for true r12. Its just a thought

 

Straight mineral oil, 500 viscosity, as per the recommendations for an unconverted R12 system.

 

In this application, with the freon as the transport, it is pretty normal for oil to move through the system. If you only put 3oz in the system and now you've discovered a total of 9oz then some of that oil was in there already and this may have been part of the problem. Before you installed it- did you check/drain out any oil that may have already been in the compressor or other components when they were purchased?

If it were me, since the system is currently "empty" I'd be tempted remove the components and drain/clean them of any and all oil or for the blockage your suspecting and then start over with the installation. Get more oil and another "o" ring gasket kit if needed, clean all the reused threaded hose fittings. Reload the system components with the correct amount of mineral oil. Dip the "o" rings in the mineral oil just before installing them. Put a small amount of mineral oil on the threads of each of the fittings before you attempt to tighten them. Use some longer wrenches to really "tighten" up the fittings/orings seals on the components. Pull a vacuum - let it sit for a bit - if it holds move on to charging the system.

 

Thanks for the advice - not sure if you saw my other thread - I cut the evap in half last night, and found that 90% of the plates coming up from the inlet end are not flowing much of anything. Not sure why, but it is definitely obstructed.

 

I didn't see the other thread. Sounds like your all fixed then. Get a new part(s) and put that thing back together quick it is getting hot out there....this week we already got record high temps, for this time of year, here in Tampa.