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Wondering if I can get some opinions on why my AC isn't blowing cold air. I had it in the shop last week for the AC R-134a conversion and the ac worked for about an hour. A few things I have checked already:
Purchased Arctic Freeze Dye and UV light. When I connected to the L pressure valve the reading was in the red which means "compressor off" according to the instructions
Used the UV light and only saw some trace amounts of yellow near L pressure valve so seems like the shop did do a dye test. No other signs of leaking along the L pressure line, H pressure line, evap or compressor.
Used a multi-meter to check the Ohms at the terminals on the AC clutch which read 4.6
AC Clutch seems to engage when power is turned on. See video:
Thanks for the quick reply Interpon and the questions. Answers are as follows:
#1: I am new to the Corvette world and this was the first time I used the shop. Wasn't thrilled with their attention to detail on a few other things they did so I am not inclined to bring it back to them. Since the AC worked when I got the car back and there do not appear to be any leaks, seems like I would end up paying for a new compressor or clutch so might want to take it somewhere else or tackle it myself.
#2: AC was not working before. Kinda of thought I had to switch over to R-134a but apparently not. Again, would have been nice if the shop gave me some options.
#3: I have not tested voltage at the clutch yet. Need to figure out how to do that
Check voltage in pic..12v on clutch on if system is on and no failures of pressure or freezing..off should freewheel...verify but keep hands away...you can also put 12v directly and short test it...
i see your ground is spliced too..
take and add a few pics...
also what pressure did you get? Show poc of fittings too...if converted they shouldhave installed different valves and label as converted...if r12 before they should have flushed and changed oil accumulator and orifice at a minimum...
Very helpful posts. Below are a few pics. Doesn't look like much was done except adding the valves. I do not think orifice was replaced. I can pick up a reman R4 compressor/clutch for around $175. Wonder if that might be the quickest way to get this working?
You need ac gauges to see if it's undercharged and what pressure can the compressor generate. The clutch is engaging the compressor, Can the compressor generate pressure, How many miles on this?
Last edited by Mrvettenick; May 23, 2021 at 06:53 PM.
Ok...before throwing money at it...
Let’s make sure yoir clutch is getting full 12v as mentioned before..it should freewheel and not move if no voltage.
if it drags at no voltage then clutch bugared.
so if you want to diy...which I recommend...
then here is your required list of tools
Manifold gauges for 134... you may be able to rent from auto stores...look around..this is required regardless of direction you go.
vacuum pump...maybe can rent but they are handy...harbor freight or amazon..
compressor air to see if system holds pressure...
i like robinair brand..
good news is Walmart 134 cans cheap enough...
so what’s compressor doing?
how’s that wire spliced at the ground?
i do NOT like remanufactured r4 compressor..i would go new..they are not the most reliable..i went napa new and 3 year warranty...price point not that different.
if compressor bad then you will need new orifice, accumulator, flush system re-oil and charge..o rings and seals..
a very satisfying job..
Last edited by interpon; May 24, 2021 at 12:38 PM.
Before you start spending money on tools, especially if you never worked on ac systems, get an estimate to see exactly what the issue is. You can do more damage with the right tools, especially if you are not experienced in this area.
Check the connectors..the one for aux fan if it ever comes on is 25 amps..
is that a splice bypassing pressure switch? Others may know more..I don’t like it
The danger of jumping the low pressure switch is that the evaporator will freeze, from not cycling. AND, if the system is undercharged, then compressor damage will occur,;
You better find another shop that knows what they're doing.
You need ac gauges to see if it's undercharged and what pressure can the compressor generate. The clutch is engaging the compressor, Can the compressor generate pressure, How many miles on this?
To me the LT.GRN wire (Circuit 66C) and the LT.BLU wire (Circuit 67) are tied together using the Blue ScotchLok connector.
This is bypassing the Low Pressure Cutout Switch sending voltage directly to the Compressor Control Switch.
If you follow the LT.BLU wire (Circuit 67) it should go to the Compressor Control Switch (or Thermostatic Switch).
The other wire at the Comp Control Switch is DK.GRN (Circuit 59) that goes directly to your compressor.
The porpoise of the Thermostatic Switch is it cycles the compressor on/off.
If the temp drops below 33* at the Thermostatic Switch the switch opens stopping compressor.
This helps prevent Ice buildup on the evaporator coils.
On the drawing at the Lt.BLU LT.GRN box is where the Scotchlok is at.
Like I said, follow the LT.BLU wire going to Comp Control Switch, it may also be tied together with a ScotchLok.
If so, that would keep the compressor running all the time and NOT cycle on/off like it should.
Or the Compressor is simply not getting the CCS cold enough to open.
Last edited by bmotojoe; May 23, 2021 at 09:35 PM.
so first get a can or 2 of r134 and a charge hose with gauge. snap the gauge on and read the pressure in the system when engine not running. i bet it is too low. next, add some r134 until pressure shows correct. now you have cold air. when the refrigerant runs back out the leak, it will stop making cold air again. that gauge only reads low side, but you can get a good idea if system works by seeing it drop when compressor starts.
so first get a can or 2 of r134 and a charge hose with gauge. snap the gauge on and read the pressure in the system when engine not running. i bet it is too low. next, add some r134 until pressure shows correct. now you have cold air. when the refrigerant runs back out the leak, it will stop making cold air again. that gauge only reads low side, but you can get a good idea if system works by seeing it drop when compressor starts.
i agree.. but really want to know WTH is going on with that clutch first with and without proper voltage (op you measured ohms.. that same meter should do 12v DC) .. non starter to me..open system if bad.. ground zero flush inspection , proper OIL and amount.. if that pressure switch is bypassed and refrigerant low it will not carry the oil, even if it has the right oil and amount..
From: At my Bar drinking and wrenching in Lafayette Colorado
It's absolutely not possible to troubleshoot or diagnose an air conditioning system without proper gauges hooked up (both high and low sides). It's not possible to repair an air conditioning system without a vacuum pump and a way to pressurize and leak check. If the OP does not have the correct tools for the job, he needs to pony up and take the car to a qualified A/C shop for proper diagnosis and repair. Discussion about what the problem "might be" without gauge readings is completely pointless.
(Most common cause of "A/C worked, and now doesn't" is leaks.)
Lars
Former Vapor Cycle Air Conditioning Systems Instructor
Parker-Hannifin Airborne Div.
Yep, I fully agree with you, not wanting to take it back to the shop that did the changeover. I’ve been there before; having work from others fail prematurely.
The refrigerant circuit is more sophisticated than most think. It is a balancing act. If the 134A circuit is not charged properly, or if any of the internal components such as the expansion valve, the dryer, etc, are not working well, the system will not cool. This stuff is not as forgiving as R12. You need good tools and training to diagnose this problem.
My gut feeling, a failure in the refrigeration circuit. Have a good qualified Auto AC guy check it out.
AC Problem Diagnosis Help - Not Blowing Cold Air
