Advice - Compressor Not Engaging

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jpstewart19

jpstewart19

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So in an effort to get my factory AC running again (only have the car <1y), I recently replaced a cracked condenser, replaced the oil w/ester, relevant seals along the way, dryer, and expansion valve.

The Issue:
Pulled a tight vacuum over 6 hours with no leaks. When turning to max ac, rpm drops about 50rpm, but the compressor does nothing. No clicks...completely silent.

Do you think it could be a compressor or electrical/switch issue? I tested the lead to the compressor and got zero volts, but not sure what I should get.

Just hoping for some other thoughts / ideas on where to troubleshoot next.
 
If the rpm drops and the clutch doesn't engage it sounds like you have a electrical short to ground dragging the alternator down.
 
The RPM might be the load caused by the blower motor, or maybe something is froze up/ dragging. Jumper 12V direct to the compressor wire and see if it "SNAP" engages. You have enough refrigerant pressure to close the low pressure switch?
 
I will try this tomorrow after work and report back. Wasn't sure if it was of to kickstart it to test if it engages, but will def try.

I am getting about 100 psi on both sides, but it wont take any refrigerant at all. which i think may indicate there is no power to the compressor (at least per this).

I tested the electric from the compressor to the firewall and on the other side on the interior and all have continuity. But from there not sure where it goes and under the dash is impossible to get to w/o dismantling everything, so wanted to again check here for gut feel.
 
jpstewart19 said:
No as i said above I replaced a bunch of parts...there is zero refrigerant in the system
Click to expand...

Then you should easily be able to weigh in a block charge. And maybe since you havent, the low pressure cut-off is preventing the compressor from running.
 
If there is no refrigerant in the system, the compressor will not cut in. You have to charge it first. With a 6 hour vacuum and no leaks, it should pull in enough refrigerant to make the compressor cut on. If not, either you're doing something wrong, or have a part failure somewhere.
 
jpstewart19 said:
Any details on how I can do this? Not familiar and learning as I go.
Click to expand...

Will be painfully honest (and believe me im trying to help you).... refrigerant handling is dangerous, and you can ruin parts that are no longer easy to get and replace. Find someone with some experience to get the thing going for you.... You'll be a better man for observing this one for the first time anyway....

HTH, Lefty71
 
If you show 100psi on both sides, then there is SOMETHING in the system. If you didn't charge with any refigerant, then you have introduced air somehow. Evacuated for 6hrs, or system held vacuum for 6hrs ?? Evacuating for 20 - 30 minutes is usually sufficient. System must be at least partially charged before compressor will activate due to low pressure cut off switch, as others have indicated.
 
65wgn440 said:
If you show 100psi on both sides, then there is SOMETHING in the system. If you didn't charge with any refigerant, then you have introduced air somehow. Evacuated for 6hrs, or system held vacuum for 6hrs ?? Evacuating for 20 - 30 minutes is usually sufficient. System must be at least partially charged before compressor will activate due to low pressure cut off switch, as others have indicated.
Click to expand...

sorry maybe I musunderstood the question. My answer was with the system on and running. With it off it was steady at -30 for quite a while
 
Ok got home and applied 12v to the compressor and it immediately kicked on. Is there an easy way to test the pressure switch? Feeling optimistic
 
Not sure what year system we are talking about here, but most use low pressure cut off switch to control compressor positive voltage, so with system fully charged (or good partial) and max AC selected, you should have 12 volts on both sides of low press cut out switch connector ( with it plugged into switch, of course). Or you could unplug it and jumper terminals and see if compressor runs.
 
Thought I would close this thread out with a final update. After a bunch of torture, I replaced the low pressure switch, which also did nothing. But what did was the stupid fact that the conversion fitting I put on were setup in a way that the 134A quick connects were not engaging the Schrader valve. Once I eliminate them and restore the old connections, I was able to pull a vacuum that held, and charge right up w/o issue. Clutch engaged, very cold, seems to be working well so far.

Thanks again for everyones input on trying to get this working.
 
There is a LOT of failures with various adapters/ tools for access ports.
 
If the rpm drops and the clutch doesn't engage it sounds like you have a electrical short to ground dragging the alternator down.
 
KizaruMars said:
If the rpm drops and the clutch doesn't engage it sounds like you have a electrical short to ground dragging the alternator down.
Click to expand...

His issue was the properly working low pressure switch was preventing compressor engagement, due to the lack of refrigerant charge.
 
Lefty71 is correct. The final issue was the connectors were faulty so it wasn't taking a charge. Once fixed I was able to pull and hold a solid vacuum, then charge the systems and it kicked on right away. Still nice and cold 3 weeks and counting.

Although I did have to put a makeshift hose in place under the passenger side when I discovered the original was missing and condensation was pouring onto my floor matts. :)
 
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