Technical > Automotive > [Help] AC charge and compressor cycling

[Help] AC charge and compressor cycling

First off, what kind of gauge did you use? Was it one gauge like the kind that comes with most cheap charge kits? Or did you have two gauges, one hooked to each service port?

If you have two gauges, the system is badly undercharged, but I can't understand why it wouldn't cycle after adding a small amount. Something is missing in your information.

reply to tao
As long as you're aware that:

1) Most pressure measurements are not done at idle, they're done at a set RPM (usually 2k) to even have any relevant basis

2) If you're low on refridgerant it's because you have a leak. Refridgerant doesn't burn, anything you add will be gone in a short while until you find where it's leaking using a dye or other method

3) Using any sort of stop-leak will ruin your entire system in the end, so don't even bother.

reply to mattmag
The gauge was what came with the Walmart purchase, I think the company is IDQ. The readings I am giving you are from the low side top pressure and minimum pressure as measured by the cheap gauge.

I don't understand why the compressor would not kick on either, this is why I posted. I don't think the compressor is bad, or I am hoping the compressor is not bad. I know there is some sort of sensor somewhere and I am hoping that is cheap and easy to fix.

reply to dsanfte
I appreciate your advice. The small amount that was used indicated to me that the refrigerant was not low, so the problem lies elsewhere. Compressors are never cheap. I don't think it is the compressor anyway, the air should be colder though. Girlfriend said cooling has lessened over a two year period, that says leak to me. However, the applied fix indicates otherwise. Thank you.

reply to tao
Google search on AC, prompts me to post here that the compressor does cycle. Stated to me that AC has always worked better at idling at a light.

reply to tao
It could be the air diversion doors in your air handling system. One of the doors may not be closing all the way or the seal is messed up. That would allow hot air from the heater core to be mixed in with the air from evaporator resulting in warmer temperatures.

Hmmm, wonder how to fix that without getting myself upside down in the car?

Well, I took the car out for a 30 mile spin on a 85 degree day. I am sold on two things: one, it is likely the blending door, two, it will go to a repair shop as the GF will not let me take her dashboard apart.

Happy Memorial Day and I hope where you are is warm, sunny, and with a nice breeze. Thanks to all who have passed through our lives and made our's better.

Smart Girl Friend

reply to tao
Cycling between 25 and 45 is a touch high -- should be more like 20-40 or 21-42, but that's with an accurate gauge not one of those cheap "death kit" gauges.

"high side" generally refers to the high pressure service port. Measuring that requires two gauges, so I assume you are using that phrase to refer to the upper limit of the cycling on the low pressure port? If it is cycling, then the compressor is engaging. QED. Now, if the system is overcharged (as when someone just starts adding cans of refrigerant to see if it helps) it does not cool as efficiently and effectively as when it is properly charged.

If you continue to overcharge a system, the pressure may rise dramatically, especially when a slug of liquid hits the compressor. If the slug doesn't kill the compressor, some cars have a high-pressure switch that will protect the system by shutting it down. If you are correct and the compressor quit running altogether, that might be what is happening in your case.

The ONLY WAY to properly determine the system charge is to recover the contents, evacuate the system, and recharge by weight according to the underhood sticker. There are no short cuts, tricks or magic kits that can change the physics.