a/c compressor shuts off after 2 seconds

[Mephisto]

had to drain the AC condenser when i took the front clip off for the motor swap. Today I got a AC recharge kit to refill it. I turn the AC on max cool for a few minutes, the compressor kicks on and spins for about 2 seconds and then shuts off, then in 5 seconds it turns on for 2 seconds and shuts off. It does this non-stop as long as the AC is on. I filled up the condenser till the little gauge on the recharge bottle said to stop. But no cold air is coming out of the vents. When the compressor turns on the gauge on the recharge bottle drops down to empty then goes back to full when the compressor shuts off. Haven't seen this problem before. Could there be air in the lines preventing the compressor from working properly? Would the compressor even turn on if it was dead?

oh and the previous owner had the GMC dealer convert the AC system to R134, if that makes a difference.

 

[blacktyaffair]

Re: a/c compressor shuts off after 2 seconds

Did you pull a vacuum on the system before adding the refrigerant? The gauge on the refrigerant can needs to stay in the "green" while the compressor is running. When the low side pressure gets too low it will shut the compressor off. How much refrigerant have you added so far? I'd say it needs more.

 

[Logan]

Re: a/c compressor shuts off after 2 seconds

Pull vacuum on the system first and foremost. Also, did you add oil? You will need to add some to make up for the loss.

Second, when filling the system you need to jump the pigtail that connects to the top, back side of the compressor which basically activates the compressor because if the clutch isn't engaged when you are filling the system you aren't actually adding any Freon. You will know it is working because the clutch on the front of the compressor will engage. Also, turn the AC switch in the cabin on MAX and the blower on high for testing purposes. Bring the system to full. I aim for the low side of the green mark on the gauge because A/C systems will actually cool better with less refrigerant from my limited understanding of them.

Hope this helps, oh yeah someone will chime in I am sure but you may have to jump the pressure switch pigtail on the evaporator....I don't really remember which one it is. Been awhile since I have messed with HVAC stuff.

 

[Adam#0213]

Re: a/c compressor shuts off after 2 seconds

On the charge you put what the factory labels says.Less refrigerant does not mean more cooling.I hope you did a leak check on everything you had opened.Pull a good vacuum on the a/c.Any other questions LMK I work on commerical/Industrial refrigeration. I have done my own a/c work for a long time now.If you guys need any help with your furnace/a-c will help anyone out.

 

[SY2932]

Re: a/c compressor shuts off after 2 seconds

I finally broke down and bought all the stuff to do AC service (vacuum pump, manifold gauge set, dye injector, etc) last year when it was "walking on the sun" temperatures for a month+. My wife can't take the heat and I wasn't about to drop $1500+ to get the AC serviced on her Trailblazer.

As mentioned above if you have had the system opened up, it is MANDATORY that you have the system pulled down with vacuum for at least 30 minutes to get all the moisture out. The reason is twofold. First, the refrigerant and moisture form hydrochloric acid when they react together. Second, the moisture can freeze in the orifice tube and limit the refrigerant flow in the system.

Since you had your system opened up, you will need to replace the accumulator or drier (big aluminum can in the engine bay on the passenger side towards the firewall). Usually, one ounce of fresh clean refrigerant oil is added to the new one before you install it.

The orifice tube will also need to be replaced. Don't let the cheap price of this component, usually less than $2, fool you since it will have a MAJOR effect on the performance. These tubes like to get plugged up and when they do, restrict the flow of refrigerant in the system. All things being equal, a car with a partially clogged orifice tube will blow cool air whereas one with a new unrestricted one will freeze you out. It really makes that much of a difference.

With regards to refrigerant capacity, every system has an amount that it needs to operate efficiently just like like the amount of oil that you put in the crankcase. Some systems have it called out on a sticker somewhere in the engine bay. On others, you will have to do some research to find out how much it needs. Bottom line is once you know what that number is, you need to KNOW how much that you are putting in. I use a small digital scale to keep track of how much I put in since I can purchase a 30 pound tank of R-134a for $100... Just an FYI if you ever use a bulk tank, you invert the tank so that liquid instead instead of vapor is released when you open the valve.

Given your situation this is all kinda academic since this only scratches the surface as far as how to service the AC and how it works. It's not so different than members having transmission issues and expecting a cut and dry "fix and/or replace this part and your problem will be fixed" :lol:. It's not that easy and AC service requires special tools and equipment to be done *correctly*. The importance of pulling down the system not only prepares it for the introduction of refrigerant, it will also verify that you have no leaks anywhere. No doubt, these trucks are money pits. However unless you want to spend some money on specialized AC tools, you are better off taking it to a shop :2cents:.

 

[Mephisto]

Re: a/c compressor shuts off after 2 seconds

hahaha and I thought this was going to be a simple go to pep boys buy this thing for $35 and you're done situation...

I'm completely AC illiterate as if you couldn't already tell haha... so "pull a vacuum"? should I be hooking something up to that lower nozzle by the wheel well???

Mike you're saying I gotta replace the accumulator??

mmm yeah.... i think I'm gonna have to go with your last statement on this one and just bring it in to an AC guy haha. Gotta replace the relay or resistor for the fan anyway as I got the "HI" only problem too.

Probably just use this freon can to recharge my DD and get SOME use out of it.

 

[SY2932]

Re: a/c compressor shuts off after 2 seconds

Here is a short video showing how it is done. You connect the vacuum pump and introduce the refrigerant on the low side of the system via the service (yellow) hose.



My setup is identical except I have mechanical gauges on my manifold set instead of digital. If you still want to go the DIY route, you can pick everything that you need for a couple hundred .

Yeah, you will need a new accumulator because it has a desiccant inside that will absorb any moisture that might get into the system. Since you had the system open, it will saturated with moisture and therefore worthless.

 

[atkonkler]

Re: a/c compressor shuts off after 2 seconds

Take it out , who needs air conditioning when you have windows and are driving , I call it 60 mph air. Just another thing to drag down the truck and lock up and smoke belts!