OK, so my entire ac system has been replaced over the last 2-3 years and somewhere in the process a very small undetectable leak has come up. It needs charged just a tad every 10-12 months. When I am running at speed it blows ice cold, but when I stop at a light it blows hot. I picked up a kit from the auto parts place to add some 134a in it, but when I run it at idle the compressor does not kick in long enough to keep the pressure from spiking on the gauge. Should I just add some until the compressor stays running like it says or run it down the road to get it blowing cold and then stop and add some? When I saw the pressue max out the gauge it worried me some.


Thanks.

 

Yes, keep adding some till the compressor stays on, the reason it spikes is its equalizing from the pressure in the can (yes cans have alot of psi in them), no harm, thats normal when the compressor doesn't run. Sounds like she just needs a bit more.

 

Bob just posted something simliar, hope this helps, some good youtube links on this thread

https://www.dieseltruckresource.com/...n-t272323.html


You should really get a manifold gauge set, that way you can see what the high side is doing, the suction side of the compressor really won't tell you much. Best to know both sides. Sometimes compressors start to fail, people put to much in and overcharge it, thus high psi on low side, and low psi on high side means bad compressor. Overcharge will kick off the high pressure switch which stops the compressor, and not good for hoses etc.

 

Thanks, those links were great. I'll attack it again in the morning.

 

i just recharged mine with amanifold gauge set. i had to put a large fan in front of the condensor to keep the high side from getting too high. not sure whats going on but my fan wasn't kicking on when the a/c came on. my theory is that at idle/low speeds the fan doesn't move enough air over the a/c condensor and it can cause too high of pressure in the system and bleed off the charge through the releif valve (i think its on the compressor). so if you have an undetactable leak just a thought...

 

How to tell if ur system needs to be recharged or not?? Here's the issue I'm having. It blows cold air....cold enough that you could "hang meat" in the cab. But when I want to temper it down...adjust the thermostat so to speak in about 15 mins. it freezes up and nothing comes out of the vents. Could this also be related to a "low refrigerant" problem also??? TIA

Jim

 

Have a look at this thread. It says want you confirmed about no air moving across the condenser and other things that might interest you.

Also, the sticker on my truck says the capacity of the system is 1lb of R134A. So I guess it does not take much to get it up to speed.
Never did it before, but I noticed a can of 134 most of the time is 14oz's.

https://www.dieseltruckresource.com/...ight=Vent+Temp

 

That's a good sign of a low charge symptom,,, when the fan is on high it moves enough air to keep the evap. defrosted, low speed lets it freeze up because of the condensate forming and freezing up, no air movement through the coil.

Check your drain also to see if it's leaking the condensate out of the box.