Hey all,

I noticed lately that either my ac is not as cold as it used to be, or I just hadn't ever used it when it was really hot (I normally use windows when my wife isn't with). Its still cool, just not ice cold. I have also noticed in the past that at idle my ac compressor will lock and unlock regularly. I was reading about ac issues now to try and see whats up and discovered that the locking and unlocking probably means my system is low on pressure. Now I'm looking for advice on how to deal with this. Should I try a do-it-yourself can from autozone? Ive been told in the past they are dangerous and not the correct way to service the system, but I've been reading and a lot of guys say they use them with great success. Is it worth a try or not?

Ok that makes more sense now. Unfortunately I don't have the equipment to see all that. I guess what I'm asking is, why was I not able to charge above 25 psi? And if I set high idle and the compressor unlocks too much Would I be able to add more freon with the rpms up?

Edited August 5, 20168 yr by leathermaneod

Because as you discharging the can into the system the can got cold. So what I typically do is fill a small bucket or pail up with hot water and place the cans in hot water to regenerate pressure. Basically you need to keep the freon above the boiling point.

Ah now I understand. It would be nice if the instructions had told me that lol I'll try at higher rpms and a warm can when I get home and see if I can get it charged up a little more 

134A boils (changing state from a liquid to a gas) at -15.34°F.  When the 134A is discharging from the can both the volume and pressure drops in the can when that happens the temperature drops also.  Bring the heat up and the pressure comes up.  I believe this is the equation for it  P₁V₁/T₁=P₂V₂/T₂.

Thanks a lot guys! Mike, I followed your advice with the warm water and heating the can up in between charging. Got about 35 psi now but that was at 89° so it should be more like 50 psi per the fsm, but I've already added about 32ozs of refrigerant. I did get it to where the compressor stays locked at 1500rpms now, but on my way home I had max AC on for a while before it got cool enough to turn it down. I'm wondering if it's still not enough psi to keep the comp locked at 2000 rpms which is where I spent most of my 5hr drive.... don't get me wrong it was cold, just not that cold. I'm going to check tomorrow and see if the comp stays locked at 2000 rpms. If not should I add more refrigerant?

I would stop there. Like the foot states if the pressures are below and discharge temperatures ar good then your fine.

What if the compressor isn't staying locked at higher rpms above 1500 though? 

Here is where I need to see the high side pressure. I need to be able to look at lo and hi side and then I can base the amount more so. 

Well I'm at my inlaws right now and my father in law has a gauge manifold so maybe I'll hook it up tomorrow and see what it looks like. What do I need to know/look for when doing that?

Well here are the results from testing with the manifold gauge. 

What do you think? Add more freon or no? Compressor stayed locked at all speeds. Outside temp is 86° and very humid. Air at the vents is pretty cool, just not ice cold yet. Even at highway speeds I don't feel like I can take it off max AC for a good while.

 

Idle:
Comp locked:
High-230psi
Low-39psi
Comp unlocked:
High-
Low-

 

1500rpm:
Comp locked:
High-283psi
Low-30psi
Comp unlocked:
High-
Low-

 

2000rpm:
Comp locked:
High-285psi
Low-27psi
Comp unlocked:
High-
Low-

Edited August 6, 20168 yr by leathermaneod

You pressure numbers are fine just the hi side showing that the condenser is running a bit hot and not discharging heat very well. Fan clutch might be weak or the condenser is plugged up with bugs.

Test the center air duct temp with the A/C off first to see if it is the same as out side air and be sure the blend door is closed all the way.  Then run the A/C through the enter vent on max A/C (this stops out side air and is in recirculation mode) turn fan on to #3 bring rpm up to 1500 and if you can put a fan in front of the radiator and turn on med to high speed.  the fan in front of the radiator and 1500rpm simulates driving at about 35mph and you should see a duct temp below 35°

Thanks @IBMobile... That good info... 

Thanks guys for all the great info! You've been very helpful and I've learned a ton about AC! I've got to drive home tomorrow so I'll see how it does. If it's still not cool enough, I'll test the actual vent temp as you suggest when I get home.

Edited August 8, 20168 yr by leathermaneod

As for testing vent temp buy a cheap digit kitchen thermometer and use it for testing the vent temperature. I've seen weird reports from IR temp guns and different color changes the temperature displayed. 

My thanks to @IBMobile and @Mopar1973Man for all the useful info too. It has helped getting mine going again.

Just thinking about this @IBMobile might be a good idea of teaming up building a new A/C article built around both of our ideas. It would be awesome. 

A thought similar to that ran through my head this morning   I'll pm you later.

Or... Just give me a shout at (208) 628-3645 we can talk about it.

Edited August 7, 20168 yr by Mopar1973Man

Just wanted to throw something else out there that might help others. I didn't even think of this until Mike mention that my condenser might be plugged with bugs. This is what it used to look like

Not so many bugs, but there was an awful lot of surface area that was bent over so that no air could pass through. I realized this and that it was likely part of my problem, as well as the fact that it was probably greatly restricting air flow to the intercooler and radiator. This is what it looks like now

Not great, I know, but a vast improvement over what it was :-) I used a radiator comb, plastic fork handle (i couldnt find a plastic knife), finger nails, and A LOT of patience lol