AC Questions

[Sean J Blackburn]

Hi guys,

I need some help with my truck. I parked it last night after work and the ac was working fine. Got in it this morning and no cold air.

It seems the compressor is not turning on and the condensor fan is also not turning on.

I have checked every fuse labeled for hvac and they were all fine.

Put gages on it and got 56psi low, 75 high for static pressure, it was 110 out when I did this. My understanding is that the static pressure should be much higher at this temp.

When I started the truck with ac on I showed 0 on the low side and 125 high side, but I don't think the compressor was clicking on.

My questions: does this just seem like a low refrigerant charge? If not, where should I be looking next? Seems like it'd be unusual to lose the refrigerant charge overnight.

Thanks for any help, it's way too hot to be without ac!

 

[fitteenhundred]

With those pressures it looks to be low on charge. Static pressures should be over 100. I would guess when you started it up the compressor came on and pulled the low side pressure down and then tripped right back off on the low pressure switch. Watch the gauges while you start it up and see if the pressure drops again.

 

[Sean J Blackburn]

Thanks for the advice. I'll take a look at the gauge while I start it up in the morning. Hopefully it's just low and that's what is keeping the compressor from engaging.

 

[Daw14]

Sounds like it is low on refrigerant and kicking off on the pressure switch. May think about adding some dye when you recharge,so as to help locate the leak , unless you have a leak detector.

 

[Sean J Blackburn]

Thanks guys. I am in the process of adding refrigerant with some dye. I'll update once I'm done.

 

[mikeru]

Be careful when adding refrigerant. Adding too much will damage the system. You have no idea how much is in there now, or how much to add. If you are low they there is obviously a leak. If there is a leak and the system pressure was at zero at any time, moisture could have been introduced into the system through that leak. It doesn't take much moisture to cause problems. If it were me I'd locate the leak, discharge the system, and fix the leak. Then pull a vacuum on the system and recharge with the correct amount of refrigerant.

I miss the days of R12 systems, where you could just watch the sight glass and add refrigerant until the bubbles stopped LOL.

 

[Sean J Blackburn]

I actually dropped it off at a trusted shop this morning because I don't have a vacuum pump to Evac it and as noted, something is obviously leaking. Currently waiting to see where the leak is. I do most of my own work but with ac I don't have the tools to do the job. Plus it's 110 degrees outside and I don't want to be out there working

 

[Jeepwalker]

Aaaahhhh....the "trusted shop"... lol

 

[mikeru]

I actually dropped it off at a trusted shop this morning because I don't have a vacuum pump to Evac it and as noted, something is obviously leaking. Currently waiting to see where the leak is. I do most of my own work but with ac I don't have the tools to do the job. Plus it's 110 degrees outside and I don't want to be out there working

That's probably a good choice. A/C work requires another level of knowledge above normal wrenching. It's not rocket surgery though, if someone wanted to learn it there's plenty of good information online. The biggest pain for me is locating the leak, and purchasing refrigerant. The small 12 oz cans of R134a have been banned in my state, so the only way to buy it here is by the 30 lb bottle, and requires a license. Luckily for me I live about 45 minutes away from Idaho, which still lets you buy those.

 

[Sean J Blackburn]

Update: there was only a third of a pound of refrigerant in the system so it was way low. They evacuated and recharged (and added dye) and ran it for an hour, didn't see any obvious leaks. Going to bring it back in two weeks so they can try to locate the leak once it's had a chance to run for a bit.

 

[Sean J Blackburn]

Update: took it back two weeks after they added dye. They had it all day and were unable to find any leak with a uv light or electronic sniffer. Said it probably has a tiny leak somewhere that isn't big enough to show with the dye or sniffer. Told me to bring it back in two more weeks and they would do another check and top up the refrigerant for free if it is low. If they can't find the leak I will probably just have the system charged once a year in March when it starts getting hot here