AC doesn't get cold until the engine fully warms up
 

SOLVED, READ POST #12 FOR SOLUTION

Hi all, I'm having a really weird problem with my AC.

Immediately after I turn on the engine the AC will be cold and then it stops being cold after 20 or so seconds. It'll stay not cool until the engine fully heats up (you can see the temp drop several degrees from the thermostat opening) and then it'll suddenly start blowing cold air.

--The clutch electromagnet (OEM AC Delco) is only about 3-4 years old and it's not behaving like a weak coil, but I checked it to see it it was just too weak. During the time the air is lukewarm, the coil isn't even trying to engage as suggested by putting a screwdriver next to it. After the engine warms up, the clutch engages no problems. No slipping. And cycles just fine.

--Maybe a pressure sensor problem and the engine heating up warms the refrigerant lines to increase pressure enough to trip the sensor? Nope. Replaced both the high and low side sensors and nothing changed. OEM AC Delco parts.

--Refrigerant pressure is also normal.

When it starts working after the engine warms up, it's cold and stays cold. No problems. And if I turn the engine off and run a brief errand like a cup of coffee so that the engine is still hot when I get back, turn the engine back on and the AC is fine.

It's a '96 Chevy.

Only thing I can think of.....electric fans may not be working until the engine gets hot and then the fans come on because the coolant is hot.......

.

Chevy what?


+1. Your A/C needs the fans to pull air over the condenser and they should come on right away with the A/C or defogger.

Sorry for the much delayed reply.

It's a '96 Chevy Silverado. There aren't electric fans, just the belt-driven one and it's working fine. The clutch is flat out not engaging or even trying (not a weak magnet), but once the engine runs for a bit it starts cycling like normal. I had a weak magnet a few years ago and replaced it. The signs are completely different than they were then.

Is there maybe a component of the compressor that's having problems?

The A/C system isn't that complicated. There's only a few parts that measure/sense or turn on/off. High/Low sensors, compressor, clutch magnet, fuses, and the dials in the cab, as far as I can think. But I'm at a loss for what would make the compressor cycle on/off when I first start up the engine, then stop for several minutes, and then start cycling normally for as long as I drive.

No takers? I agree it's a very difficult thing to diagnose.

The A/C system on your truck probably also doesn't have a lot in common with most of the cars discussed on the site.

Actually it maybe quite simple, from here I suspect its just low on coolant. Either try adding a few ozs and see if it remys the problem OR put a set of gauges on it and watch the pressures. As the engine warms up the coolant in the AC expands and as it expands it comes up to enough pressure to activate the compressor. Good Luck

+1 for a weak fan clutch or fan shroud housing damage

Do you guys even reead the posts? WTH why post up useless crap?

I rechecked the pressure and it's in the operating range but on the low end. I'm going to grab a can of R134 and get it up to the middle of the operating range and see what happens.

What I would do is see what the pressure on the low side is when its not working. I'll bet its just low enough to cut off the compressor.

Thank you for all the replies, everybody.

Turns out it looks like my pressure gauge needs replacing, maybe. I added a can of R134a and it's working fine now. It's on the upper half of the operating range now, per my gauge, as opposed to previously being on the lower end of the operating range.

Hey thanks for taking MY HELP...............

Harbor Freight gauge set. I have a couple rigs where close isn't close enough, had to have both high and low side and the ability to bleed back as well as fill..

Its good enough of ra once a year ac adventure..

You win the Internets, RockinWs6! :hail::hail::hail:

But it's great the A/C works right. Texas starts getting warm in March, so it was something that needed to get taken care of soon. And I'll visit Harbor Freight and check out a new gauge.

Everyone else blew you off....... TY


I know I'm great.