usarmyrangrs, yeah when i turn the dial to cold it was cold, and then when i switched on the heat it blew hot hot. In your reference to the sound it seems as though the compressor seem not have to try as hard when turning on the heat vice (sorry military term) when switched to cold it seem the tick sound from the compressor is more louder and you hear like the engine kinda rev down.

 

Does it alternate between hot and cold at any driving speed? Slow, fast, idling? Are the fans indeed turning on? Check that... be sure the cooling fans in the engine compartment are turning when A/C is on.

 

Your AC is what’s called ‘cycling’ and is perfectly normal. During the ‘off’ (compressor not running) cycle, the cooled hot liquid refrigerant stored in the condenser still has enough pressure to fill the evaporator and cool air moving across the evaporator. Some systems use a sensor to regulate the temperature of the output air, but the simpler systems don’t. Instead they’ll use the high pressure cutout (switch in the small diameter tube) to cycle the compressor. Think of it as filling a bucket with a small outlet. You don’t want the bucket to overfill so you stop filling it when you get to the top. Before it empties, you refill it.
But from what you describe, I think your problems lay elsewhere.
In a high humidity environment it’s possible for the evaporator to ice over. If the unit is boarder line overcharged this is quite possible. Another possibility for ice over is a clogged evaporator drain. When you park after using the AC, you should see a puddle of condensate under the car.
Another possibility is your evaporator is partly covered with garbage that fell through the air inlet in front of the windshield. You wouldn’t believe how much junk falls through.
Last and hopefully not your problem is the expansion valve orifice is partly clogged. This may have happened if, when the system was open, some dirt may have entered or the system wasn‘t properly evacuated (pumped down to remove moisture) before recharging. You’ll need to know the ratio of low side to high side pressures to determine proper expansion valve operation. A while back there used to be a window on top the receiver/dryer with a desiccant that would turn red if the system contained moisture.
These are the most common causes of long cycling and poor cooling that I know.

Good luck.

 

There is no such think as a dumb question. Especially with AC stuff. Unfortunately a lot it takes special equipment to diagnose probelms, like the whole rest of the car. I think the compressor should run along with the rest of the system however I know that when they test them they are tested without being hooked up to anything. Asa long as it has lubricant. I suspect the problem might be with the cycling switch or in the controller inside the car. I would try doing what you did a couple more times. If it keeps doing what it did then it's likely the switch or the controller. I doubt it's the compressor if it will blow cold air. Usually they either work or they don't. Let me know what happens.


Luke

 

Usarmyrangers thanks for jumping in on this one. This guy needs all the help he can get.

 

Hey guys,

sorry for late response... Duty Calls. So on the ride home from work today, it was blowing cold then hot, pretty much the entire 40 minutes. so i decide to pull over pop the hood and see what the compressor is up to. so i watched it for like 5 min , and it would cycle on then off about every 1 minute or so. then I did what you said earlier and threw over to defrost it stop for a minute and then kicked back on off while I had it on defrost.


So I remove the cycling switch and and naturally the compressor when from cycling to nothing, and hooked the jumper wires to the switch and the entire car died. So i started it back up and it did the jumpers to the switch and it died, again.. Any thoughts???


Oh ready what 01 camaro CP said, i might be mistaken on the clutch switch, i may have been jumping the high pressure cutout. Its in between the the bottle (accumlator) and the thing by the firewall. the evaporator right?

I did see a puddle of water underneath though when it was blowing cold.


and yes the fans are turning on as well.

Checked the low side and pressure still was 28psi.


I'm thinking more and more it may be the high pressure cutout the was mentioned before.


Your thoughts?


Thanks again

 

Well actually without the correct diagnostic equipment it might be difficult to isolate the problem beyind akk the steps you have akready taken. You have more patience than I would have had. I think at this point it might be worth paying a good shop or GM dealer to test the system. I can;t think of anything else to check for without having the equipment. A/C things can get complicagted and before spending a lot of money replacing things I think it's time to get a good diagnosis. Hate to have you spend any more time and money on it. Plus knowing what is wrong will help you in the future. When I take mine in I love to make friends with the techs and ask them all kinds of questions. It's fun and part of the automotive growing experience, I would like to have you let me know what it turns out to be be. Good luck with it.

 

It's almost beginning to sound like the blend door is acting up, but what would cause it to do that I have no idea. It's operating correctly, and suddenly turns hot... which would make sense that the door is partially opened, allowing air to flow past the heater core.

 

I'm agreeing with Skyrunner now. You need to have someone check out the system paying attention to the high/low side ratios. Best if you can get all three monitored, High (compressor) Mid (condensor) and low Suction side.

When the system is operating properly:
System off, not run for a while, all system pressures will be equal and well above 28 PSI.
With the compressor running, the high side pressure will rise while the low side goes down. With R-12 the ratio was roughly 10:1 ( 300 psi high to 30 psi low Not sure about R-134) These pressures will vary as the system cycles.

What to lookfor:
If the pressure goes below 28 psi on the low side --- you have a leak and need a recharge.
If the hight side maxes out and very slowly falls with the compressor not running, it's a sure sign of an expansion valve problem. Not an easy fix.

One word of advise, on these computer controlled cars DO NOT short out or jump ANY wires you're not sure of. Just too easy to cause damage due to over current through a circuit.

 

sorry for the late reply its been a while, so I took the car in again to perform a dianostic of the A/C, it came back with a leak in the compressor, which leads to believe that there was a leak all the time, and the previous shop overlooked it and just assumed it was the high pressure servive port. so i pissed away 200 plus dollars for a high pressure service port, which i found to be about 12 bucks at advanced auto.I'm testing some stop leak in there and we will see if that works. so far its been a week and still blowing cold.maybe i just slowed the leak. I confronted the shop that did the port and needless to say the wont be refunded any money to me... just wierd i guess that the compressor magically sprung a leak one to two weeks afterthey put the port on....