A/C woes

I live on the coast, so don’t use the a/c much. Just turned it on for the first time this spring. Here are the conditions:

Switch light inside is yellow not green when pushed in. Fan runs but no cold air.

Pressure on high side is good when the a/c is off but as soon as I push button it drops to zero.

Checked the fuse: good

Clutch was spinning all the time when the key was on, even without the switch on. Removed the relay, clutch stopped spinning.

Checked the clutch with a jumper from the fuse box- clutch engages.

Checked the clutch with an external power source @ the clutch- clutch engages.

Replaced relay- clutch is static without the switch on. Engages when switch is on. Still no cold air.

Pressure still goes to zero when clutch is engaged. Still no cold air.

Of course I fear the compressor is gone, but can’t be sure. I don’t have a problem with replacing it since I’m going to change the serpentine belt and idler pulley, and I feel competent enough to do it.

Is there anything else to check before I bite the bullet and get a new compressor/clutch assembly?

 

That's correct for a 2nd gen.

You must mean low side, the pressure on the high side would increase when the compressor is engaged.

Without having both high and low side pressure readings your kind of flying blind but the pressure being very low on the low side would suggest it's either low on refrigerant, the condenser is restricted, or the expansion valve is stuck closed/plugged, typically you want to see somewhere between 25 and 45 psi on the low side and 150-250 on the high side with the system running depending on ambient and cabin temp.

If the mode selector is set to defrost or floor/defrost the A/C will turn on regardless to weather or not the switch is on.

 

The push button LED is yellow on my truck.

I had a weird experience earlier this year where the A/C would not provide cold air for 2 days (90 miles driven each day). I had just returned from 4 weeks in Europe, and had disconnected the battery while I was away. I brought the truck to a local A/C specialist, and they reported no fault found ($70).

I posted about it here and another member stated that he had the same issue after the A/C was not run for a long while (months).

I have since chalked it up to a quirk of these trucks.

 

This is from the 2013 FSM but it's pretty universal

 

Thank you, tak1313

 

I’m back to this today. I have a whole new set of circumstances. Last week I replaced the relay. I have a manifold gauge setup on it now.

The clutch does not spin when the ac switch is on inside. Removed the new relay and tested the clutch with a jumper> clutch spins. Left the jumper in for ~3min. Zero pressure on either side. Didn’t even jump.

So now, I have the clutch not spinning when the relay is in/switch on, clutch spins when jumped past the relay, and even when clutch spins, there is zero pressure on either side, verified by pressing the valve in either port, on or off, no gas escapes. Clutch will not spin under any control condition with the relay in, but spins readily when jumped.

I had some left in one of those chickenshit 134A bottles and I tried to put some in. The gauge on it registered 0 too, but I squeezed the trigger anyway for a few seconds. When I checked the high side port, the manifold gauge showed 0, but I removed the valve and pushed the pin and got a whiff coming out but went way in a second or two.

Kinda scratching my head here. Started to do the procedure outlined by tak1313, but didn’t even get to the first step.

 

So there's no refrigerant in the system which means it leaked out, so you need to find the leak.
Compressor will not run if the system is empty.
Don't use those quick-charge cans, almost all of them have stop leak in them which will wreck an A/C system.

 

Thank you. DM93

Any step by step stuff about leak detection and remedy? Any common leak spots? Recommended UV agent for leak detection? Do I understand you to say that, if there is no refrigerant in the system, the clutch won’t run?

 

@Dm93 is correct - there is a sensor that monitors refrigerant level via pressure within the system. If it drop below a certain threshold, it disables the compressor because running the compressor without refrigerant can permanently damage it because the oil circulates with the refrigerant.

For the system to be entirely empty (assuming it's not that you didn't open the valve to the gauges), it would be a pretty big leak if it ran ok fairly recently. A common reason for such a big leak is a rock or road debris puncturing the condensor in front of the radiator.

A dye is usually injected with refrigerant and the system is run. They dye (usually UV) will then show where the leak is via UV light. There are dyeless methods as well using a refrigerant detector around possible leak points or even an ultrasonic microphone to listen for the high pitch of escaping refrigerant, but those require specialized tools that can be fairly pricey. UV dye is the cheapest method.

 

Thanks again, tak1313.

I made an adaptor to pressurize the system with air through the yellow supply hose of the manifold. I used 70# air pressure. The gauges shot up to 70 immediately. So far I cannot detect a leak with a microphone that I can listen to the neighbors pee. The 70# pressure both gauges has held for 2 hrs. When I remove the air- bang, zero. Again, I tried to get any pressure when the clutch is running. Had to monkey jump the relay again to get it to run. No pressure, running or not.

I’ll pump the system out and fill with 134a and see what happens.

What should my pressures read when filled?