Yet another A/C problem/question thread

[WeeYari]

After reading as many threads as I can, I'm still unsure of how to diagnose a no cold air issue.

What I am seeing and experiencing;

- no cold air at all, not even briefly
- no typical drop in RPM when a/c engaged via climate control button
- no bubbles visible in sight glass

What I have done;

- check all fuses and they are good
- briefly depressed low pressure line valve and pressure was released
- cleaned pressure switch connector

When I depressed the line valve, bubbles did appear in the sight glass. These went away once engine was restarted. No subsequent bubbling appeared.

It should be noted that I do not currently have access to pressure gauges or a multi-meter, so I cannot perform any diagnosis that involves those items.

Finally, a rookie question. Visually, how can I tell if the compressor clutch is engaging since the pulley is always spinning? I'm guessing that if the disc located on the left side of the a/c pulley is spinning, then the clutch is engaged. If that is the case, then my clutch is always engaged.

Thanks in advance for whatever insight can come my way.

[shepd]

Harbor Freight has gauges for $49.99, on sale right now. By the time you factor in exchange, driving and HST, that's still less than $100 CDN. Get a set, it will do you well. Pick up some R-134a while you're there so you can fill the system if you need to (after repairing, of course) since you can't buy it in Canada without a license. If you have an air compressor HF sells a venturi based vacuum for under $20. You may as well pick up some A/C line disconnects while you're there.

Those three tools are *essential* to repairing an A/C system.

Anyways, since there's refrigerant in the system, if the compressor was working, you'd know it by feeling the high pressure and low pressure tubing. Low pressure should be cold, high pressure should be hot. If that is not happening, but the compressor runs, the only two things possible are either a blockage or compressor failure.

However, most vehicles, including ours, will refuse to engage the compressor if the refrigerant level is low. You'll still see plenty come out if you try to release it, but it's too low for the low pressure switch to disengage. If you force the compressor on (with most cars you'd just need to hotwire it) as long as there's even a small amount of refrigerant you'd see the system get cold in a hurry (in fact it will ice up due to too little refrigerant). That could give you the answer you seek. It's also possible that the high pressure detection turns the system off. That would only happen due to a restriction or someone filling it far too much. In either case, forcing the system on with a restriction or overpressure would not cause any cooling. It could, however, cause the compressor to release the overpressure valve and vent refrigerant. It could also cause the compressor to blow up, so... yeah... :) Fun times.

I feel I should say forcing the compressor on can quickly lead to damage even if it's low or no refrigerant due to a lack of oil. Do not use this method to get A/C in the car, just use it for a couple of seconds to test. Preferably, use gauges.

If you have low pressure, you have a leak. Time to buy a UV pen and start searching for it... When you refill, ensure any extra oil you add has UV dye in it, or add it yourself!

[invader166]

I learned a lot about the AC system from these 3 videos, and it also answers a lot of your questions as well::

http://m.youtube.com/watch?v=pCv7rCdcXsc

http://m.youtube.com/watch?v=SHg2xRMnM38

http://m.youtube.com/watch?v=rulXlnG2Unk

[CTScott]

The easiest way to tell if the compressor is engaging is to have someone else turn the AC on while you listen with the hood open. You will hear the click of the compressor engaging and will hear the difference in sound with it engaged.

As stated above, low pressure can prevent the compressor from being turned on by the AC ECU, so just verifying that there is some pressure in the system is not sufficient.

[WeeYari]

Update on this;

Finally got around to performing some driveway diagnostics. After confirming fuses good, pressure sensor operational, static line pressure within specs I caved and took it in to Toyota to diagnose. At this point I figured I was left with either a mouse chewed wire somewhere or a shot compressor. Turns out my compressor is seized. Their quote to repair is about 1/3 the value of the car at this point. So I either continue to cook, or look for used/refurbs.

[ern-diz]

Update on this;

Finally got around to performing some driveway diagnostics. After confirming fuses good, pressure sensor operational, static line pressure within specs I caved and took it in to Toyota to diagnose. At this point I figured I was left with either a mouse chewed wire somewhere or a shot compressor. Turns out my compressor is seized. Their quote to repair is about 1/3 the value of the car at this point. So I either continue to cook, or look for used/refurbs.

Ouch. Any idea what caused it? Just a typical end of life thing, or did it just go wrong?

[rningonfumes]

Is a compressor replacement that expensive? It's not like they have to open of your dash to get to the evaporator or anything.