What a time for the A/C to fail

[automech]

I agree with number 2 , if system is cold, clutch engaged, your refrigerant is probably not the problem. I would suggest VOLTAGE DROP tests on ground and voltage supply wires at the compressor. Check for good ground first then backprobe the voltage feed to check while in operation. If your voltage supply is good when your clutch stops working you have a bad clutch coil. If the volt supply stops, you need to go backwards towards the source. Wiring diagram would be helpful at that point.

 

[sunnyside360]

Lots of bubbles will indicate low refrigerant levels.

Before I get jumped on, I know all about the need for gauges etc, but people still charge their own systems without them, no matter what anyone says. Looking at the sight glass is a good first indicator of "possible" problems as indicated in my manual and from past experience.

I'm a little slow at this A/C stuff but getting smarter (I think). I either read or someone told me most all A/C issues stem from low refrigerant. So I added a can (12 oz) and now realize that was the wrong thing to do w/o knowing for sure. I've blindly added R12 to older systems and R134 to newer cars and trucks and it always helped to improve the cooling. But, I may have screwed up this time and the only way of knowing for sure is to check the pressures. I'm off to Napa in the next hour to get a set of manifold gauges. I checked Harbour Freight and they have them but there are a lot of negative reviews.
I've put off buying a set for years but think I need them now. First, I'm going to check the voltage at the compressor and try to trace back.

 

[sunnyside360]

I agree with number 2 , if system is cold, clutch engaged, your refrigerant is probably not the problem. I would suggest VOLTAGE DROP tests on ground and voltage supply wires at the compressor. Check for good ground first then backprobe the voltage feed to check while in operation. If your voltage supply is good when your clutch stops working you have a bad clutch coil. If the volt supply stops, you need to go backwards towards the source. Wiring diagram would be helpful at that point.

I agree with your thinking (see my last post). I'm going over to the barn now and do some measurements. Wish I had a wiring diagram -- working on that also.

 

[TripleR]

I'm a little slow at this A/C stuff but getting smarter (I think). I either read or someone told me most all A/C issues stem from low refrigerant. So I added a can (12 oz) and now realize that was the wrong thing to do w/o knowing for sure. I've blindly added R12 to older systems and R134 to newer cars and trucks and it always helped to improve the cooling. But, I may have screwed up this time and the only way of knowing for sure is to check the pressures. I'm off to Napa in the next hour to get a set of manifold gauges. I checked Harbour Freight and they have them but there are a lot of negative reviews.
I've put off buying a set for years but think I need them now. First, I'm going to check the voltage at the compressor and try to trace back.

I have a lot of mechanics in my family, so I have access to the equipment and just enough knowledge to get me in trouble, so if it's not really simple I take it to the shop.

I know some on here has said it's "simple", but suspect they are being modest as I have run into a lot of technicians who have been unable to fix these problems and just finished paying one only to have his "repair" last three days.

Good luck and keep us posted.

 

[Willl]

I checked Harbour Freight and they have them but there are a lot of negative reviews.

If you can get them to work right out of the box, they're OK.

 

[sunnyside360]

If you can get them to work right out of the box, they're OK.

Yea, it seems like either hit or miss with the HF gauges. I just picked up a manifold gauge set from Advance Auto for $89.99. They look to be well made -- 72" pressure hoses, solidly constructed valves and a nice storage case. Will check them out this afternoon.

 

[dstig1]

I know some on here has said it's "simple", but suspect they are being modest as I have run into a lot of technicians who have been unable to fix these problems and just finished paying one only to have his "repair" last three days.

That was me. I'm not a mechanic either. Once you get the hang of what makes an AC system tick, most problems are easily diagnosed. There just isn't much to them. It also helps to have had a Thermodynamics class somewhere in your past but frankly the logic is straightforward. The mental block most people have comes from needing a set of gages and a vacuum pump to be able to do anything on them, and that scares people off. The gage set is well worth the money as you can typically tell what is wrong right away with those. Even if you don't fix it yourself, you know where you stand. There are lots of resources on the web that can tell you what the problem is once you have a set of gage readings, the ambient temp and the cycle time of the clutch.

Sunnyside - It sounds like you've checked most of the obvious issues so far. So you are probably down to clutch gap wear or something electrical with a sensor or the coil. But you can't be sure (unless you find and fix the electrical issue..) without a gage set. Once you have a set, it becomes about the first thing you do - stick the gages on and see what's up...

-Dave

 

[sunnyside360]

Hooked up the new gauges and found the static pressure on both the high and low sides to be 125 psi. Then started the engine and set A/C control and blower on max but the compressor clutch would not engage during the half hour test. It's looking like the compressor clutch, low pressure cutout switch or wiring. All three fuses for the system are good. With 92 degree weather, very high humidity, hot engine and being soaking wet with sweat, I decided to do the electrical tests tomorrow. If no voltage at the compressor, I think the roof has to be removed for further testing. I did wiggle the electrical connector at the clutch in case of poor contact but no change.

 

[dstig1]

125 static sounds high unless the system was already hot or you live in the Mojave. Static system pressures tend to run near to the ambient temp in deg F. You had said you charged it up after the problem occured. It may well be overcharged now. That is a secondary issue at the moment, but should be addressed before putting it back into operation.

BTW a good test for the clutch gap is to put the AC on MAX (so you know it should be engaging) and then whack the clutch with a broom handle or screwdriver handle (like pushing it in). If it grabs even for a second or two, your clutch gap is too wide and the coil can't pull it in. Adjust the gap. If not you have other issues - start looking for voltage on the coil connector for one. Then you can jumper the LP and HP switch connectors to see if they are faulty.

 

[Willl]

125 static sounds high unless the system was already hot or you live in the Mojave.

He's not that far off with a 92 degree ambient.