Help

[TurboDiverArt]

Hi All,

Discovered today that the A/C on my 1999 Suburban is not working. I

[DaveNY]

Hi Art
I think I would start from the beginning and check the plug on the compressor for voltage, then check low pressure switch for voltage in and out. If the clutch is getting power and does not engage you have another clutch prob. if the switch on the low side has no voltage out the you have a bad switch or no freon. There is a cheap gauge to check the freon sort of a glorified tire gauge, available almost anywhere. If you have freon and no voltage out of the low pressure switch then jump the switch (dont jump the switch without freon in the system can damage comp) If you find low freon, your unit should have 134a and a recharge kit it available any where. But it is a sealed system and it has a leak if it requires a charge. Good Luck Dave

[TurboDiverArt]

Hi Art
I think I would start from the beginning and check the plug on the compressor for voltage, then check low pressure switch for voltage in and out. If the clutch is getting power and does not engage you have another clutch prob. if the switch on the low side has no voltage out the you have a bad switch or no freon. There is a cheap gauge to check the freon sort of a glorified tire gauge, available almost anywhere. If you have freon and no voltage out of the low pressure switch then jump the switch (dont jump the switch without freon in the system can damage comp) If you find low freon, your unit should have 134a and a recharge kit it available any where. But it is a sealed system and it has a leak if it requires a charge. Good Luck Dave
Thanks Dave!

I assume the two wires on the compressor are a power and ground?

On the pressure switch, do you know which wire is the hot in and which is the hot out? I assume that disconnected and the A/C on I should see hot to one side the whole time? The other would be the hot out?

Thanks for all the help!
Art.

[HammerWerf]

Art,

I was looking at the compressor on my 99 suburban a couple of weeks ago, And I noticed an increase in the greasy-dirt buildup on it. Suspecting it was leaking, I took it to my mechanic, who said, it's leaking past the O-rings that seal the end bells of the units. I still have some A/C, but it is getting warmer. Replacement will be soon. Summer in the desert-SW in a dark blue suburban = unhappy wife and kids. She says fix it.

What I found was the oily dirt was only between the endbells.

I also saw the condensor high pressure connection with the flex hose also appears to be leaking at the hose crimp. Good ol' weatherhead crimp GM is so fond of. Need to look at that more closely. The shape of the hose may be adding pressure to the joint that may need to be releived at repair time. Looks kinda like a twisted " S ".

These are my observations. Hope they prove useful.

HammerWerf

[TurboDiverArt]

Art,

I was looking at the compressor on my 99 suburban a couple of weeks ago, And I noticed an increase in the greasy-dirt buildup on it. Suspecting it was leaking, I took it to my mechanic, who said, it's leaking past the O-rings that seal the end bells of the units. I still have some A/C, but it is getting warmer. Replacement will be soon. Summer in the desert-SW in a dark blue suburban = unhappy wife and kids. She says fix it.

What I found was the oily dirt was only between the endbells.

I also saw the condensor high pressure connection with the flex hose also appears to be leaking at the hose crimp. Good ol' weatherhead crimp GM is so fond of. Need to look at that more closely. The shape of the hose may be adding pressure to the joint that may need to be releived at repair time. Looks kinda like a twisted " S ".

These are my observations. Hope they prove useful.

HammerWerf
Thanks for the info, I'll check it out on mine. I'm going to check a few electrical connections on mine to try and point me in the right direction. If I have to replace the pressure switch I think the system needs to be evacuated so I might as well bring it to a place that can scavenge the system and only charge me for the excess I may need.

It's still mostly cool in New Jersey so I'm pretty lucky but needs to be fixed. I agree, hot car does not equal happy family!

Art.

[BobND]

Almost certainly, the pressure switch sits on a "Schrader valve" that will close off when you unscrew the pressure switch, so you can change it out with almost no loss of refrigerant. It will leak a bit as you unscrew it, but then seal off before the end of the threads are reached.

(On older units, at least up to 1994, the pressure switch carried the actual current to operate the AC clutch. I seem to recall at some point the pressure switch setup was changed so it simply provided a signal to a logic circuit, likely in the climate control "control head", where the actual switching was done. I don't know if that applies to your vehicle, but keep that possibility it in mind as you are troubleshooting.)

[ZZ]

Over the years, my experience has been with older compressors that the seals leak especially over the winter months. I've had several vehicles with good A/C all Summer just to find out come Spring that the Freon would be gone. I'd pull a vacuum and recharge them and then go all summer again. The seals stay more pliable when they're used everyday or two.

It took serveral years for me to figure out why the car makers wired the compressor to run on bi-level & defrost. They did this for two reasons. One was to defog all of the windows and to give the system some exercise through the cold months. Like a goose; I used to unplug mine every Fall, and pull the belt if it was the only thing that it ran.

[TurboDiverArt]

OK, I finally got a chance to get out and look at the truck. Here

[BobND]

I kind of figured the pressure switch switched a control curcuit only on a newer unit like your's.

I dealt with a similar problem a couple of years ago, on a pickup a couple of years older than your Sub, and we had to replace the climate control "head".

Just to double check, look to see if there may be another pressure switch near the condensor, or in the compressor, in addition to the one you have already found.

[TurboDiverArt]

I kind of figured the pressure switch switched a control curcuit only on a newer unit like your's.

I dealt with a similar problem a couple of years ago, on a pickup a couple of years older than your Sub, and we had to replace the climate control "head".

Just to double check, look to see if there may be another pressure switch near the condensor, or in the compressor, in addition to the one you have already found.
Good call Bob! I checked the pressure switch at the condenser and it's not feeding a power signal. With the truck off, the light green wire appears to ground. When I start the truck with the AC on the light green wire sees 12V. I checked and the dark green wire is not getting any voltage and is not a ground. I tried jumpering the two wires and the compressor clutch engages. Did it only for a second.

So, I think this might narrow it down to either a bad condenser pressure switch or low Freon. I don't have a gauge that fits an R-134 shradder valve. I have an R-12 gauge but it doesn't seem to screw on. I guess my choices are to either go with my gut and get a new pressure switch and try it out or to buy an R-134 gauge and check the pressure. I have a feeling that the switch and gauge are probably about the same price.

There is a switch on the back of the condenser but I haven

[BobND]

If you don't want to make an investment in R-134 AC tools at this time, pick up a cheap recharge kit that has a pressure guage built into the fittings.

[TurboDiverArt]

If you don't want to make an investment in R-134 AC tools at this time, pick up a cheap recharge kit that has a pressure guage built into the fittings.
Yeah, I did notice them at NAPA when I was trying to get a new high-pressure switch. They didn't have one up front and the warehouse was closed. I'm going to have to go tomorrow to pick up the switch.

Art.

[DmaxMaverick]

Walmart has A/C "service/repair" kits. I've used the kits with an R134 can, gauge, fitting, and includes oil and stop leak. I used one on my 2000 Impala at the beginning of last summer, and it's still up and working. The kit was about $10.