chandler1981

Hey everyone, and thanks in advance if you can help me. I am working on a 2003 Tahoe with Auto Climate Control. The compressor will not come on by itself. The system is charged. I can jump the compressor on at the AC comp relay and it engages. But it will not engage if I jump from Low Side Press Switch Wires.

I am about to hook up my manifold gages to see what the pressures are. Can anyone think of any tests that would be useful? AC will not cool. If I jump compressor at relay, the vent temp is still 80 deg F when Auto Climate Control is on 60, 65 etc.

73shark

Welcome to the forum.

If you haven't checked the pressures yet, how do you know it's charged?

chandler1981

Shark, Thanks for the reply. I was told that by the owner of the vehicle, but I should of known better.

I hooked up my gauges and found some very wierd readings. Static pressures are about 10 psi. It will leak down to 2 psi in about 5 mins and the service hoses from gauges are tight. I added 12 oz of 134a to the system and cheecked it again.

When I added the can of freon, I didn't engage the compressor and the high and low pressures rose to around 35 psi before the can was empty. Sure enough, the pressure leaked back down close to zero psi within the matter of minutes.

I checked the readings with the compressor jumped across the relay and the low side actually went into a vacuum (negative) reading. The high side was only about 50 psi.

I don't see any leaks but it seems to me that there has to be a sizeable leak for the pressures to leak down that quickly. Any chance the evaporator is leaking? Nothing inside the pass floorboard but I added some dye to the system and will use my blacklight this evening to check.

What would cause the low side to be in a vacuum and the high side to only have 45-50 psi? Could it be this empty? I wander if the orifice tube is restricted?



I have a pump to vacuum the system but I can't imagine that it will hold. Should I even try this yet or is there obviously a leak present?

Thanks to anyone willing to help.

73shark

Static pressure w/ system off should be in the neighborhood of 120 psi. Appears that you have a massive leak somewhere.

LARIDERS

not sure on the 03 but my 99 had a bad leak and took a while to find. it was in the rear a/c line going to the back. seem on the pass. side back wheele inside was the a/c line and all the years it was hitting on the frame it rest on and had lots of little pin size hole in it. you could try leak finder stuff with a black light.

chandler1981

just out of curiosity, i pulled a vacuum for about 5 mins and then closed off the gauges. it didn't even hold for 5 mins. It immediately began leaking down and didn't stop until the gauges were back to zero. I am going to look even closer with my blacklight. I ran some dye thru the sysem and a quick inspection regarded nothing. I will look closely at all lines, connections, and components. I think it will be easy to spot considering how quickly the pressure / vacuum leaks down. If anybody has any suggestions, I would appreciate it.

I hope I don't have to waste any more freon or dye until I recharge the system. I feel that with a leak this big it will be easy to spot once I finally locate it. Thanks again to all who have helped.

Thumper_ehhhhh

alot of shops run a dye in the lines to find the leak. Most of the time its just bad oring seals.

73shark

You can buy a can of r134a w/ a leak detector dye in it.

chandler1981

I put a can of 134a with dye in it the other day.

Ok... So.. I got out the big blacklight (an old one I had in the attic from my younger days) and there appears to be dye everywhere! It is mostly on the cooling system?? It is all over the radiator hoses, heater hoses, water pump, and even on some of the pulleys. Its also all over the undercarriage of the tahoe. My guess is that the fan is blowing it everywhere. The wierd thing is that it is spread evenly everywhere. Its hard to see the condenser with the grille and the fan shroud in the way so i will remove them the see better. I will also remove the skid plate to see compresssor area better. One suspect place seems to be where the hoses meet at the compressor. I don't know exactly what its called but its an aluminum block leaving the compressor where the high press hoses meet.

Also, The passengers side frame rail is covered, and the control arm, tie rod, etc. There is no dye on the a/c hoses themselves though.

Any ideas? The interior looks like it has dye on it too but I think it might be where someone has dyed the carpets, cleaned the interior, etc. Its not my vehicle so I don't know the history of the vehicle. I do know that it is a good friend of my wifes car, and she lived in Wyoming for 2 yrs. One summer everthing was fine, the next...well.. the air didn't work.

Thumper_ehhhhh

You could be onto something. Hole in a/c rad and the fan spread it like wildfire.