A/C Diagnostic Help

[jmvar]

Hi guys, I have a 1995 cruiser that I recently (bit over a year ago) replaced all o-rings, condenser, drier after I found a leak at the condenser connection and the condenser.

This summer the system was working perfectly. The truck sat for 3 weeks while I was on vacation and when I came back the compressor wouldn't kick on.

Of course this is all happening as I move and all my tools, manuals, and manifold set are in boxes mid move.

I did some simple diagnosing and found that I am only getting 0.5V at the connection to the compressor when I turn the AC on tested with a multi meter. I thought it is probably one of the sensors.

Then just to test out the compressor I hard wired it to 12v and found that the clutch won't engage.

I will have access to my tools and manuals in about a week but I would like to start diagnosing where to go from here before then.

I hate to ask for a series of sensors that would limit voltage to the compressor but I don't have my service and electrical manual handy. Can someone help me out there? Also, what could cause the clutch not to engage when I apply 12v to the connector at the compressor? Could it be that I have failures at both ends?

Thanks

 

[excessive]

There are a ton of ac diagnostic process flow diagrams in the FSM from what I remember .

 

[Aloha Jen]

Just a guess, but your compressor clutch is probably bad if you cant get it to engage when you jump it.

 

[Landseer]

+1 for bad clutch

 

[Dave 2000]

+2

Regards

Dave

 

[jmvar]

I know this is simple but I am sleep deprived and stressed from a complicated move and house purchase/sale situation, and don't have any manuals on hand to reference.

Jumping the compressor is a simple as feeding it 12V from the battery? That is what I did and got nothing.

 

[SUMMIT CRUISERS]

I know this is simple but I am sleep deprived and stressed from a complicated move and house purchase/sale situation, and don't have any manuals on hand to reference.

Jumping the compressor is a simple as feeding it 12V from the battery? That is what I did and got nothing.

Yes and if no engagement clutch is bad. It's usually cheaper to buy the compressor and clutch together. I'm not even sure if a separate clutch can even be sourced today.

 

[Dave 2000]

The clutch needs a 12v positive only, the neg is the body. If working the clutch would engage whether system pressure is there or not.

I am wondering if something else fried when the clutch let go given the low output on your compressor power?

There is a sequence though, so a low gas would stop output going 12v soooooooo?

Regards

Dave

 

[shocktower]

You only get the .05 volts because the system, will not engage the clutch if there is a problem in the Freon or lack of oil, so I am thinking you system leaked again and you lost pressure

 

[jmvar]

So it sounds like I have a fried clutch and leaky compressor. Thanks guys, not really what I wanted to hear but I will confirm once I can get to my tools and manifold set to check pressure.

I will provide an update.

 

[Dave 2000]

The leak could be anywhere, it just seems coincidental you got the 0.5 volts and then nothing with 12v?

Regards

Dave

 

[RiverCityDave]

There is a front to back troubleshooting process included in the FSM, the first thing you should do is confirm pressure. Connect gauges, and see what's happening inside the lines. There are a few reasons the clutch won't engage if the pressure is low. The clutches are simple, and while they DO go bad, it isn't very common. The pressure switch (driver's side forward on the fender) is a more likely culprit. If it is not detecting pressure, either because there is none, or it is reading incorrectly, it will prevent the clutch from engaging.

Get the FSM out, hook up your gauges, and report back.

For the record, a reman Denso compressor including clutch is 178.00 at RockAuto.

 

[Dave 2000]

But if the OP had good 12v connections the clutch would engage regardles even if the pipes were disconnected.

Regards

Dave

 

[jmvar]

Can I check line pressures without getting the clutch to engage? Sorry, probably a dumb question again.

 

[Landseer]

You can check the pressures with the system off (compressor not running), it'll be a rough measurement but it'll tell you whether or not the system is empty.

Off the top of my head I wanna say the pressures should be around 80 PISG (both high and low) but don't quote me on that. If they're under 20 PSIG then most of the refrigerant has leaked out.

 

[jmvar]

Thanks for all the replies and all of the help. Yesterday I managed to sneak away and unbox some tools from my move including the manifold set. Taking the pressures was easy....0 psi across the board. I ripped out the compressor and the evaporator since they are the only 2 components left in the AC system that are original and I will be replacing them along with the drier and expansion valve.