AC Diagnostic Help

With all this, did you trick the clutch into staying engaged? Or was it still cycling off after a sec? If it stayed running and your pressures stayed around 100 on both sides, it sounds like your compressor isn't compressing. That pressure is in the realm of "right" on an equalized system (i.e. compressor off) although if you have a fresh can you should be able to (not that you should do it, mind you, just that it should be physically possible) get more R134 in... although once the can pressure equalizes with the low side pressure you're not going to get any more to go in, so if this was the same can you used 3/4 of, and your low side pressure is 3x what it should be, that doesn't mean much.

 

At first, I just tried "tricking" the compressor by continually re-pressing the AC button. It would engage and run for just a second or two. That's how 3/4 of a can entered the system and pressures read as stated.

Then I "forced" the compressor clutch to turn on (with my 12v switch) and run in hope of drawing more in, but nothing happened. No more coolant through the site glass and the pressure did not change. I only left the switch on for 10 or so seconds.

 

You can replace your relay with a couple jumpers , push the AC button to make the compressor stay on . I did this just to make sure my compressor was good on mine

 

That makes sense.. but I just ran a switch from the battery so I could turn it on and off. Not sure if that's better or worse...

 

I'm not a great A/C expert, especially through a screen, but if you had the clutch engaged, and the pressures stayed equalized, that'd be enough to condemn a compressor for me... you should see SOMETHING move on the gauges if the shaft is spinning.

I'll give you the same caveat I usually do- I can't say that nothing else is wrong, but I can pretty confidently say that is wrong, and diagnosis can't continue until you know it's right. Unfortunately it sounds like an internal failure, and I think you've got a decent chance of finding shiny chunks all up in there, meaning you also need a condenser, drier, and a couple cans of Kooler Klean to flush the lines, if you choose to try to DIY.

 

I assume these chunks would get pulled into a new compressor and destroy it?

Would the proper steps be...

• Remove old compressor
• Remove old condenser
• Flush the lines
• Install new compressor / condensor

Or... does one have to take the dash apart as well and clean out lines connected to all the fancy bits under there?

 

I wanna say there should be some kinda prefilter thing in the liquid line that runs from the condenser to the expansion valve & evaporator... not 100% on that as it's not entirely standard and I've never had to mess with A/C on a 2nd gen.

If I'm right... replace that, flush the liquid line towards the condenser end while it's apart, flush the discharge line (compressor to condenser, so you'll have both ends off anyway) and might as well flush the suction line from the evaporator back to the compressor, although in theory it shouldn't have anything in it.

Pretty well have to replace the condenser if it's contaminated. In the old days they were like the coils on the back of your fridge, or a generic trans cooler- one line or a couple lines running back and forth between the inlet and outlet, called a serpentine condenser. Years ago pretty much everyone switched to parallel flow, the inlet is on one side and the outlet is on the other with header "tanks" running vertically, and what you see between the rows of fins is a little strip with 4-6 little tubes, like the insulation of a 4-wire trailer wire without the wire inside. When you try to flush one you'll get some out, but then the flush solvent will just take the path of least resistance and you end up with 2/3 of the rows with crap still in them.

 

You can't tell anything from the compressor running momentarily. Sorry, but you should take it to someone that knows AC.

 

I can make the compressor run continually with the switch. No pressure change or R134 taken in.

I am trying to learn how to be somebody who knows AC... that's why I post here

 

I had the flashing light. Tested everything and it turned out to be the ground on the ac compressor.

 

If it is running continuously the compressor is not pumping or the clutch is slipping and not turning the compressor. The latter will make the AC light blink. How many ounces of freon is in the system now?

 

About 3/4 of a can 12oz can went in.

However, I tried it with the pressure switch connected and then jumped. In my head, once the pressure switch is jumped the compressor would stay on with the AC switch engaged but it does not... light just blinks.

I can use the secondary switch to "force" the compressor to come on and stay on as long as I like, but even with it running there is no change is PSI, no more R134 goes in. There is no noise from the compressor and the clutch appears to be spinning smoothly... no jumps or belt squeal (when the bypass switch is on)

 

The system was empty but would only take 3/4 of a can, is that correct?

 

Correct.... and the HI/LO pressure basically equalized (100/95) and no more R134 could be seen through the site glass

This was with the compressor being "forced" to run

 

If you are sure the clutch is engaging and the compressor is turning, the compressor is toast. It's not pumping at all.

 

I think thats where HVAC school would come in

 

Getting closer...

Removed old compressor. It just spins with zero resistance. New compressor "compresses" when turning by hand.

Added oil, installed new compressor. System took the R134 and started blowing cold air.

However...

At idle, AC slowly starts to warm until it's basically warm. Driving immediately cools back off. AC works great while driving all the time.

It's very possible I put in to much or to little R134... but I would guess I am within an ounce of required.

Maybe a problem with the condenser? Clogged?

To much or to little R134?

Oil level issue?

Thanks for any guesses...

 

Check your fan clutch. Air flow problem. If the condenser/radiator is dirty/plugged up, driving wouldn't help. But in never hurts to wash them out.
Are you sure you added 21oz of freon? Also how much oil did you add? Did you drain oil from the old compressor and add that amount to the new one?
Edit: Did you put in a new condenser?

 

Are you referring to the main fan/clutch? Behind the radiator? If that was failing/operating poorly... wouldn't engine temps also rise?

If the condenser was clogged or dirty... might driving air flow be enough to make it work... but fan at idle just doesn't move enough air?

My best attempt to add 21oz yes... but towards the end of the second can things got confused. So... might be an ounce more or less (sorry that answer is not very specific)

The old compressor was blown out. I didn't feel measuring oil from it or re-using it would be wise.

The FSM stated 150cc for a new compressor so that's what I put in my empty new compressor.

 

You could still be a little undercharged. Really need a proper a/c service machine to get the charge amount correct

Also a word of warning, compressors usually fail because of lack of lubrication. The compressor oil can leave the system through a refrigerant leak. In order to protect your new compressor, make sure there isnt a leak somewhere else in the system