V5 compressor swap in '97 Chevrolet Monte Carlo

[Aren Cambre]

Hello. It is great to see this upgraded bulletin board. A few years ago you guys were helpful with a few questions I had on my ’74 Chevrolet Nova’s conversion from R-12 & VIR w/POA & TXV to R-134a/FOT . I lost that Nova to a nasty freak accident in 2004 and inherited the wife’s 1997 Chevrolet Monte Carlo, which now has 134,000 miles and a broken A/C. So now I have more relevant, up to date questions.

Towards the end of Dallas’s 2006 A/C season, the compressor got so loud that I heard it below 25 mph. So I know I need to replace the compressor.

This spring, when it was time to use the A/C again, I couldn’t get the compressor to engage. My low pressure switch, which is just behind the accumulator, has 3 wires: gray, black, and red (or red stripe?). I jumped the red and gray with a paper clip and flipped on the A/C with the car running, but I still didn’t get compressor action. Looking at the front of the compressor, the clutch obviously isn’t engaging, and there is no cooling. I got out a trouble light, and I do get voltage on the gray wire.

Is there something else to check, or may I have an electrical failure?

Since I already know the compressor is bad, I have to replace that, too. So speaking of the replacement, I would appreciate your thoughts on the following:

• I plan to use PAG 150 oil, and I will measure whatever comes out of the parts I take out and add that same amount when I reinstall.
• If the oil is clean, I am not going to worry about flushing the entire system. But if the oil is dirty, I will have to take it all apart and flush the entire system.
• If I end up flushing out the entire system, how much PAG 150 do I need to add to the system to make it right?
• If I need to flush, is it OK to just pour denatured alcohol in the evaporator and condensor and blow it out with compressed air and repeat until I get no more crud? Do I need to use the flush formulas?
• I will minimize exposure of the PAG oil and the insides of the compressor and accumulator and everything else to air to prevent absorption of water. (I recall that PAG is pretty hydroscopic?)
• If the diagnosis of the compressor failure above turns out to be due to a leak, I plan to use UV dye. I already have a 1 foot fluorescent UV light. How do I detect the leakage? Does it show up as a spray pattern around the leak?
• How do I replace the orifice tube? I assume I just remove the accumulator and it will be pretty close to it?
• Should I bother with a VOV or stick with a stock orifice tube? I recall Nacho speaking poorly of some kind of variable OT, but I don’t remember if he was talking about a specific kind of all of them.
• Since this car has 134K miles and 10 years, should I throw on a new hose assembly? The linked assembly only works between the compressor and the accumulator and orifice tube. Is there another hose assembly for the rear part of the engine bay, between the OT and accumulator and the evaporator?
• I have a Robinair 5 CFM vacuum pump. After I verify no leaks, I plan to run it for 1 hour. Is that a good idea?
• Generally, how much torque do I apply to the fittings?

Thanks in advance for your help!

Aren Cambre

[GM Tech]

V-5 compressors get noisy when they get low on charge- your "known" bad compressor may be quiet when it has the right amount of refrigerant in it-- How much is in your system? What is the static pressure? - I'll bet it is below 40 psi since the 3-wire pressure transducer is not allowing the compressor to engage- "to save" the compressor-- so if you add some charge and some dye- most likely your compressor will come on and start cooling-- but don't stop there- find and fix your leak- your system does not go flat for no reason- no one is stealing your refrigerant-- 65% of all a/c system failures are due to loss of refrigerant- and I'll bet you have little or none in your system.

BTW don't "jumper" 3-wire "switches" its a good way to fry an ECM- your system is not designed that way anymore..........

[Aren Cambre]

V-5 compressors get noisy when they get low on charge- your "known" bad compressor may be quiet when it has the right amount of refrigerant in it-- How much is in your system? What is the static pressure? - I'll bet it is below 40 psi since the 3-wire pressure transducer is not allowing the compressor to engage- "to save" the compressor-- so if you add some charge and some dye- most likely your compressor will come on and start cooling-- but don't stop there- find and fix your leak- your system does not go flat for no reason- no one is stealing your refrigerant-- 65% of all a/c system failures are due to loss of refrigerant- and I'll bet you have little or none in your system.

BTW don't "jumper" 3-wire "switches" its a good way to fry an ECM- your system is not designed that way anymore..........

OK, thanks. Advice noted. Before I go further, I will try adding refrigerant and dye and see what happens.

[Aren Cambre]

V-5 compressors get noisy when they get low on charge- your "known" bad compressor may be quiet when it has the right amount of refrigerant in it-- How much is in your system? What is the static pressure? - I'll bet it is below 40 psi since the 3-wire pressure transducer is not allowing the compressor to engage- "to save" the compressor-- so if you add some charge and some dye- most likely your compressor will come on and start cooling-- but don't stop there- find and fix your leak- your system does not go flat for no reason- no one is stealing your refrigerant-- 65% of all a/c system failures are due to loss of refrigerant- and I'll bet you have little or none in your system.

OK, I got a gauge set hooked up. The static pressure was about 8 PSI, so we're in definite leak territory.

I introduced enough of a 12 oz can of R-134a into the system to get 63 PSI static. I still got no compressor action.

If I run the engine and turn the A/C control from a non-compressor mode to a compressor mode (e.g., vent to bilevel), the engine surges about 100-150 RPM and the radiator fans kick on. So it seems like the car thinks the compressor should be turning on. When I turn the switch back to vent, the RPMs drop back to the baseline, but the fans stay on. The engine temp is well under operating temps at this point, but for all I know the computer could be programmed to keep the fans on a bit after the compressor disengages to bleed off more heat? If I turn it back to bilevel at that point, the engine surges again. I can repeat this at will.

Part of me is leaning towards an electrical problem, but another part wonders if the compressor is just refusing to engage. The compressor is definitely not spinning--not making any noise, and the center part of the pulley is staying still.

Stupid me found that page 12-40 of my Haynes manual is the A/C wiring diagram for my car. (Don't know how I missed that earlier.) It appears that a light green wire carries the A/C (compressor) request signal from the dash box to the PCM. Because of the RPM surge and the fans coming on, it seems like the PCM is properly signaling the compressor request, but somehow it's not getting to the compressor.

I guess the next thing to do at this point is to see if a signal is actually sent to the compressor?

By the way, I noticed my low side fitting didn't have a cap! Wouldn't it be nice if that ends up being the problem? (And the probability that is really the problem is probably "slim to none." )

[Hal]

Recover the refrigerant, pull a deep vacuum and recharge the system (liquid thru the low side) then start the AC. The compressor should start, but you will still have to fix the leak. As GM tech stated, the compressor shaft seal is suspect. The way you added, means you probably have more air than refrigerant in the system. Only way is start from a vacuum
hal

[Aren Cambre]

Recover the refrigerant, pull a deep vacuum and recharge the system (liquid thru the low side) then start the AC. The compressor should start, but you will still have to fix the leak. As GM tech stated, the compressor shaft seal is suspect. The way you added, means you probably have more air than refrigerant in the system. Only way is start from a vacuum
hal

Hal, thanks.

Turns out that the wiring right at the compressor is suspect. I did a few electrical tests and eventually figured out that there is a bad connection at the compressor. I fixed that connection "well enough" for now, but I will need to do a better fix later. Spraying both ends of the connector with carburetor cleaner seems to have helped, but it will still sometimes cut on and off. I can always make it cut back on when I finagle the connection with a pry bar.

As for the system, I did a 3 second spray of that UV dye and then introduced about 1.75 12 oz cans of R-134a into the system. I ran the A/C for 2-4 minutes twice. The ambient is about 82-84. Bumping up the RPMs a bit, and with the A/C on MAX, I get 27 PSI low/210 PSI high. (Well, the high goes closer to 250 at some point, but the fans kick into "wild crazy fast mode", and that brings the high down to 210.) Vent temps are definitely showing cooling but aren't that impressive. (I didn't run it long enough after I put the probe in to really know where the temps ended up.)

Static pressure is about 83 PSI.

I agree with you about the vacuum. I first want to run the system a bit and see where the dye ends up. If I see no dye, I'll go ahead and vacuum and reintroduce about 30 oz of refrigerant.

By the way, GM Tech is probably correct. The compressor is not that loud right now.

Aren

[Aren Cambre]

Drove to work this morning. Ambient was about 73, dash temp reading got down to 56 on fresh air mode with fan speed on 2 of 4 (where 4 is highest). I'll check for leaks again tonight with UV light.

If I find some, I'll fix leak ASAP. If I don't find leaks, I'll vacuum, do leak test, and do proper 30 oz charge.

[Tom Greenleaf]

That is poor performance while driving with low fan and 73F ambient indicating a problem still exists. Even if done recently check pressures again and fix any leaks,

T

[Aren Cambre]

That is poor performance while driving with low fan and 73F ambient indicating a problem still exists. Even if done recently check pressures again and fix any leaks,

T

I got 46 degrees on the way home with A/C on recirc. Ambient was around 84.

I was going to pull a vacuum tonight, but found my Robinair pump is way low on oil. (It was recently relocated, and oil leaked out during the move.) So I have to track down a vendor for this oil. It may be a few more days before I post anything meaningful to this thread, but I'll still be watching for comments.

Aren

[Tom Greenleaf]

Much better #s this time and temps. Said elsewhere the pump oil is at the store here,

T

[Aren Cambre]

I may have found my leak. The system ran OK on Monday, Tuesday, and Wednesday. Then Thursday the compressor won't even come on.

Looked at the system and notice something weird with the high side service port cap. Turns out the cap is broken in two with the nub stuck in the valve. Dye was all over the inside of the cap and some on the port itself.

I did a soapy water test and got a clear positive.

I hooked up a gauge to the high port and got a hair above 0 PSI.

I am guessing the service cap was minimizing the leak but must have broken on Wednesday, allowing refrigerant to escape much more quickly.

Now for the question: there is some rubber piece that prevents me from getting access to the Schrader valve. Go to my blog entry about this and see the 3rd and 4th pictures for closeups of the port. Do I need to wrench the port open to get access to this valve?

[GM Tech]

believe it or not the plastic cap is the primary seal- bubbling from the schrader valve can occur- and they are not designed to seal off 100%- that is why the cap has the rubber element inside- to seal the system tight-- you need a new cap...........

[Aren Cambre]

believe it or not the plastic cap is the primary seal- bubbling from the schrader valve can occur- and they are not designed to seal off 100%- that is why the cap has the rubber element inside- to seal the system tight-- you need a new cap...........

Wow, I noticed that the caps I got from AutoZone had no rubber seal! It was part of a $5 kit. I guess I will return that stupid kit.

Would you call this excessive bubbling, though?


The bubbles were "used up" within about 10-15 seconds. Seems kind of fast to me. But I trust your judgment.

[Tom Greenleaf]

That's way too fast. While you are empty consider just replacing the whole thing. That ball valve really can't be serviced. Good caps will work but I don't like to rely just on the cap,

T

[Aren Cambre]

That's way too fast. While you are empty consider just replacing the whole thing. That ball valve really can't be serviced. Good caps will work but I don't like to rely just on the cap,

I need to unscrew that fitting to get access to the valve, right? Inside, is it just a standard Schrader valve?

[Tom Greenleaf]

I just looked at a whole bunch of them in my shop and none looked exactly identical to yours. My OE 97 Chev Truck uses a regular hex wrench and would come apart. Others had real shraders inside them and they were high side acme fittings. Yours looks like just the base is a hex and another looks like an eight sided job.

I don't know if the threads under that would be universally received. Your ball seal is like my truck which looks like the threads would have to make the seal there also and another used an O ring. There may be an issue with sealing the threads to keep this headache alive and use of teflon tape should work but the last thing you want is a thread of that like white hair to mess up the show all over again. A dealer might have the exact one you have and I really don't know. I do know they are very sticky to remove and it's like threadlock was used on some I've removed. My OE cap is plenty strong enough with seal inside it to seal it off with no leak. Perhaps that would be the easiest thing to do -- replace the cap with a new OE one.

Now with refrgerant loss there is a question of air in the system. A pound or two of pressure is certainly empty and when vehicle is cold it may be in a slight vacuum and need to be re vacuumed out.

It's aweful that such a stupid thing is such a headache,

T

[Warren Willingham]

Almost all GM vehicles used the primary seal on the high side. Is yours the high side? I'll ask because it saves reading time. This is a long thread. GMTech is right, as usual. I haven't seen any of our caps come without the small thick black oring inside. If your primary seal is leaking and you are going to have the system down, change it. Here's what they look like.http://www.acsource.com/index.asp?PageAction=PRODSEARCH&txtSearch=primary+&btnSearch=GO&Page=1
You could get by with a good cap b ut____ These valves usd to run large dollars at the dealers. Most box stores didn't know what they were, and still might not, but dealers might have come down. If not you have the link. Seeya.

[Aren Cambre]

Almost all GM vehicles used the primary seal on the high side. Is yours the high side? I'll ask because it saves reading time. This is a long thread. GMTech is right, as usual. I haven't seen any of our caps come without the small thick black oring inside. If your primary seal is leaking and you are going to have the system down, change it. Here's what they look like.http://www.acsource.com/index.asp?PageAction=PRODSEARCH&txtSearch=primary+&btnSearch=GO&Page=1
You could get by with a good cap b ut____ These valves usd to run large dollars at the dealers. Most box stores didn't know what they were, and still might not, but dealers might have come down. If not you have the link. Seeya.

Yes, this problem valve is on the high side. This is a '97 Chevrolet Monte Carlo; which of the two GM valves on that page would be the right replacement valve? Do you sell a valve that comes with the cap?

Aren

[Pavlograd]

I'm on a 1996 Chev Lumina 3.1 sedan. Is the orifice tube located inside the line at the entrance to the dryer? I don't want to crack that fitting unless I'm sure. Also, I'm installing a used (junk yard) compressor. Can I just pull a vacuum (renting a vacuum pump) for 45 minutes, and then inject new refrigerant in on the low side? How much does it take - 3 lbs? I don't know how to work those double gauges.
Is there a website that explains this process anywhere?

Thanks, Steve

[Tom Greenleaf]

Please repost with your own new thread as you are at the bottom of another.

Please state just what has happened that you need a new (used) compressor and we can help you more. BTW 96 Lumina lists 30oz on a chart I have not 3lbs but go by any sticker underhood as 3lbs = 48oz which would blow up the system if that far off,

T