A/C System Problem - no cold, diagnostic indicates Air Mix circuit

[Joshs]

I'm having an issue with my A/C system, and I'm thinking may be the control board. If so I'll be sending it in to BrianK. But first I need to make sure that it's the (or at least -A-) problem.

The A/C won't blow cold. As far as I can tell, all the fans and other components are working ok, although I haven't done a thorough investigation of all parts. I had the ac retrofitted by Autowave with 134a (or whatever it is) 2 years ago when I bought the car. It worked great for a while, although I did have cold water come out of the inner vents a couple times. However a couple months ago the system stopped blowing cold. Driving home from the Mohave last week was enough to motivate me to try to fix it.

The circuit-check diagnostic mode indicates the air mix control motor is 'bad'.

Running through the troubleshooting tree on 22-26 of the service manual, when checking for 'battery voltage', I only see about 4.5v, but it jumps around a bit as I turn the temp dial. Is there supposed to be a constant 12-13v between #15 and gnd or #1 and gnd, when turning the dial?

Running through the rest of the steps, continuity seems fine. I didn't test the air mix control motor as described on 22-90, but perhaps I should? When I put the system in auto-cycle mode I can see the motor move into 3 different positions, moving the pull cable attached to the motor. So it moves, but I suppose it's possible that it's not sending the proper signal back to the CCU. It looks like there's even a small nick on one of the wires that feed the air mix control motor- into the insulation but the wire doesn't appear severed.. I'll tape it up to prevent shorting, but if there's already an indication that the CCU is bad then there's probably no need to replace that section of wire just yet, since continuity is fine.

Thanks for any help you can give!

-Josh

 

[NSXHan]

I doubt you're problem was the same as ICR8NRG's but his was just both fuses being blown. You may want to PM D' Ecosse as it seems he knows quite a bit about A/C imo. Sorry I have no better information to put forth onto the table. Good Luck.

 

[Daedalus]

Is the compressor kicking on when you turn on the AC?

 

[Briank]

A lot of CCU's I see have problems with moving the mix motor but yours seems th be working but there may be a problem in the feed back signal to the CCU. Either its not there or the ccu is not seeing it. Not having the feed back signal will not stop it from moving so you should still have cooling. The question above is a good one, is your compressor running? If not them you may need to get the Freon refiled.

 

[Joshs]

A lot of CCU's I see have problems with moving the mix motor but yours seems th be working but there may be a problem in the feed back signal to the CCU. Either its not there or the ccu is not seeing it. Not having the feed back signal will not stop it from moving so you should still have cooling. The question above is a good one, is your compressor running? If not them you may need to get the Freon refiled.

I located the compressor, but I'm not sure how to tell if it's running. With the car started, the engine does seem to go under some load (and idle change) when I turn on the blower. The belt going to the idler pulley and compressor is turning, but I can't discern any differences with the a/c on or off. So I'm not sure if the compressor clutch is engaging or not. Is there a clear indicator?

Also, where is the sight glass for looking for bubbles in the coolant? I can't seem to discover it's location in the manual.

Thanks for the help!

-Josh

 

[Briank]

The window is on the receiver dryer up front by the windshield washer fluid tank. If you look at the compressor when it’s on the whole pulley will be turning when it’s on and when off just the outside edge will be turning. Hearing the engine take some load could just be the electrical load on the alternator of the blower and condenser fans running.

 

[Hugh]

Also, where is the sight glass for looking for bubbles in the coolant? I can't seem to discover it's location in the manual.

Open your hood, stand in front of the car and look straight down. It's just forward of the latch mechanism on top of the receiver/dryer.

 

[Joshs]

The window is on the receiver dryer up front by the windshield washer fluid tank. If you look at the compressor when it’s on the whole pulley will be turning when it’s on and when off just the outside edge will be turning. Hearing the engine take some load could just be the electrical load on the alternator of the blower and condenser fans running.

Thanks for the details. Now that I know what to look for, I can see that the 'pressure plate' (22-76) does not spin with the a/c on. So the compressor clutch isn't engaging. Time to follow the a/c compressor troublshooting on 22-56 to see if it's a fuse or relay..

-Josh

 

[Joshs]

Open your hood, stand in front of the car and look straight down. It's just forward of the latch mechanism on top of the receiver/dryer.

I see it now but there doesn't seem to be much going on. It's possible that there is a super tiny bubble in there but it's difficult to tell. Certainly no bubblng, although I haven't tried running the a/c and watching the window for an extended period of time.

The 2 fuses check out ok, maybe its a relay..

-Josh

 

[Daedalus]

The sightglass won't be of much value if the compressor isn't engaging. The quick way to check for low freon is to check continuity at the pressure switch.

 

[Joshs]

The sightglass won't be of much value if the compressor isn't engaging. The quick way to check for low freon is to check continuity at the pressure switch.

I found the triple pressure switch, but it 'points' downward and i don't see how I can get my probes in there to obtain a reading. Is there a good location to check it from?

I tested the compressor relay and it checked out fine.

-Josh

 

[D'Ecosse]

I found the triple pressure switch, but it 'points' downward and i don't see how I can get my probes in there to obtain a reading. Is there a good location to check it from?

I tested the compressor relay and it checked out fine.

-Josh

Easier to just short the connector & see if compressor then runs - if it does start to run then your freon is low. Short between the BRN/BLK & BLK or alternatively just short the BRN/BLK to ground. If it runs, don't leave it running - it is purposely disabled if not enough freon to activate.
Be sure to have 'demand' for cooling when you test it.

 

[Joshs]

Easier to just short the connector & see if compressor then runs - if it does start to run then your freon is low. Short between the BRN/BLK & BLK or alternatively just short the BRN/BLK to ground. If it runs, don't leave it running - it is purposely disabled if not enough freon to activate.
Be sure to have 'demand' for cooling when you test it.

Thanks for the tip - I shorted the pins on the connector and sure enough, the compressor started running!

I guess my 134a is low/gone, which means I probably have a leak somewhere, since it was just charged 24 months ago. Darn, I was kinda hoping it was just the CCU since that's an easy drop in fix. Locating and fixing the leak is beyond my current abilities!

Now I must either try to find a good A/C place nearby (west-LA), or maybe it's worth the extra effort to take it down to Autowave? Anyone have a reccomendation?

Thanks for all the help everyone!

-Josh

 

[Daedalus]

I have a sniffer if you want to borrow it, though it may not make fixing it any cheaper. You could just top off to keep you cool in the near-term till you get it fixed. Trace the lines around the compressor and around the condenser as much as possible. Usually the source of the leak will be grimy/oily from dirt building up on the oil that has leaked out. Often leaks happen at the unions.
Where you get it repaired will depend on where the leak is. If it's easily accessible any good AC shop should be able to do the job. If it requires disassembling the dash, you probably want to go to Autowave or Cerritos.

 

[D'Ecosse]

I guess my 134a is low/gone, which means I probably have a leak somewhere, since it was just charged 24 months ago. Darn, I was kinda hoping it was just the CCU since that's an easy drop in fix. Locating and fixing the leak is beyond my current abilities!

Now I must either try to find a good A/C place nearby (west-LA), or maybe it's worth the extra effort to take it down to Autowave? Anyone have a reccomendation?

Since it's R134a you have the advantage that you can at least get yourself a relatively inexpensive DIY recharge system from an autoparts store - you can buy the refill cans with the fluorescent green dye already included in the mix, then it will make it easier for your to detect where it's leaking from. Then you can decide on permanent course of action once the source of leak is established. Hopefully not the evaporator core!
One place to definitely check is whether it is simply leaking from the Schraeder valves - don't attempt to remove these however without having system completely evacuated.

 

[Joshs]

I have a sniffer if you want to borrow it, though it may not make fixing it any cheaper. You could just top off to keep you cool in the near-term till you get it fixed. Trace the lines around the compressor and around the condenser as much as possible. Usually the source of the leak will be grimy/oily from dirt building up on the oil that has leaked out. Often leaks happen at the unions.
Where you get it repaired will depend on where the leak is. If it's easily accessible any good AC shop should be able to do the job. If it requires disassembling the dash, you probably want to go to Autowave or Cerritos.

Since it's R134a you have the advantage that you can at least get yourself a relatively inexpensive DIY recharge system from an autoparts store - you can buy the refill cans with the fluorescent green dye already included in the mix, then it will make it easier for your to detect where it's leaking from. Then you can decide on permanent course of action once the source of leak is established. Hopefully not the evaporator core!
One place to definitely check is whether it is simply leaking from the Schraeder valves - don't attempt to remove these however without having system completely evacuated.

These recharge kits seem cheap and easy enough, I'll pick one up and see if I can localize the leak. If it's hidden or otherwise difficult to find using the UV method then I'll likely take Daedalus' offer to try out the sniffer. Hopefully the leak is in an obvious and easy to fix place (crosses fingers).

I read on another thread that it's important to avoid the refill cans that include a sealer, is this the case? It seems like most of them include some sort of extra stuff to clean or enhance or seal..

-Josh

 

[Daedalus]

I believe the sealers are supposed to coagulate on contact with air. I wouldn't risk it, especially if you have no pressure right now. The system probably has air in it. Don't risk clogging the expansion valve--major bucks. They're also bad for the recycling machines the shops use.

 

[Joshs]

I went to Pep Boys and picked up a can of 134a+dye, a can of 134a, a can of oil, and this 'ez-chill quick charge' gun with gauge:

However the connector on hose from the 'gun' doesn't seem to attach securely to the the low-pressure port. Either I'm doing something wrong trying to attach them, or perhaps I still have the r12 style ports. Did updated valves come with the retrofit kit, part #38020-SM4-A1AH? I have that part # on my invoice, along with the installation of a new high pressure ac hose at the compressor, and a couple of related o-rings. [EDIT: They are the proper valves, the connector must be aligned correctly and the sleeve must be pushed back and forth properly.]

I also noticed that I can already see some dye in the valves, but I figure I need to clean them and see if the dye returns before I can blame them. There are no obvious leaks that I can spot from a top down UV examination.

Low-Pressure Port, under blue cap:

High-Pressure Port, under red cap:

-Josh

 

[D'Ecosse]

I can't really tell for sure from your pics Josh but that would definitely appear to be source of leak (assuming you didn't already try to fill it there from open can yet). It looks like a new style ....

The r134a fitting is intended to snap over the outside - it's a quick-disconnect style fitting - typically the conversions would have a replacement screwed into the original r12 style, but it's conceivable they have removed old ones completely & replaced with the new.

To connect, you pull back on the outside sleeve of the fitting of the hose adapter as you push it over the car's AC fitting - as you push it on then snap the outside sleeve back forward to lock it in place

Here's a video I found that shows the whole process including how the hose fitting goes on.
Here's video of your actual product, also with an brief illustration at the end of the quick disconnect.

 

[Joshs]

I can't really tell for sure from your pics Josh but that would definitely appear to be source of leak (assuming you didn't already try to fill it there from open can yet). It looks like a new style ....

The r134a fitting is intended to snap over the outside - it's a quick-disconnect style fitting - typically the conversions would have a replacement screwed into the original r12 style, but it's conceivable they have removed old ones completely & replaced with the new.

To connect, you pull back on the outside sleeve of the fitting of the hose adapter as you push it over the car's AC fitting - as you push it on then snap the outside sleeve back forward to lock it in place

Here's a video I found that shows the whole process including how the hose fitting goes on.
Here's video of your actual product, also with an brief illustration at the end of the quick disconnect.

Looking at the first video, I agree that the connector looks like the new style. When I tried to connect, I pulled back the ring and the connector slips over, but it pulls off easily and doesn't seem sealed. I didn't have the engine running at the time, perhaps that's an issue, since the instructions do say to turn it on. I'll give it another go tomorrow.

As far as the visible dye on the valves - could it be left over from the prior evacuation/recharge/retrofit? I think I could even hear some pressure escaping when I removed the dust cap on the high-pressure side, so that would certainly lean toward a leaking valve. Or the sound could have just been grime sticking or something.

Thanks again!

-Josh

 

[Daedalus]

When you push the coupler down, does the ring slide back to it's original position? If not you might need to push down on the coupler a little more to get it to lock. Having the car running won't have any effect on hooking up the hose.
The dye may have been there from when it was injected. Is there any dye on the inside of the cap? The dust caps don't hold pressure. It's more likely you heard air rushing under the cap from the sudden vacuum than from gas leaking out.

 

[Joshs]

Last night I must have either not had the connector straight, or not pushed the collar in enough. I successfully got the 'gauge gun' attached this morning, but the gauge didn't register any pressure.

I added just a little 134a with dye, and the pressure rose rapidly. I then started up the engine and turned on the a/c, and saw that the compressor was engaged. Putting the gauge back on, the pressure had dropped back down towards zero, presumably as the system equalized a bit.

With the a/c on, I slowly added the entire 12oz can, and when the can was empty the gauge registered about 35 PSI.

Cold air was coming out of the vents, and I heard no strange sounds, so it appears that the system was functioning. I shut off the car, and took another pressure reading, but now it read almost 80psi!! Thinking maybe the engine needed to be run a bit, I took it for a drive around the block, and when I got home, it still read 75psi.

This is too high, right? How long might I need to run the car?

Is it time to start looking for leaks now, or do I need to wait a bit for the dyes to collect enough to be visable?

Looking at the inside of the dust caps, I can see residual UV dye, but I don't have any dye cleaner to clean them so I can tell if fresh dye is coming out. Maybe if I put a rag or something over the valves I can check it that way?

I have a 2oz can of oil (not pictured), but I'm not sure if I need to do anything with it.

-Josh

 

[Daedalus]

I strongly advise you to get it fixed properly before running the AC. With the system at zero pressure there is no doubt it contains air (and moisture) and your drier is most likely saturated. Moisture inside the system is the worst thing next to actual debris. It can ice up and clog things, and cause long term damage including ice abrasion and lubrication break-down. The air will raise pressures and stress the system. You need to replace the drier and have the system vacuumed down properly before filling with refrigerant. And before doing that you should fix the leak. It sounds like it's a fast leak, because whatever was in there when the pressure switch first cut out is already gone.

 

[Joshs]

Ok, I guess it's time to take it in. Hopefully it's not too serious, but I have a feeling it won't be cheap Thanks for the guidance!

I just hit 150k last night, maybe she deserves a fixed a/c for the milestone..

-Josh

 

[GOTTSPD]

Let us know what happens. I think mine is low on freon as well...