A/C failing
 

We've had a string of 90 degree days so I'm starting to use A/C for the first time since September.

The cold air comes out very sporatically. It will never immediately blow cold air, although the fans will come on at full speed right away if A/C is needed (climate control set to 65 while interior of the car is 100+). After several minutes of driving, it will eventually come on, no set time or engine temp though, very random.

After a while, it will just stop blowing cold air again and be blowing warm air. Then come back after a while, etc, etc.

When it does blow cold air, it feels about right, although I wouldn't call it "ice cold" as I've felt in other cars.

It's been this way for years, but I figured it just needed a recharge maybe. In November YT converted it and recharged it. It was November so we couldn't really test if that changed anything. Now that we have hot days, it looks like that didn't solve the problem. Suggestions?

Re: A/C failing
 

A good place to start would be the self diagnosis function of the climate control system.

Re: A/C failing
 

Have you checked the HVAC system codes? We had the same exact problem on our Trailblazer and it turned out to be a pressure switch on one of the coolant lines. Find the two-wire switch on the line I think and tap it after the problem arises.... I checked the SVX manual but couldnt find the location of the switch.... but it should be up top.

Re: A/C failing
 

My guess would be that the system is undercharged, but since it has been retro-hacked there is no way of ever getting the refrigerant charge right. There is some sort of formula that converts R-12 capacities into a reccomended 134a charge amount, which will get the pressures in the system kinda-sorta in the neighborhood of where they should be. If the charge is approximatly correct, then you probably have a problem with one of the sensors in the climate control system, the favorites to fail on these seem to be the evaporator and refrigerant temperature sensors.

Hold the OFF and AUTO buttons and turn the key on, then post the results. Anything other than a display of '00' is abnormal once the test completes if you do it outside in the sun.

Re: A/C failing
 

Thanks guys, I had forgotten about the climate control self-diagnosis.

I got a code 14 "Evaporator sensor open".

Re: A/C failing
 

WOW! oh i mean WOW! a climate control self diag, is this common in cars coool! I'm a little behind in the newer car biz..............G

Re: A/C failing
 

Haha, it was actually pretty advanced at the time.


The evaporator temp sensor is quite a pain to replace, you have to remove the box which contains the evaporator and then open it up. On some of the cars it the sensor is actually stuffed into the evaporator fins and on others it is suspended right in front of it. My 92 was one way and the 94 was the other way but I can't remember which was which. Unfortunately this isn't a job for the do it yourselfer. I would take it to a reputable shop, and take this opportunity to fix it correctly and remove the retrofit connectors, and charge it back with r-12. Also, don't forget to have the receiver dryer replaced.

Re: A/C failing
 

:( Wow, that doesn't sound cheap. :(

Pain to replace usually = $$$$$

Charge back with r-12? Didn't know they still did that, thought it was just totally not produced any more (I just assumed). So what if down the line I need a new compressor? Is that still r-12 or is that when people convert? Sorry, I know nothing about this stuff, just that a lot of people I know have done the simple wal mart conversion kit, and also that the compressors give out eventually and need replacing, to the point it's one of the few oem parts Motorsport Warehouse even sells.

Funny thing is, once I ran the diagnostics, when I started the car the A/C came on right away. And for the last 2 days it has worked flawlessly, almost like the test somehow reset and corrected the system. I doubt it though. At the same time, I don't think intermitent A/C is enough to warrant what sounds like several hundred dollars of repair.

Re: A/C failing
 

The compressors die after retrofitting because they are not designed to work with 134a which uses higher pressures and carries a different oil. The oil used in 12 will literally react chemically with the oil used in 134a and cause corrosion in the system. The o-rings, hoses, and the desiccant, which is similar to the stuff that comes in pill bottles that says "do not eat" is not interchangeable between the two gases. The o-rings and hoses are also not compatible with the oil in 134a. Usually, it is on an older vehicle which is probably not going to last the time it will take to damage the system. Aside from those parts, the compressor and expansion valve, as well as the evaporator and the condenser are different between the two because r134a runs at higher pressure than does r12 (i.e it is less efficient). So, usually every part is different in the system.

Because of the different pressures and properties of 134a, it is no longer accurate to charge it until there are no more bubbles in the system as seen through the sight glass. This is further complicated by the variable displacement compressor used in the SVX, which already renders the sight glass useless. (even with r-12)

Handling R-12 requires a course be taken, along with a certification test, both of which I have earned. This course costs money, and so most shops simply carry 134a and sell the retrofit service to avoid it.

A final thought on the matter and perhaps the most interesting is one of economics. 134a at the dealership I work at is priced at 12.95/lb while r-12 is 28.95. The SVX holds about 2 lbs, so that's a difference of $32. Most retrofit kits are about $30-50, and most shops charge you an extra $50 for that service. SO, you have destroyed your a/c system AND you paid extra for it.

Re: A/C failing
 

So from your experienced point of view, sounds like the retrofit is a bad idea. Like I said, I've known lots of SVX owners that have done it around here, and YT himself did the retrofit on my car.

So is there a "right way" to convert a 92 SVX to 134a, such as using all A/C system parts from a 94+ model? Or would there be so much work involved that it would cost much more than just keeping the R12 system limping along?

Re: A/C failing
 

Excellent info, good to hear this type of stuff from someone in the know.

I hope I'm not hijacking this thread as my info may help others!

I've converted my system over to r134a by replacing all components (comp, cond, evap, etc) and O rings.

Using a Robinair vac pump, system was evacuated and held vacuum for > 1 hour.

Since the sight glass inspection is not valid, I'd like to know what pressure should I be seeing in the manifold gauge set (high and low). So far, only one 12oz can has been emptied into the system. I'm assuming at least one more can is needed but I won't proceed until I know some more info.

Currently, my low side is at 28 psi and high side is at 210 psi, at engine idle. Vent temp is at 48 deg F (fan on Max, temp set at 65*) and the ambient temp is around 85 deg F approx.

According to the How To Locker, I see that we need 22 oz of R134a, with a pressure gauge reading of: 28 psi low, 185-213 psi High.

So, do I dump in two cans of R134a or do I pay attention to the gauge set during recharging?

Thanks for any insight.

Cheers.

Re: A/C failing
 

I have no idea why people are still even using 134a :confused:

Does everyone on this form not know that a direct replacement for 12 is available that requires no oil change??

Strange...

Keith:cool:

Re: A/C failing
 

The remanufactured compressor in my silver SVX was labeled for 134a.

dcb

Re: A/C failing
 

Do tell....

Re: A/C failing
 

I just did a check on my '92 Claret, and got a climate code 15:

15/25 .......... Open/Short In Refrigerant Temp. Sensor Circuit

This fits with my symptoms. The a/c comes on slowly and is cold, but shuts-off in a minute for no reason. If I shut off the engine & restart, it comes on cold again. If I do this a couple of times it will stay on cold. I was thinking it was some kind of sensor problem, because it seems to stay on if the rpms are up over 2000 on the highway.

Anyway, the troubleshooting "how to" document says to pull the glove box and check the resistance on the harness and or replace the sensor. I'm thinking with my symptoms I should just replace the sensor (anybody got the part # handy?). Is the glove box hard to pull? Anybody got a link to some instructions?