Aircon query

Simon · 05-19-04, 03:40 AM

The aircon on my GTD needs filling. It was built in 1990 and hasn't been used since 1995. Is there an issue with the gas used? is there a "new" and "old" type of gas here in the UK? if it's the "old" is my system compatible?
Thanks
Simon

Bill Bayard · 05-19-04, 04:38 AM

Local regs vary, but R-12(in your A/C) is being phased out
in the States, being replaced by R-134(eco-friendly).
Try contacting a shop that does automotive A/C work. They should be able to help you out. R-134 is much cheaper than R-12, and it cools as well as R-12. Changing from R-12 to R-134 shouldn't be a big deal.

Bill

Tony Hunt · 05-19-04, 04:47 AM

Simon,
My aircon was in exactly the same condition as yours - car built in 1996 and the previous owner had accepted that it didn't work and that was that.
It transpired that the main fuse had blown, so there were no blowers either! But he only did 250 miles in 18 months so probably didn't notice it.
When we came to degass the system - it was empty. This is quite common as the seals leak if the system isn't used. I had to move the blower box and re make all the hose connections, so put fused relays into the 3 blower and mag clutch/condenser fan lines at the same time. The switches may burn out otherwise. I have a good source of very neat fused relays which slot together into a bank, if you would like to PM me.
Also expect that valves and switches in the system may be sticking or have to be replaced.
The best way to tackle this and the refilling problem is to find a good local aircon man and cultivate him! The GTD system is pretty conventional, I'm told, so a good technician shouldn't have any problems.

Jools · 05-19-04, 09:16 PM

I belive Dave at Borden Tyre & Exhaust has just installed a fancy new air-con refilling/testing machine. Could be just what you need. 01420 477655 or you can PM him from the Forum.

Howard Jones · 05-21-04, 01:22 PM

Simon, I'm sorry to tell you that there are a LOT of differences between 134a and R12 systems. Starting with the compressor oil and ending with the fittings on the end of the hoses. 134a systems use o-rings because the R12 flare fittings will not hold 134a gas. The expansion valves are different, along with the charging ports. The R12 charging ports will not except a hose fitting comming from a 134a tank.

Don't pannic. Check out www.vintageair.com
These guys have a lot of information on their website along with complete build your own system information in their catalog. The catalog also goes into the difference between 134a and R12 systems.

Tony Hunt · 05-21-04, 01:35 PM

Howard, does that mean you can't put R134a into an R12 system?
From what you say about the compressor oil, this could be the case. The different filler fittings are obviously designed to ensure one type is not put into the other, though replacement of a single hose could get round that. . . .
One question which you might be able to answer, Howard - does the compressor compress gas or pump liquid refrigerant?

Tony Hunt · 05-21-04, 01:46 PM

[ QUOTE ]
Don't pannic. Check out www.vintageair.com

[/ QUOTE ]
Cool wiring downloads at http://www.vintageair.com/downloads.asp!! [img]/ubbthreads/images/graemlins/cool.gif[/img]

Howard Jones · 05-21-04, 04:48 PM

Several people have have told me if you mix them it will turn into some awful crap and cause you to take it all apart and clean it out. Compressor, lines, evap, condensor, etc. So I would not mix them... ever. Now can you completely drain your compressor and evacuate your system of the old refrig. refill and get away with it? I believe you can, but 134a usually leaks by the flare fitting found on r12 systems and will require you to recharge the system from time to time.

Depending on where you are in the system, while it is running, you have both gas and liquid at different pressures and temps. Time to visit the library and read up on air con theory.

Again I'm just trying to save you a problem you can avoid by going and mixing refrigerents before you find out all the facts.

Any air con types out there?

Eric · 05-21-04, 11:53 PM

We have been doing retrofits from r12 to r134a for years now. It consists of, drain the r12, drain as much oil as possible, measure it, put in the equivelant amount of new oil, red loctite on fitting adapters and fill. Never had any problems, the odd expansion valve freezing, thats it, and still very rare. There is 2 types of oil, ester and pag, i think, i beleive in a brand new system, pag is better, but in a retrofit the ester mixes better. I don know some Ford and GM cars have the odd issue but for the most part, converting is fine

Tony Hunt · 05-22-04, 06:16 AM

It's not my intention to hijack this thread, but Howard and Eric seem to be well into aircon and might be able to answer my query.
When my system was recommissioned, the aircon man said that the thermostatic expansion valve (TXV) is partially restricted and was not regulating refrigerant flow. He also said that the system would work but should not be used until the valve has been changed, but didn't say why.
The system does produce cold air, but after about 45 minutes its effectiveness seems to diminish. I have never driven an aircon car before and had not been able to drive this system with a serviceable TXV, so have nothing to compare it with.
Is it harmful to operate the system in the hope of freeing up the valve? I'd rather try this as it sits on the end of the evaporator/blower box in the GTD and is a bind to get at in addition to requiring another degas/regas.
Any ideas please? [img]/ubbthreads/images/graemlins/confused.gif[/img]

Eric · 05-22-04, 10:28 AM

Tony, I dont see any reason that the sytsem will get damaged, but i also dont see it freeing up either. I have taken them apart and tried to free them up, never beeen successful.
Usually something gets stuck in it, like the desicant from the reciever dryer assy. Generally, when one goes, replace the other. If it works, use it. IF it isnt good enough, your going to have to replace it.

Tony Hunt · 05-22-04, 03:09 PM

Many thanks, Eric. Sounds as if I'm not doing any harm, so I shall run it some more until I have the time to take everything down and replace the TXV and the silica gel dryer pot.
What exactly does the TXV do, anyway? [img]/ubbthreads/images/graemlins/tongue.gif[/img]

Howard Jones · 05-23-04, 01:47 AM

Since I have a GTD also I am aware of the process of changing the expansion valve. I would do as you have sugested and leave it until you rework your system.

The expansion valve regulates the flow of gas from the high pressure side of the system into the low pressure internal area of the evaporator where the gas now cooled, by the voodoo of expanding gasses cooling as they loose pressure, fills the evaporator and as the fans blow air over the coils cools the cars interior.

Your slow reducton in performance can be caused by both the condensors small size, the radiator looking thing back in the engine bay,and it retaining too much heat over time as the engine bay heats up. I replaced mine with a much larger unit and mounted it in front of the water radiator for just this reason.

The "jet" in the expansion valve is very small, much smaller than a holly main jet and if blocked or of the wrong size will also reduce the overall performance of the system. This is why the two types of refrigants have different calibrations for the expansion valve "jet" size
and why 134a requires a different expansion vave than r12. When you redo your system, if you change gas type then I would recommend that you change both the drier and the expansion valve, drain the compressor of oil, and evacuate the system before you refill the compressor with the correct oil and recharge with the new gas. I have been asking about the fitting issue and if you can get it, the R12 system, charged with 134a and the charge holds up for the summer then go ahead and leave the flare fittings. 134a isn't all that expensive to recharge each spring.

Good luck

Rick Muck- Mark IV · 06-04-04, 06:32 AM

A compressor pumps the refrig in a gas state, if it tries to pump liquid it does a nasty hydrolock thing! When R12 to R134 changeovers were first done there was concern that the 134 would "wick" out of the hioses as the molecules are smaller. In fact most systems did not leak as the hose walls had been coated with the ester oil and this acted liked a barrier. 134 is somewhat less efficent then R12 so a change over system will cool about 80 percent as compared to R12.

Rick