[jameschong]

I need to find a more permanent solution to my AC woes.

I currently have an original R12, Seiko-Seiki system.

1. The cooling capacity reduces after every 5-6 months, and I suspect a leak somewhere.

2. Recently, it has not been effective at all in stop-start traffic, but does very well along the highways

I've had the system looked at by "professionals", but everyone of them seem to have a different opinion:

1. Replace the R12 compressor. Gets very hot when running. Seems the compressor is no longer effective. Pressure gain when idle is insufficient.

2. Replace the receiver/drier. There is no indication that it has been replaced recently.

3. Replace the whole system with an R134a one.

There are still places that do R12 repairs, so option (1) is still possible. My indie Saab workshop even has an original Seiko-Seiki for sale....

What do you think I should do?

 

[grif900]

Id stay with R12, it will get cold faster than R134a and that means a shorter "duty-cycle" to cool your interior. Replace the pump.

 

[jameschong]

I forgot to add....

I have the option of replacing the compressor with a Sanden reciprocating one or the original rotary Seiko-Seiki. The Seiko-Seiki is twice the price of the Sanden one.

If I intend to replace it, I will likely go for the cheaper option. Firstly, because it might not end my woes,and secondly, because it's not likely to be sitting on the shelves for the last 10 years. My indie Saab workshop (who has the Seiko-Seiki in stock) says the c900 was "designed for that compressor". I take that with a pinch of salt.....

However, the Sanden compressor requires a bracket fabricated for it, and replumbing to accommodate the different piping configuration. Adds time and money to the Sanden solution....

 

[grif900]

many C900s came with Sanden compressors,the bracket should not be an issue.

 

[James Bond]

I had mine upgraded to R134a by Saab - really not too bad cost wise, particularly as it should now last several years without trouble.


They changed:

• Hoses and manifold to compressor
• Charge valve
• TX valve
• Overpressure valve on compressor

They did not change the drier, although I asked them to.

It now works very well indeed, yes, even with the new gas.

 

[supremedalek]

Just to let you know, there is some work being done in replacing r134 with, I believe, a mixture based on butane or something like that because it cools much more efficiently, is safer to the environment (r134 makes even r12 look like something from a health shop), and has less fire issues than r134. I will try to find out the link later.

 

[yfs87]

id remove it...

 

[supremedalek]

IMHO, a compressor goes bad when it ingests nasty bits or its seals are not sealing anymore. You can sping the compressor by hand (if you have not run it in a while) and hear (it may require being reeeally close to it) and feel how hard it turns. If none of these are happening, I would put some leak test and hunt down where it is leaking from. It could be just a o-ring somewhere...

 

[Jim Mesthene]

You need to find someone who knows what he's doing.
The first step in diagnosing A/C problems is hooking up gauges. They will tell you if the compressor is working. If it is, you're all set. There's no "better" compressor. Except for the old York compessors found on the oldest SAABs, all the compressors have excess capacity and will work fine for R134a.
You are apparantly leaking refrigerant. You need to find the leak and fix it; that's not an issue of what refrigerant you're using.
I've converted hundreds of R12 cars. If done right, they work almost as well as R12. If done right, the R134a will outperform most R12 systems that have not been tweaked to perform at their best.

 

[SaabMon]

Id stay with R12, it will get cold faster than R134a and that means a shorter "duty-cycle" to cool your interior. Replace the pump.

I had mine charged with freeze 12.No conversion necessary.It is cold!Supposedly more environmentally friendly than R134.

 

[dasander]

My 87 turbo broke a rubber hose, no more r 12. I drained the oil from the compresser and replaced it with oil compatable with r134a. Condensor was all beaten up, replaced that too. Also replaced all the hoses and the receiver/dryer. New hoses already had 134a fittings. I evacuated it with a vaccume pump, it held vaccume. I then added the 134a, and it has worked very well for the last 4 years. 134a is cheap, like five bucks a can at discount auto stores. the 134a is supposed to be 40% less efficient, so in theory my ac should only be working at 60% of what it would on R12. I've gotta tell you that it is plenty cold for me! I would not want it any colder. This fall the a/c clutch started slipping. There is no resistance in the compressor, the clutch simply does not lock up. I have not looked at it, I will before spring.

The system works so well that I turn the seat heaters on in the middle of July

 

[cdaly]

AC clutch is a magnetic one. If it is slipping, either the compressor is seized (the front plate won't turn) or the clutch coil is burned out (the front plate won't make contact). To test the coil, disconnect the wiring to the compressor (one or two wires) and connect 12V to the positive side and ground the negative (if there's two wires, one wire will be grounded through the block). The front place should hit the pulley with a sharp click and should be impossible to turn (engine off). If it doesn't click or, if it clicks and the front place can still turn, the clutch coil is bad. If the front plate won't turn with the voltage off, the compressor is seized.

 

[Jim Mesthene]

I had mine charged with freeze 12.No conversion necessary.It is cold!Supposedly more environmentally friendly than R134.

Freeze-12 is R134a with a little butane to make the existing oil compatible. It's a good product, but way too expensive for what it is. I'd just use R134a with the oil additive sold with the retro-fit kit.

 

[Matthew]

There's no "better" compressor. Except for the old York compessors found on the oldest SAABs, all the compressors have excess capacity and will work fine for R134a.

What regulates pressure in the air con system? The expansion valve?

Factory R-134a systems operate at a higher pressure, right? Are the compressors more powerful somehow?

A friend has suggested that a factory R-12 AC system on a 900 will run at factory R-134a pressures with no modifications. Is that true?

If done right, they work almost as well as R12. If done right, the R134a will outperform most R12 systems that have not been tweaked to perform at their best.

This is becoming more relevant as I think more about fitting AC onto my 900.

What are the key factors involved in doing the job right?

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[Jim Mesthene]

What regulates pressure in the air con system? The expansion valve?

The Expansion Valve meters liquid refrigerant into the Evaporator to keep it cold.
The Anti-Frost Switch shuts the compressor off if the Evaporator gets too cold, to prevent freezing.

Factory R-134a systems operate at a higher pressure, right? Are the compressors more powerful somehow?

The pressures are not much different. The pressure/temperature relationship is different. The Compressors are the same.

A friend has suggested that a factory R-12 AC system on a 900 will run at factory R-134a pressures with no modifications. Is that true?

Yes.

What are the key factors involved in doing the job right?

If you adjust the Anti-Frost Switch, using its capillary tube in the Evaporator, you can get optimum performance from the system.
If you convert to R134a and adjust it properly, you'll get the same cooling capacity as an R12 system in most cases.
At idle, in 100f heat, you'll notice decreased performance. You'd have to cool the Condenser to compensate (I've speculated about using water).

I hate to say this to a Super Moderator, but if you search, you'll find I've described the process before.
I strongly suggest you just go with a R134a system. My nephew just moved to London. If necessary, I'll visit him and come tweak it myself while I'm there.

 

[Matthew]

Say what you like to a Super Mod

I'd read about capiliary tube adjustment before but I wondered if there were any tips. I'll have a further look back through the archives.

Interesting there'd be no improvement in AC system effectiveness with a modern compressor (such as that from a 9-5).

I'm looking forward to retrofitting AC. It'll be an interesting project.

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[Jim Mesthene]

Interesting there'd be no improvement AC system effectiveness with a modern compressor (such as that from a 9-5).

Why?
The limits in car A/C systems are the amount of energy stored in the Refrigerant (Latent Heat of Evaporation), and the Heat Exchangers. Horsepower has never been a problem.
Increasing the Compressor's power won't do any more good than increasing System Voltage to 15v.