With record breaking temps up here in Montana, its about time to get the A/C on my 85 300sd working. I had the compressor replaced during the winter and the MB shop told me that they couldn't put in 134a because they didn't know if it was compatible with the Freeze 12 that was in the system.

They did drain it, but now I need to know two things- can I put 134a on top of freeze 12? And how the heck do I get the right fiting so that the cans of 134a will fit on the correct nozzle?

-Travis

"Freeze 12" is 80% R134a and 20% R142 anyway. You can buy conversion fittings at most auto part stores.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I bought one of those conversion fitting systems but it still wouldn't work out, even though it said it works with "all cars". Perhaps I am trying to add the refridgerant to the wrong valve....

When recharging you add the 134a with the car running and A/C on correct? And you add it to the "low side" which should be a valve in between the compressor and the evaporator, correct?

Correct on both counts. Note also that the low-side line is much larger than the high-side line.

And you often need to bring the engine to a fast idle, say>1500rpm.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

OK so fast idle the engine with max AC on while doing all this. But I still have the valve wont fit problem.

All I do is unscrew that little cap with my hand and attach the hose correct? Or do I have to unscrew the cap and then use a wrench to remove the fitting so that I can get the recharger hose closer to the actual valve? (the problem is the little nipple on the recharge can doesn't reach far enough into the fitting in order to depress the valve and get it pressurized)

Thanks for the help with these relatively simple questions....

there is a collar that lifts to push the hose in just like an air compressor fitting.

There is a collar on the hose going to the refill can. Even with it fully lifted back, there is no contact between the valve on the car's hose and the nipple coming out of the refill hose nozzle.

also, if you are not putting the entire can of 134a in, always charge with the can upside down. this freon is a mixture of several chemicals, and it will seperate at differant pressures. so you need to put in the liquid, VERY SLOWLY if the system is running.
it is best to weigh the correct charge and put it in on the liquid side *(small line high pressure fitting) after evacuating the system and with the system NOT running.
but minor charging can be done on the low side, just use liquid with the can upside down.
John

Now I'm confused. I thought everything I've read says that on the low side, with R134A, NOT to turn the can upside down......

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

does your low side hose fitting have treads? if so it is the oe R12 fitting. If not the 134a fitting has been screwed onto it, as stated it looks like an air compresor tool fitting (no threads, push on and lock)

be cafefull charging a liquid into the high side. i would rather charge a gas into the low side (can upright). if problem, you can put the can upright in a can of warm water to help get it out, depends on your ambient temps. charging liquid into the low side (can upside down) goes straight to the compresor which could break the vanes. under operation, the compressor recieves gas from the evaporator, it does not turn to liguid until after the condenser, which is high side with lots of pressure.

as for freeze 12, do a search and brace yourself for the lengthy readings and opinions.

if compressor was replaced during the winter, why was it not charged then or did it leak out?

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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification

It wasn't charged because the shop claimed that they didn't know if they could convert freeze 12 over to 134a and since they didn't have freeze 12 that I needed to go somewhere else.

The low side hose fitting has a screw-off cap and then there are threads. Its probably the R12 fitting... but I think I might need to remove the cap and then wrench off the fitting to get to the actual valve. I'll post some pictures if I still haven't figured it out.

Thanks for the upright/upside down comment, I will have to look more into that.

You're not confused. The can should never be inverted if you're charging with a running compressor.

The best thing is to charge with pure HFC134a. Don't get the stuff with oil or o-ring conditioner in it. If you need either of those, add them separately, before adding the refridgerant. And note that freon is CFC12, not HFC134a.

This is correct. It should be noted that you should absolutely never connect a container of refriderant to the high-side port with the compressor running. You could hurt yourself.

If it's the R12 fitting, and it sounds like it is, you do not want to remove the core. It will vent the refridgerant. The 134a retrofit adaptor will screw right over the R12 fitting with no changes to either.

But you may have to post pictures. You could have a Freeze-12 fitting over the R12 fitting. All refriderants have distinct fittings to prevent accidental introduction of the wrong type. It's not legal to mix them...