Routine maintanence A/C system - PeachParts Mercedes-Benz Forum

vtmbz · #1 06-07-2018, 12:45 PM

My 1985 190d has a working a/c system, at least in my cool northern climate.
But there is always a drip or two of oil around the compressor, and I know it isnt from the engine, which is nice and dry.

So I was wondering what sort of preventative maint might be practical in such a unit. Its oem Im sure, and as noted, puts out cold air when asked to. It hasnt had a touch up recharge in four years. I hate to say it out loud, but the last time I did it, I used one can of freeze-12 and no oil.

Simpler=Better · #2 06-07-2018, 12:59 PM

If it works, don't touch it. Put your budget money into a jar for a r134 sanden conversion down the road.

Diseasel300 · #3 06-07-2018, 01:04 PM

A 190D should already have a Denso compressor, so no Sanden conversion needed.

If it's cooling adequately don't touch it. Once it starts struggling you can adjust the charge again. When it gets to be that you have to adjust the charge more than once a year, time to replace or re-seal the compressor.

vtmbz · #4 06-07-2018, 02:02 PM

What about the film of oil on the outside of the unit. Is that something that should be addressed?

Diseasel300 · #5 06-07-2018, 02:47 PM

The only way for the oil to get out of the compressor is to take refrigerant with it. Above the compressor you also have the vacuum pump, the power steering pump, secondary fuel filter, and the injection pump. Any ONE of those could have the most subtle leak and it will wind up on the compressor.

Again, if it isn't leaking refrigerant, don't touch it. Let it ride until you have to keep adding gas. The Denso system has a good 8 oz of oil in the system and unlike the earlier R4, it DOES have an oil sump. Lose no sleep...

tjts1 · #6 06-07-2018, 03:48 PM

Add oil. It's not that hard

vtmbz · #7 06-07-2018, 03:51 PM

Sleep found! Its true the PS pump might be the culprit after all. Ive read hundreds of a/c threads and seem to remember someone saying that compressors weep oil by default for some reason (maybe because theyre old?).

I get pretty good cooling on the hwy even on what we call hot days. Once got in a traffic snarl in Boston (where cows laid out the streets) and the surface temp was 41d C, which seemed pretty hot. The old girl stayed under 110d c and the a/c was able to blow tepid, which under the circumstances was reasonable. I doubt anyone in Dallas would find that acceptable however. Lucky for me, the competing Duckboats resolved their dispute over precedence, and we all got moving.

vtmbz · #8 06-07-2018, 03:52 PM

Quote:

Originally Posted by tjts1

Add oil. It's not that hard

Just saw this. How much to add and how is it done?

tjts1 · #9 06-07-2018, 03:53 PM

Quote:

Originally Posted by vtmbz

Just saw this. How much to add and how is it done?

Get a can of oil + r12 in eBay, put it all in. The amount is not that critical.

1983/300CD · #10 06-07-2018, 04:02 PM

Is the stuff from the parts store lacking oil? Will constant refilling with only freon eventually cause your compressor to run low on oil and/or fail?
Or if this is oil, where would you put it? I don't recall seeing an oil fill cap.

Diseasel300 · #11 06-07-2018, 04:29 PM

Oil goes in through the service port. Before adding oil, STOP. If the refrigerant isn't leaking out, the oil you see is from another source or is a "sweat". Don't add any.

If you're constantly adding refrigerant, quit it. Fix the leak, flush the system and add adequate oil compatible with the refrigerant you're running.

Too much or the wrong oil is far worse than being slightly low. Too much oil will impede flow of the refrigerant and can "oil-log" the evaporator. Get enough oil in there and the compressor will try to compress a slug of liquid oil and you'll be buying a new compressor.

1983/300CD · #12 06-08-2018, 09:00 AM

So this "service port", is that the same hole as where you put the freon?

Diseasel300 · #13 06-08-2018, 10:19 AM

Yes. Make sure you put in the right kind of oil for the refrigerant you're running. R134a takes PAG oil, R12 takes mineral oil. Don't mix and match. Don't add a random amount of oil either, see above. If you're leaking enough refrigerant to need oil, you need to bite the bullet and re-seal the system, blow out the lines, and add a known amount of oil.

barry12345 · #14 06-08-2018, 10:43 AM

If looking for something to do air conditioning wise. Check the condenser and clean it up if really dirty. May improve the system performance. It also may never have been cleaned.

Can also reduce the engine temperature a little if more airflow is getting through it. The same increased airflow is also going through the radiator. Besides removing anything larger. The son in law is fan of using foam to lift the accumulated dirt. And spraying it off with water.

Simpler=Better · #15 06-08-2018, 01:26 PM

Quote:

Originally Posted by Diseasel300

Oil goes in through the service port. Before adding oil, STOP. If the refrigerant isn't leaking out, the oil you see is from another source or is a "sweat". Don't add any.

If you're constantly adding refrigerant, quit it. Fix the leak, flush the system and add adequate oil compatible with the refrigerant you're running.

Too much or the wrong oil is far worse than being slightly low. Too much oil will impede flow of the refrigerant and can "oil-log" the evaporator. Get enough oil in there and the compressor will try to compress a slug of liquid oil and you'll be buying a new compressor.

Yup, can back this up from every HVAC tech I've ever tlalked too.