Fixed AC - PeachParts Mercedes-Benz Forum

sailor15015 · #1 01-12-2006, 04:51 PM

Well the unseasonably warm winter finally forced me to start fixing the ac on the '84. It worked when my brother owned it but quit a few weeks before he sold it to me. I was resigned to putting oil and a charge in there and trying to find the leak. For the life of me I couldn't get the compressor to turn over. I tried jumping the drier pressure switch and that wouldnt work. Then I thought I was really screwed. Before I got really down I looked under the car and one of the electrical connections to the compressor had worked loose! Bingo! It works like a charm. I added a little refrigerant and oil because it was a bit low and it froze me out! The aux fan even works like its supposed to. I think the excessive shaking from my worn out rack dampener bolt helped to shake it loose. That's the next thing on my list. Glad the ac turned out to be so easy. Now I can face the 70 degree temps in January without fear.

TheDon · #2 01-12-2006, 04:53 PM

ive got two lil electrical plugs that come off the dryer that arent plugged into anything.. ill take pics later .. but what refrigerant is supposed to go into these systems.. it says r-12 but i thought that stuff is now banned.. i have a neighbor that is an HVAC tech maybe he can hook me up

didget69 · #3 01-12-2006, 05:34 PM

R12 production is banned; there is still a good bit of R12 refrigerant on the open market, but it's up there in price - hmmm, but then again, R134a has been going up as well pricewise...

#4 01-12-2006, 05:41 PM

R12 is still available for those with a 609 license. For $15 and an hour or two of work you can get the 609 license with an open book test at www.imaca.org.

R12 is coming down in price while 134 is going up in price. I bought it last year for less than $15 per pound while 134a was pushing $10 per pound. It could very well be that this year the prices will equalize. It now is just not worth converting an R12 system to anything besides R12.

Good luck,

sailor15015 · #5 01-12-2006, 05:57 PM

If mine already hadn't been converted with a new compressor and a parallel flow condensor I wouldn't use r134a either. I like to stick with the original stuff but so far r134 is good. Its just more convenient because you can walk into almost any auto parts store and buy it off the shelf, no license required. I would, however, take the time to take the test if a p/o hadn't already converted it. I think the two connectors that face up are for the pressure switch and the two that face towards the driver's side are for the temp switch for the aux fan.

Oilbrnr · #6 01-12-2006, 06:42 PM

I'm kinda in the same boat, the compressor is not coming on. PO (BraveRichard) said that it is full of R12, but the Hi/Low switch might be intermittent. I have not yet started to diagnose the problem, but I will look into it this weekend.

Should the switch turn out to be bad, I can have someone salvage my R12 and put it back in correct? Also, the switch right on the drier is for the aux fan?

#7 01-13-2006, 09:09 AM

Yes, most shops have a recycling machine that will recover the R12, clean and dry it and then you can put it back in.

Depending on which switch is bad, however, it may not require emptying the system. One of the switches is thermal and simply threads into a closed hole in the r/d. The other is indeed a pressure switch and requires emptying the system, evacuation and recharge.

Don't jump the gun and assume that a switch is bad. It is quite common for there to be wiring problems, a bad relay or any number of things. Measure twice, cut once.

Good luck,

Diesel Giant · #8 01-13-2006, 10:22 AM

If you have r-12 then use it. I like to use Freeze 12. Get colder than r-12 and works great.

http://dieselgiant.com/repairyourac.htm

Oilbrnr · #9 01-13-2006, 11:32 AM

Quote:

Originally Posted by LarryBible

Yes, most shops have a recycling machine that will recover the R12, clean and dry it and then you can put it back in.

Depending on which switch is bad, however, it may not require emptying the system. One of the switches is thermal and simply threads into a closed hole in the r/d. The other is indeed a pressure switch and requires emptying the system, evacuation and recharge.

Don't jump the gun and assume that a switch is bad. It is quite common for there to be wiring problems, a bad relay or any number of things. Measure twice, cut once.

Good luck,

True! I'll do a full diagnosis tomorrow to determine what is getting juice and what isn't.

However, isn't the switch that is directly attached to the drier a temp sensing switch to activate the aux fan (and could be removed without losing refrigerant)? The other is in fact a high/low, not allowing the compressor to run if the freon level is too low, or pressure to high?

braverichard · #10 01-14-2006, 11:12 AM

Yes you are correct on those switches.

Matt L · #11 01-14-2006, 11:33 AM

Quote:

Originally Posted by Oilbrnr

However, isn't the switch that is directly attached to the drier a temp sensing switch to activate the aux fan (and could be removed without losing refrigerant)? The other is in fact a high/low, not allowing the compressor to run if the freon level is too low, or pressure to high?

Almost correct. The pressure switch was low-pressure only for the CFC-12 system. If you get a replacement switch, it will also have a high-pressure cutout, which is required for HFC-134a, but won't harm a CFC-12 system.

boneheaddoctor · #12 01-14-2006, 11:37 AM

I just got my 609 and I plan to use R-12.....the real stuff not the other stuff.

braverichard · #13 01-14-2006, 11:39 AM

One of the biggest mistakes I ever made was retroffiting my 300SD to use R134a. However, I did that back when I didn't know anything about these A/C systems and how easy it is to get the 609 Certification. I have since received that certification and purchased several pounds of R12, some of which I used to recharge the car that now belongs to Oilbrnr.

stephenson · #14 01-14-2006, 01:57 PM

Larry,

Price at $15 a pounds sounds great! I hadn't checked prices in awhile ... I did the certification gig as R-12 was getting close to restriction ... piece of cake ... took about 30 minutes, tops. Was all paper at the time. Like carrying a concealed weapon permit - I walked into an autoparts store, asked about R-12, got a scared look from the manager, flashed the certification card (like Belushi in Blues Brothers), was escorted into the manager's office where he had the R-12 hidden under a counter ... cool!

Bought 20 cans - that I now cherish and use only when I have to ...

Another short story ... prior to that had bought the last cans in Montgomery, AL around 1988 for $0.67 per 12 oz can ...

boneheaddoctor · #15 01-14-2006, 02:01 PM

Trying to find a big enough supply at the right price for my own needs right now...

nobody try to outbid me . OK.