83 240D AC - PeachParts Mercedes-Benz Forum

Guest987 · #1 09-10-2014, 08:26 PM

What is the way to manually start the a/c compressor clutch on the car to add freon when it won't start by turning on by the switch in the car?

PackerEdgerton · #2 09-10-2014, 08:44 PM

There is a plug that goes to the clutch. The clutch requires 12V to that plug to force the compressor to run. You will need to supply 12V to that plug manually in order to force it to cycle. I suggest running a fused line off the battery in order to do it.

Good luck,

Packman

leathermang · #3 09-10-2014, 09:00 PM

If you have the R4 compressor... the super hockey puck...
then keep in mind that it does not have an oil reservoir like the sandens or Yorks...
so ALL your lubrication is by the oil which is mixed into and carried around the system by the Refrigerant...
If your system is low or out of refrigerant you should really really limit its running in that state...
Your safer bet is to add your refrigerant until it will turn on by the switch... by having the can in warm water... and since you have vacuumed your system it should fill nicely...
You have not said if you flushed your system...
or why you are needing to put refrigerant into it....
thus we or you.... may not know how much oil is in the loop....
very important thing to know..
you might share info with us as to the situation..... we might save you a lot of trouble and money.....

sleepstar · #4 09-10-2014, 09:34 PM

as mentioned if its in vacuum then you should be able to add enough to pressurize the system past the point that it will cycle on. you can also jumper the leads to the pressure switch at the drier

ah-kay · #5 09-10-2014, 10:03 PM

'switch in the car' - I presume you meant the ACC switch control unit. I would resolve why it won't turn on by the switch FIRST before adding refrigerant. You can always jump the low pressure switch to simulate refrigerant level.

leathermang · #6 09-10-2014, 10:34 PM

The low pressure switch trumps the other switches.....
so until refrigerant is in the system the others will not work.

Guest987 · #7 09-10-2014, 10:55 PM

So, what is the best way to check this out. It was supposed to have been repaired by a shop before I did a purchase. This was approximately a year ago. I just tried it the other night, and it would not cool. I noticed that the clutch will not engage. It has stickers on the fan shroud, that say it has a certain dye in the system for leak detection. It has the R-4 compressor. I know where the high pressure switch is by the dryer, but I don't know where the low pressure switch is located. What is the best procedure for me to follow to try to bring back up the a/c? At this point I have not done anything with it.

leathermang · #8 09-10-2014, 11:35 PM

You can figure it had a problem since it has had dye put into it..
that is not good...as it can sometimes clog up important stuff...like your Txvalve..

and it looks like whatever the dye was put in to find... did not find all the problems...
dye is not a good way to find anything... first because it will not check the evaporator AT ALL....
A pressurized dry gas.. usually nitrogen... mixed with 4 oz of R22 can be used with a sniffer to check the system for leaks.. including the evaporator by putting it into the center vent....
You can start with reading the last reference in my signature... the AC thread...

AC work is a pain.
there are rules you need to follow to keep from making things worse...
so take your time and read lots first..

If you are going to do this yourself you need a set of gauges...

The system has safety switches built in... so if the refrigerant is low... it will not turn on so as to protect the Compressor... so put gauges on high and low side and see if you have any pressure in there..... then report what you find...

ah-kay · #9 09-11-2014, 12:50 AM

The high pressure AND the low pressure switches are all in same place, where the receiver drier is. The function of the high pressure switch is to switch on the aux fan to cool the condenser. The low pressure switch is to assert there is enough R12 in the system. The low presssure switch overrides all the control. This is what I would do. The dye is in there so I would leave it the way it is. You can check whether the compressor would run by jumping the switches. Remove the wire harness on the r/d and short the harness with a piece of copper wire. If you do not know which one is high or low just jump both. Start the car and push the button for A/C. If everything within the ACC works then the compressor should engage. Make sure you only runs it for a short while, less then 30 sec to do a visual.

Has the system been vacuumed down? If it has and the compressor runs then you can remove the jump wires and charge from the lower pressure port. It is possible that the R12 pressure from the can would activate the low pressure switch and starts the compressor. If not then you may have to leave the jumper wires in place until enough R12 is sucked in to activate the switch.

A/C is not as complicated as it made out to be. Make sure you wear safety goggles and protective clothing. I have done a lot of R12->R134 conversion and A/C repairs and my average DIY skill never fails me. Good luck.

leathermang · #10 09-11-2014, 07:42 AM

AC is not complicated in one sense..
but one must follow some very specific rules if you want to fix it so it will last many years.... and not ruin anything in the learning process...

Goggles an absolute must for safety..... don't break that rule....
and I do not mean safety glasses.... a combination of goggles over the eyes....and a full face shield.... as one might be outfitted when doing wood turning ......would not be overkill....

Guest987 · #11 09-11-2014, 02:39 PM

Getting back with info after setting up the gauges on the car. With the couplers open LS & HS and the manifold valves closed I have no pressure at all showing on the gauges!

leathermang · #12 09-11-2014, 04:32 PM

Not surprising given what else you said...
so, no chance of the garage that was supposed to have fixed it doing it right ?

If not..
you need to figure out where your leak/s are..

and only pressurizing it with something a sniffer can smell is really effective..

You don't know any shops you can trust to do this stuff ?

Guest987 · #13 09-11-2014, 05:06 PM

Is pressurizing it like your saying hard to do? The sniffer you refer to that is probably an expensive device, as well, I suppose. If it had the dye in it like the shop mentioned could it be scanned with an infared light to maybe tell where it dumped all the freon out? A total loss kind of points me in the direction of the A/C compressor, but it is a guess. I tried to go back to the p.o. on the issue before I posted on the issue initially, because on the bill it showed 12mo.'s or 12,000 mile warranty. The p.o. wouldn't concur on doing that at all. All I got was you need to find the problem with it. The reason I mentioned the compressor was on the 1st. time the shop repaired the A/C on the car the bill was 1200 or more, and it showed they replaced the seals in the compressor. The last time was just before I bought the car. The success of a shop doing well on that is very, very slim from my experiences in the past. I wouldn't have accepted that, if it would have been mine.

Guest987 · #14 09-12-2014, 10:49 AM

I was wanting to check if anyone knew of a DIY procedure on troubleshooting the A/C systems that pertain to the 240D? I looked in my old Haynes book and they don't cover anything...just take to like a dealer or M-B shop. I am interested in leak detection procedures, as well as, recharging. Procedure to possibly regress back to the old R-12 system. The do's and don't's so to speak. I didn't find anything under Pelican on it. Any response or help would be appreciated. TIA!

vstech · #15 09-12-2014, 01:15 PM

you could always read the thread on my signature... or leathermang's same thread.
it's got a LOT of AC info...