heater\AC\blower issues - Page 2 - PeachParts Mercedes-Benz Forum

SD Blue · #16 02-05-2007, 11:48 AM

I hope you didn't pay that shop much, if anything. Do you mean they hooked up guages to your system and using coinciding ambient air temps, did not verify that it was correct? How long did the car run, in a/c mode, before they took the readings?

Actually, your system may be overcharged, if their readings are, in fact, correct. The Haynes manual on auto-airconditiong quotes 22/low/suction and 265/high/discharge at ambient air temp of 80F. What was the ambient air temp? (measured 2 in. in front of the condensor) Even then, outside air temp would be off the scale (100F++) for that pressure reading on the low side.

How much do you trust their readings?

Actually you are local to one of the trusted sites mentioned by some of the air-conditioning veterans that frequent this forum. Try www.ackits.com they are located in Phoenix. They also have a forum strictly for automotive air conditioning.

vstech · #17 02-05-2007, 12:11 PM

I agree with SD Blue, 45 with R12is way high. you could be over charged, you could have the wrong refrigerant you could have a bad compressor... hard to believe the shop that checked your pressures did not follow up and explain the issues.
with the car running, a/c on max, behind the passanger's headlight I believe is the reciever/dryer and it has a small glass porthole on it, shine a flaslight on it and if you see bubbles in it, the charge is incorrect, or you have insufficient condenser cooling (ie fan not running/bugs in the condenser) you should have two hard lines leaving the compressor, the large one should snake it's way over to the firewall, find a place on that line that is not insulated, and feel it to see if it is cold as a can fresh from the fridge. if it is colder, you have a problem, if it is warmer, you have a problem.
good luck,
John

1981_300sd · #18 02-05-2007, 01:03 PM

Ok just checked, was not able to see anything at all in the sight glass. No bubbles, but almost looked clear. So of course could be a properly charged, not empty. But for sure did not see any bubbles. I started the car and ran the AC for about 5 minutes, the line you speak of, right after the reciever dryer with the glass on it, feels just as you said. About like a cold beer from the fridge. So would this indicate that the cooling system is working correctly, and that I need to look further into a venting issue?

So the proper lines are cold, no bubbles, 45 psi on the low side (at about 70 degrees outside or so, and no explaining - just a quick reading - didnt charge me anything) and the middle vents are working ok.

What else could it be? On my old 79 mercedes, the previous owner put a water hose on off swich, cant remember the name of them for the life of me right now, that basically cut the coolant off to the heater block in summer, and winter I would open it back up to get heat. Could that be a posibility, that the AC is working fine, but is getting heat mixed with it also creating a neutral outside ambient temperature?

Thanks so much for the assistance with this. Im in a race with the summer heat here. Yesterday, it got 78 here. So I will need that ac soon!

vstech · #19 02-05-2007, 01:17 PM

oh, to have 78degree days in February! (I'll pass on the 118F summer temps though

)
no, the line you need to feel is about 3/4 inch in diameter and it will be coming from the compressor, not the receiver. I think it usually goes across the front of the valve cover, but it may not on your car. if the line leaving the receiver is cold, you have a plugged line, and probably an overcharged system to compensate.
at 70F ambient, the low pressure would be around 22psi... and you might even get some frost on the large line...

SD Blue · #20 02-05-2007, 04:38 PM

An overcharged system, especially by that much, will be a detriment to a/c cooling as much as too little charge. Overcharging reduces the efficiency of the condensor, the component that gives off heat to the outside air.

1981_300sd · #21 02-05-2007, 09:15 PM

Bad news, I think

Ok so I found the hose your speaking about. Is it the larger sized one with a area for the high pressure attachment? If so, ya it was not hot, but it was not cold either. Had the ac turned on the entire way home from work - about 15 miles. Checked right when I got home. The other tube, I would say 1/4 inch or so, that goes from the drier (with the sight glass) was very cold. In case I got the wrong hose, I felt most of them down in that area, and the only cold one was the small hose from the drier.

I would assume that I have a bad compressor? Or as stated above a blockage in the line? If it is blockage, can it be flushed or do components need to be replaced?

Thanks again everyone.

1981_300sd · #22 02-07-2007, 02:06 PM

Anyone have any suggestions?

vstech · #23 02-07-2007, 02:41 PM

Sorry, been too busy to get back here.
if you are getting cold on the small line, you need to have all the refrigerant removed, then open the system and find the blockage and remove it. if it is cold right as it comes out of the receiver, you will most likely have to remove the receiver.
it sounds like the P.O. just dumped in some pag oil and 134a refrigerant, and called it a day. not too good. if it is overcharged, your compressor could easily be destroyed, but it may be ok.
John

rrgrassi · #24 02-07-2007, 02:44 PM

The lines (small diameter)running to the the drier, where the sight glass is, should be quite warm or close to hot and the large line that usually runs across the top of the engine should be cold if the A/C system is working properly.

Basics here. Low pressure lines feel cold, high pressure feels hot, when the A/C system is running, and working properly.

Can you feel the condenser when the system is running? Does it feel warm or cold? It should be warm.

Was the system worked on recently, or rigged by someone else? You could have a plugged drier or expansion valve, or someone not knowing, could have replaced the compressor and if the lines attach separately at the compressor, could be reversed, reversing the flow of freon, like an electirc heat pump does in the winter.

Either way, it is not operating correctly, and you are looking at some big problems if it is not corrected.

1981_300sd · #25 02-07-2007, 05:02 PM

Ok I always get terms mixed up so here it goes. The condenser is next to the radiator and the evaporator is in next to the blower right?

If so, then the condenser is warm. The drier is warm when entering the drier, and seems to be cold after leaving the drier.

The system has never worked for me. Only have had the car for about 3 weeks. I have not done any real work on the AC system.

So I need to basically get the freon out, and find the trouble. Is this something that I should be able to do DIY (other than removing the freon) or should I let a shop handle it? Also one key thing that I noticed was some green fluid under the compressor. At first thought it was antifreeze, but now that I think about it, the coolant shouldnt be near there. Its not a fast leak, just saw a drip or two.

Thanks again guys.

SD Blue · #26 02-07-2007, 09:32 PM

Well, If you want to DIY, plan on buying some basic equipment. Of course first will be your own set of guages to see what the condition of the system really is. Those folks at www.ackits.com have varying starter kits and manuals to walk you through everything.

vstech · #27 02-07-2007, 09:37 PM

Quote:

Originally Posted by 1981_300sd

So I need to basically get the freon out, and find the trouble. Is this something that I should be able to do DIY (other than removing the freon) or should I let a shop handle it? Also one key thing that I noticed was some green fluid under the compressor. At first thought it was antifreeze, but now that I think about it, the coolant shouldnt be near there. Its not a fast leak, just saw a drip or two.

Thanks again guys.

Yeah, if you don't have a/c tools and knowhow, your'e gonna need a shop to do it. they will charge you less than you would pay for the tools.
if you have green liquid around the compressor, and it's not coolant from the motor, it could be leak detector oil and showing you problems with the compressor... that drier needs to come out, and I would have the liquid lines tested for debris. possibly removed and physically cleared.
keep us posted.
John