1983 300sd ac advice. - PeachParts Mercedes-Benz Forum

Mrman7627 · #1 08-07-2015, 01:51 PM

Hi everyone, as some of you may remember I just recently did my ac system and everything is more or less working no leaks proper pressure readings from both high and low sides ect. From reading other posts I see that my system may not be super super cool sense it's designed for r12. With that being said when I'm not driving or when I'm at a stop light my air gets warmer still cool ish bit not cold I felt all the pipes on my expansion valve and during the course of waiting for green light one of the pipes goes from luke warm to SUPER hot. And the expansion valve never really gets cold. Any ideas? Condensor fins are not blocked or bent I have plenty of coolant. Could my expansion valve be bad? Could my receiver dryer be not drying enough? When I got it one of the caps that keeps the innards dry was broken.

mannys9130 · #2 08-07-2015, 04:11 PM

Too much refrigerant? Aux fan not coming on? Too much oil?

Did you convert it to R134a? If so, you should start at 80% system capacity and adjust for coldest vent temp.

Mrman7627 · #3 08-07-2015, 04:18 PM

Aux fan comes on refrigerant good too much oil most is a BIG possibility. If that is the case how would I go about getting it out? Lol. Cause if I understand when u remove freon oil stays.

leathermang · #4 08-07-2015, 06:16 PM

To get oil out you pump out the refrigerant into a proper container so you can reuse it..
and take apart the system pieces and flush them...
check out the ac thread in my signature... particularly the last post by me referencing ac.com instruction on flushing...
Did you install a brand new reciever dryer when you put it together.... and then vacuumed it to get the rest of the moisture out ?

Mrman7627 · #5 08-07-2015, 06:46 PM

Alright so essentially recover the refrigerant and flush the system? Is most of the oil going to reside in the compressor? And do I need to purchase another receiver dryer? I'm trying to do everything I can to not take off the whole compressor just the pipes that connect to it compressor. After recovering the refrigerant can I flush out all the lines plus the condensor then vacuum out the remaining moisture? I did put in a new receiver dryer but when I got it in the caps that are usually on it to keep it dry were broken so it could've absorbed some moisture during shipping. And yes I pulled a vacuum on it for a good hour and then checked to ensure it held vacuum.

Mrman7627 · #6 08-07-2015, 07:30 PM

Great info on your ac thread btw.

leathermang · #7 08-07-2015, 08:47 PM

ZERO oil in the compressor if you have the R4.
That is why the ability of the refrigerant to mix with the proper oil is so important.. your R4 has NO oil Sump.... it is a Hotchkiss design..... other compressors like Sanden and earlier like York have sumps in addition to oil mixed the refrigerant...
I am sure after a little research you have determined that you should not have put that receiver dryer on with the broken seals... they should only be put on Immediately before buttoning up the system and pulling a vacuum... they have a FINITE ability to absorb moisture.... the gell pearls are UNDER oil ... and once saturated the moisture can not be gotten out.... thus the requirement that a NEW unit be installed any time the system is opened up... or had a leak....
You need to answer each question posed...Manny asked if you have changed to 134a ?
If so, how many ounces did you install ?

Mrman7627 · #8 08-07-2015, 09:59 PM

The system had already been converted to 134a before I obtained the vehicle. Before I pulled for vacuum I put 4OZ of pag 46 oil into the receiver dryer "that had the broken seals" as I had read that was one acceptable way to add oil If you were flushing the system and replacing that and the expansion valve anyway. Sense I didnt know how much oil was in the compressor "as at that time I had thought the compressor DID have oil in it" and from what I had read my car needed 8.5 ounces of oil I felt that would be a good place to start and I also had another can of oil charge with 2 oz to put in later if I found that wasn't enough. So yes converted to 134a oil put in was 4oz ounces of freon was a little over 12 ounces I don't know exactly how many ounces because each can was 6 ounces and I only used a small amount of the 3rd can.

leathermang · #9 08-08-2015, 09:43 AM

Oil amount is a real problem for all of us... there are no direct ways to measure it... it is the procedure which makes all our MB ac work much harder to get ' for sure' correct.....
If you only put a total of about 24 oz into your system.... I am pretty sure you are low on refrigerant.....you need to install refrigerant using gauges ...
but you could be correct on refrigerant and having enough too much oil for it to adversely affect your cooling.... but check your pressures first... using proper procedure when doing that... and wearing goggles and face shield....
but remember that you are shooting for about 80 percent of an R12 fill....measured in oz's.....

Mrman7627 · #10 08-08-2015, 10:46 AM

I used high and low pressure gauges low side pressure was 50 high side was around 225 if memory serves I will check again later today. And from the 134a charts I read that was about right.

leathermang · #11 08-08-2015, 10:50 AM

Most people do not have the equipment to send enough air across the condensor while the car is sitting.....
and that affects your gauge readings..
but you may have too much oil in the system as you concede... bummer if so due to only way to correct situation ...

Mrman7627 · #12 08-08-2015, 02:12 PM

It's okay though because I'm learning SOOOOOOOO much. This forum has many knowledgeable people and Noone gets angry when I ask a lot of questions ^^. So to recap. Recover freon, replace receiver dryer and flush system. Study on my car type and recheck how much oil. I know I use pag 46 and I believe my system needs 8 oz of it. But if I only put in 4 oz and when I flushed the system the compressor didn't have any oil in it as you said this type of system doesn't hold any oil in the compressor wouldn't that mean I'm short on oil? Cause when I flushed the system I flushed each individual pipe plus the condensor. Not the compresdor though as I was told that's a no no. As for freon level I looked at a r 134a chart and then added enough freon so the readings went to the advised levels "85 degrees outside low side pressure between 45 to 55 and high side between 225 and 250." Sense this system isn't made for r12 did I perhaps overcharge the system sense I used the r 134a chart and readings? As you all are advising to me that I only want to use 80 percent? Is it posdible my system is then over pressurized causing the condensor to have to heavy of a load on it?

Mrman7627 · #13 08-08-2015, 02:17 PM

I was also thinking about looking into getting a bigger aux fan and studying what I would have to do as far as differences in voltage levels and strain on the alternator or once this system goes out of commission "as the compresdir IS old" studying on doing what I believe is called a sanden conversion?

leathermang · #14 08-08-2015, 02:19 PM

Ok... just to restate...
Recover refrigerant
flush system parts which are supposed to be flushed.. not compressor ..
do not open or install receiver dryer until the very last thing you are at for putting system back together.... nice to put nitrogen through the system to begin drying...and make sure you get max use from the R/D when you install it..
Install it...and pull vacuum....
then on with things you already know...but protecting the viability of the R/D is important...
The Absolute bottle neck on ANY ac system is air across the condensor .... enough air across it can ease lots of other system problems....
So high efficiency fan is great no matter what the rest of the system is comprised of...
the Italian HF ... ' FAL " ? or some name like that... highly recommended....lots of threads about it...

Mrman7627 · #15 08-08-2015, 02:31 PM

Okay now I just got confused I started referencing a few different 134a freon charts and some are saying low side pressure should be 80? That seems way too high but I just plugged my gauges in ambient temp is 75 degrees my low side is saying 35 high side is saying 165 when I added freon initially my car wasn't fully warmed up could it not being warmed up and now testing it with it warmed up be why the readings are lower or do I have a leak? I pulled vacuum to -30 in hg n it held for an hour. But ur thread mentioned how pulling vacuum isn't enough to check for leaks. The systems been charged for a good month now so hmmmmmm. Ideas?