84 euro 240d with parallel flow condenser and r12

[Rjinaz]

I have a 84 euro 240d which I acquired two years ago. The car came with an aftermarket ac setup. This past summer I overhauled it with a new sanden 508 compressor, expansion valve, reciever drier and a large parallel flow condenser and charged the system with r12. This combination has worked very well for me. I live in Phoenix. In the mornings ambient temps are in the low 90's, but I can get 40 degree air out the center vents on high fan speed and even in the mid thirties on medium speed. Coming home today the ambient temp was 112 degrees. Despite this I still got 50 degrees out the center vents on high fan speed and right at 40 degrees on medium fan speed. The one problem I have is that the ac system seems to work better at low driving speeds(20to40mph) as opposed to lets say 70mph where the air simply isn't as cold, not to mention the fact that if I drive at 70 for an extended period of time the blower speed slows down on its own an starts putting out warm air. If I return to slower driving , blower speed starts to pick back up and air starts to get colder again. Any Ideas as to what is going on here?

[SGT John]

BUMP for a good question. I am considering trying to throw a PF condenser in my car and if this is common, then I don't think I want one!

[Mister Byrnzoil]

when you are going 70, can you feel the compressor clutch engage and disengage?

[Rjinaz]

I believe the compressor is staying on all the time as I don't feel it turn on or off.

[Ken300D]

It is possible for the system to freeze up the evaporator if the compressor does not cycle properly. When it freezes up you get reduced air flow through the evaporator and the cooling effect actually decreases, even though the evaporator is a block of ice. Turning off the A/C when this happens often results in fog coming out the vents as you go along.

The other thing that can happen, and I believe could be your problem, is excessive outside air coming into the system. You may want to manually force the recirculator door to cause only recirculation of inside air during the hottest months. That's what I need to do on my 300SD, but have not determined how to do that yet.

Ken300D

[fireman1073]

mono valve could be letting some coolant through when engine is running constant rpm's at highway speed

[dmorrison]

A few comments.

Good AC working at low speeds then poor at high speeds. I would say is the mono valve. At higher speeds the very hot water is forcing it's way past the old mono valve.

As mentioned above the system could be freezing. But in PHX, especially now, with the hot dry air, I 'm not convinced. If it is freezing then the evaporator temperature control unit is faulty.

We need a few bits of information.
After market system, how are the controls setup? Are you running the AC controls in what we would consider "Max air". The fan is at High and not in a automatic control mode. Is the temperature set to "maximum" and not controlled by a temperature sensor in the cabin?
If your system is operating this way then Yes consider physically closing the "main system flap" in the system. This will close off the outside air. fist try placing something over the windshield cowl vents on the outside front area of the windshield. This is the outside air entry point. Block these 2 openings to test the outside air theory. If you notice a change then consider manually closing the "main" flap.

Fan speed. You need to check the fan bearings and brushes. Both of these can cause a fan to slow. Is the fan speed actually slowing, or is the air being blocked due to the evaporator freezing? If is slowing down then either bearings/brushes or its your AC control.

OK now for the really big question. We want pictures of the Sanden 508 compressor mount and how it is done.
Lots of members would love to replace the G4 unit and this may be a good option. Lots of pictures and diagrams if you can get them.

Dave


We really would like some pictures of the Sanden compressor mount

[Rjinaz]

Thanks for the responses. I'll see if I can get some pics up at a later time. You'll be interested to know that while watching football this morning I heard a big bang and a loud hissing coming from my garage. When I ran out to see what is was I found my #10 hose connected to the compressor had blown right off the fitting spraying refrigerant everywhere. When I charged the system with r12 three months ago I used 48 ounces, more than the usual 38-40 thinking that with a larger pf condenser, it would need more. The low and high side pressures seemed to be ok. I believe now however this was a mistake on my part. Could having more refrigerant than necessary caused some of my problems not to mention the hose blowing off? My reciruclation flap appears to be non functioning, stuck in the closed position. The climate controls are the standard 240d controls.

[Ken300D]

Yes - some way to mount a different replacement compressor would be great and benefit a lot of people. Did you have to use a different mount bracket? If so, where did it come from?

Did you measure your high and low charge pressure with a gauge set? If not, I'd recommend you invest in a set such as found on EBay. That way you are not guessing the charge as much - although some would say still guessing to some extent if you didn't measure out a volume of refrigerant - but with custom components that's hard to do.

How hot do you estimate the garage was when the hose blew?

Ken300D

[Rjinaz]

It does get extremely hot in the garage here in Phoenix, but I doubt that had anything to do with the hose blowing off. The mounting bracket came withthe car andis definetely unusual, a one off type of deal. When I went to get new bushings for it every mercedes shop and mechanic said the same thing "what is that" or "I've never seen that before" I ended up taking some sway bar bushings I got from pep boys and grinding them down so they would fit. Right now I am thinking about getting some more r12 and recharging the system only with less refrigerant and being really careful with the pressures. I'm a little gun shy however because I'm not quite sure what exactly caused this. I've used the ac every day for the last three months without a problem except for those mentioned above. Now I'm thinking there may be a more serious problem with the system.

I also have an 84 euro 240D with aftermarket air. There IS no monovalve. I also believe that the problem is outside air. with 40 degree vent temps, I don't think that there is an evaporator freeze going on.

I personally would not go to a different compressor. The Sanden is REALLY tough to beat. One of the advantages to your car is the simplicity and effectiveness of this a/c.

What are your pressures, and your vent temps at particular outside temps?

[Rjinaz]

I don't recall the pressures when I charged the system back in may, the vent temps get to around 40 degrees on high fan speed and in the mid to upper thirties at a lower fan speed when ambient temps are in the 90s or below. In lets say 110 degree weather, vent temps are around 50 degrees high fan speed and lower 40s at a slower speed. I agree with you larry about the sanden compressor. I have been very pleased with it. Another thing I noticed is that vent temps at the outer two vents are not as cold as the center vents. Do you think this to is caused by outside air geting into the system?

[Rashakor]

50F air vent with 115F outside. Darn!!! i get 50F with 95F outside.

We need pix of the Sanden Compressor!!!!!!

I don't think that the difference in vent temps on the outside vents is an indication of outside air, but you need to try to determine if this is the problem. My euro aftermarket air, which I fully expect is just like yours, has a screwy setup of the control levers. Experiment with them to see if there is any position that will give you different vent temps.

The Sanden compressor mount is quite simple. It is a mount that bolts to the lower left of the block, mounting the compressor with four bolts to the mount with two in the back and two in the front. It mounts the compressor in a solid position and uses and idler for belt adjustment.

I don't have a digital camera from which I can download to the computer, or I would take a picture of one of them. If both compressors weren't in place on these cars, I would bring one of them with it's mount to the tech session to show you, but I don't want to blow the charge on either car.

[Rjinaz]

Here are some pics of my sanden 508 compressor. They are not the greatest, buy you can get an idea.