Recommendation Sought A/C Repair 85 - PeachParts Mercedes-Benz Forum

rmmagow · #1 06-01-2011, 11:27 AM

300D. Looks like it was messed with relative to a 134 conversion. I also can't seem to get the center vents to open.

I am in RI, I do not have the time to play deep with my A/C. I'm asking if some board members might know of a reliable shop that will work on the A/C without totally ripping me off. I am prepared to go to $1500 to have this thing fixed and blowing cold. I do want to stay R12 so the "Fix" would be find and repair leaks, pull a deep vacuum for me and I'll recharge. I have the R12, a 609 cert and manifold charging setup for r12. This is not cast in stone. If a full rebuild is called for I'd go for a nice big cross-flow condenser and R134.

I would like to fix the center vents first though. No Air blows no matter what button is pushed. I'm going to venture into the back of the dash and see if there is an obvious issue, bad vac thing, disco'd vent pulls etc. My heat works good and regulates properly which I hope means my ACC control box might be OK.

My 300D has had to be pressed into full-time 100 miles a day service. The heat really kills me and I'd sure be a happy camper if I could get some relable cold out of the A/C. Car has 181000 miles now and since it's not a rust bucket, I'd like to drive it for the rest of my life.

SD Blue · #2 06-01-2011, 02:17 PM

Quote:

Originally Posted by rmmagow

300D. Looks like it was messed with relative to a 134 conversion. I also can't seem to get the center vents to open.

I would like to fix the center vents first though. No Air blows no matter what button is pushed. I'm going to venture into the back of the dash and see if there is an obvious issue, bad vac thing, disco'd vent pulls etc. My heat works good and regulates properly which I hope means my ACC control box might be OK.

Are you saying the blower doesn't work or just that you can't get air flow from the center vent? Also, Is your compressor kicking on when the a/c is switched on?

If you are just having a center vent problem, it would be best to DIY the repair or it will be a significant charge to have someone dig into that.

Also, you can check the monovalve to see if it is closing by putting a meter on it and see if you get a voltage change when the a/c is enabled. (The ACC controller grounds one of the pins.)

rmmagow · #3 06-02-2011, 12:28 PM

Quote:

Originally Posted by SD Blue

Are you saying the blower doesn't work or just that you can't get air flow from the center vent? Also, Is your compressor kicking on when the a/c is switched on?

If you are just having a center vent problem, it would be best to DIY the repair or it will be a significant charge to have someone dig into that.

Also, you can check the monovalve to see if it is closing by putting a meter on it and see if you get a voltage change when the a/c is enabled. (The ACC controller grounds one of the pins.)

The blower does work since I do have good heat and defroster. I'm think the monovalve is fine since no heat flows when I have the temp wheel cranked to cold. In a previous post someone mentioned I should get at least air from the center vents even if the A/C is not working. Compressor clutch does not engage but I think that's more because I have no refrigerant left in the system than any other problem. I'm not actually too lazy here but have no real time to put into the car other than "important" maintenance. In truth, I'd like to fix it myself and may well just go buy a vac pump to get ready. I did just recently buy a tool for injecting dye into an A/C system. Even though I can't pull a vacuum, can I put in a little 134a to trigger the compressor, then some dye to see if I can find the leaks or will I be risking an over pressure situation here. Ideally, I'd disassemble the system, blow it out, put in all new seals, pull a vac and see how it holds. There's just a lot of work involved here and I don't really want to be breaking something big when maybe all is good except for some leak someplace that might be easy to fix for a pro.

engatwork · #4 06-02-2011, 12:47 PM

You can go in through the glove box hole (with the glove box removed) and rig it where it will stay open all the time. You can then use the direction louvers to close it off if you want it closed off. It seems the vacuum pod that controls the center vents go bad and they are now in the default closed position. I put a thread up on here a few years ago in regards to how to do it.

Ol'Smokey · #5 06-02-2011, 10:22 PM

$1500!!! I'm amazed at how much people on this site fork over to fix a/c systems on 25 to 30 year old cars. And then when the motor or trans go out the car inevitably turns in to a parts car.

1980sd · #6 06-02-2011, 10:44 PM

Don't know about an '85 but on an '80 the center vents are only open when the system is set to cool. With heat or defrost no air comes out the center vents.

rmmagow · #7 06-02-2011, 10:59 PM

Quote:

Originally Posted by 1980sd

Don't know about an '85 but on an '80 the center vents are only open when the system is set to cool. With heat or defrost no air comes out the center vents.

Temp wheel set all the way cold. All heat stops but center vents blow nothing even with blower set to high. I know I have some underdash issues, grounds etc. I'll check the vac connections and mityvac a few things. My center vent actually don't have the turn to close feature, I'm not sure the center vents are supposed to have this. Center vents are slightly different than the side vents right??

rmmagow · #8 06-02-2011, 11:02 PM

Quote:

Originally Posted by Ol'Smokey

$1500!!! I'm amazed at how much people on this site fork over to fix a/c systems on 25 to 30 year old cars. And then when the motor or trans go out the car inevitably turns in to a parts car.

Most of my cars are parts cars that I have to use every day. The old 123 will get an easy 250,000 miles I'd guess. It runs well, no smoke, tranny has no flare and mostly it's in good shape. I'm an old guy, this is my last toy.

1980sd · #9 06-02-2011, 11:20 PM

Quote:

Originally Posted by rmmagow

Temp wheel set all the way cold. All heat stops but center vents blow nothing even with blower set to high. I know I have some underdash issues, grounds etc. I'll check the vac connections and mityvac a few things. My center vent actually don't have the turn to close feature, I'm not sure the center vents are supposed to have this. Center vents are slightly different than the side vents right??

Not sure if it'll help because I have ACCII with defrost, bi-level, auto hi, auto low and off.

The center vents ONLY open when on auto hi or auto low with the wheel set to cool or when the wheel is adjusted from heat to cool. There are eight or nine "steps" which have different blower speeds, duct flap positions, heating water valve positions, etc. and there are only 2 (I think) steps that have the center vents open.

My car has the servo so it's a different system from yours but I imagine the basic functioning of it isn't that much different.

The center vent deal had me really confused until I figured out (Through a lot of reading and tinkering) what was going on.

Yak · #10 06-03-2011, 06:58 PM

Quote:

Originally Posted by rmmagow

Temp wheel set all the way cold. All heat stops but center vents blow nothing even with blower set to high. I know I have some underdash issues, grounds etc. I'll check the vac connections and mityvac a few things. My center vent actually don't have the turn to close feature, I'm not sure the center vents are supposed to have this. Center vents are slightly different than the side vents right??

Sounds like a vacuum issue for the center vent flap. The center flap should open with ACC III and cooling. You're saying your center vents don't have the rotate-to-expand-the-butterfly closure thing? No Nike-like "swoosh" symbol on the nozzles?

Get a probe thermometed and put it in the outboard nozzle. Measure exhaust vent temps. Even with no air out the center you should get cooling from the outboard vents.

rmmagow · #11 06-03-2011, 08:14 PM

Quote:

Originally Posted by Yak

Sounds like a vacuum issue for the center vent flap. The center flap should open with ACC III and cooling. You're saying your center vents don't have the rotate-to-expand-the-butterfly closure thing? No Nike-like "swoosh" symbol on the nozzles?

Get a probe thermometed and put it in the outboard nozzle. Measure exhaust vent temps. Even with no air out the center you should get cooling from the outboard vents.

Yeah, they do have the swoosh, and no they don't close. I bet the flaps are broken inside. My passenger side vent was broken like that and so is the driver's side. I have some spares lying around and will perform a swap. Center seem a little different size but I'll figure all this out. No cooling, no freon. Pressing on schrader valve no gas comes out. Pretty sure entire system is empty. I think I'll invest in a vac pump and play around trying to find any leaks. I have a dye gun but maybe a sniffer would be better.