124 expansion valve

I will be getting my R134a conversion kit tommorow. It was recomended that the expansion valve be changed as well. I plan on doing all this myself.

For the 92 300D 2.5 (124), I understand the expansion valve is around the firwall. But where exactly is it and what do I have to remove to get to it? Thanks in advance...

[jeffsr]

It is not necessary to change the expansion valve for the conversion. It is recommeded, but not "necessary". You can see the valve at the firewall, I am not sure it can be separated from the evaporator w/o removing that piece. This is a job you do not want to tackle. The conversion is a compromise of sorts, so there are other components that would need replacement for max efficiency, ie. compressor, receiver/dryer and a larger condenser. Keep it simple and see what you get without swapping a lot of parts.

Brother of The Benz,
Johnson, I don't know where you got all of the data that says you must change componnents of your A/C system to convert to R 134A.
My 1987 W124030 (300E) is cooling using 80% of the original R 12 refrigerant capacity in R 134A.
I purchased my conversion kit from K Mart here in Houston.
I didn't flush or change the oil in the system; just added the oil charge that came with the kit plus a "Hot Shot" suppliment with a dye for detecting leaks and a stop leak to seal minor leaks.
I evacuated the system by a commercial refer shop.
I pumped the system using my own vac pump. I'll not get into what pressure I pumped to, just that it was adequate.
The system is cold enough to make your left hand uncomfortable with the duct blowing on my left hand on the steering wheel.
I know there will be flak over the way I did mine, but that's the way Interdynamics instructs you to do it.
I purchased a capacity gauge to help finish charging the system.
K Mart had the gas on sale this week for $3.50/can of 12 oz.
Do your self a favor and do it the simple way.
Happy Trails Beep Beep from The Spiderman in Houston!!!

Hello Donald,

I got this R134a conversion kit from Tom. From what I heard from a lot of people that its best to replace this and that and that, so I just went ahead and ordered it. The AC parts came to $116.00.

I just got it all in the mail today.

Where did you get HOT SHOTS from? I tried to look for it but did not have any luck. I didnt know about your method till now, I dont want to cause any inconveince and return all these parts, so I will just go ahead and do the conversion.

BTW, check the MBCA forum under bad luck, need opinion. First thing I need to do, is get the oil pan fixed so my d*mn car can run, AHHHHHHHHAHHHHHHHH.

[jcyuhn]

Hi Johnson -

Since noone has answered your original question, I'll give
it a shot.

The expansion valve is under the hood on the 124, right
at the rearmost firewall. It is next to the power brake
booster, toward the center of the car. It's quite easy to
see, though working on it would be a different issue...

In simple, non-technical terms: Find the brake master
cylinder. The booster is the big pie-plate thing to which
the master cylinder is mounted. Look toward the center of
the car and down a bit. The expansion valve is a block
of metal about 2"x2" square, and perhaps 1" thick. It has
two metal lines going through the firewall into the
interior of the car, and two lines connected to the
opposite side which head toward the front of the car.

The two lines heading into the inside of the car are in
fact the inlet/outlet of the dreaded evaporator. The other
two are the high side/low side lines to the compressor.

- Jim

Hello Jim,

I found the expansion valve, the new problem is how do I change it?

I can barely get my hands in there let alone my tools too. From what it seems, I would have to remove a lot of hoses and stuff to get in there. ALso do I have to remove the instrument cluster from the inside of the car? Any tips? Thanks...

[jeffsr]

Johnson, did you read my response to your original question?
Leave it alone, unless something is wrong with it. The expansion valve is the least likely piece of an A/C system that will improve efficiency. Get a bigger condenser or a higher capacity compressor if you are bound and determined to spend money on this project.

Hello Jeff,

I did read your responce. Its just that when I called the dealer and asked them for a R134a conversion kit, this peice was recomended and sent/billed as well.

Since its laying in the garage, I was going to replace it. But now after examing the location and situation, I think I will just leave it alone. I replaced the drier bottle and O rings yesterday and will have it recharged next week.

If all goes well, I will just keep the expansion valve for future repairs or just return it.

Since I had an AC leak before and the system wasnt working, this piece MIGHT be related, I will just hang on to it for a few days after the conversion. What do you think?

[jeffsr]

You may have the dreaded evaporator problem. In which case the replacement of that part will give you access to the expansion valve. It requires removal of most of the dash and is labor intensiveas well as $$$ if you are having it done. See how the conversion goes and hope that it isn't the evaporator that's leaking..

Jeff,

I hope not too. If it is the "dreaded evaporator problem" thats leaking freon, I will just keep topping it off as needed.

With R134a, its cheap enough to do that compared to R12 at $90.00/lb or so.

I hope the AC works after I charge it this week. I will keep my fingers crossed. If I it doesnt work, I will have to take it to the dealer to get it fixed. The AC system on my car from what I understand (and experiencing), is complicated. It could be compressor, AC clutch, low freon pressure, faulty pressure switch, fuses, relays, bad auxillary fan, and other parts, erratic idling can also cause this problem (which I also have, grr)

It could be a whole lot of different reasons, without a fault code reader, all I can do is replace part by part until it works, which I dont plan on doing, lol. Thanks for your help.

Brother of the Benz, Johnson
Whoa, Stop, Turn around and go the other way.
Inconvience poohy, Return the parts and save the mooh la.
Johnson you DON'T have to make these part changes.
If You HAVE started, you should have a good set of tubing wrenches to keep rom rounding over the edges of the aluminum fittngs.
I don't know what else I can say to help you, except I apologize for not getting to you sooner.
But, PLEASE don't make this conversion as you are doing.
The "Hot Shot" charge was purchased from K-Mart here in Houston. It cost $9.95.
If you think you have a faulty compressor, Buy the R-134a pressure gauge for the low side pressure. This will tell you if the expansion valve in operating properly by having pressures lower than head pressure and in the "BLUE" scale if the R-134a is charged to the proper capacity.
Normally I don't change the high pressure fitting to the R-134a style so I can attach either my old R-12 high pressure gauge or my vac pump to the old manifold.
Attach a R-12 high pressure gauge set to the high fitting to test the compressor.
UNhappy Trails Beep Beep from The Spiderman in Houston!!!


[Edited by dlswnfrd on 06-03-2001 at 09:37 AM]

Donald,

You are not too late. All I have changed so far is the drier bottle and o-rings for it. I have not touched the expansion valve yet and dont plan to.

I will try to charge it with R134a next week and go from there.

I have had people tell me about hot shots but I couldnt find it, it will be my luck that next time I go to Kmart I will see some on the shelf, lol.

Thanks for your help Donald, im sure more problems are to come with my car, always my luck, grr...

Johnson

Brother of The Benz, Johnson
You did good replacing the drier reciever, it always helps when servicing an older unit.
But STOP at this point and return the balance of the parts.
Beg, borrow or rent a vac pump and gauge/manifold set to evacuate the system.
When making the change over keep the R-12 high pressure service port as original for in that way you can use older R-12 gauge/manifold for pumping the system down from the high pressure port.
Your change over kit should have the service /charging hose for the low pressure side.
All that you should purchase now is the charge capacity gauge/hose and fitting.
If you can't find the "Hot Shot", contact me on my E-Mail and I will get it for you here in Houston and mail same.
I pray someday your problems all are corrected, for you have had your share.
You are the Classic Mercedes Benz Lover.
Happy Trails Beep Beep from The Spiderman in Houston!!!