Proper R134A Conversion for 124?
 

Hey everyone,

My 91 300D was retrofitted to 134a sometime in 2010 by the previous owner. (a shop did it, I have a receipt in my records book). I am not sure what work they all did. I know that the fittings are now quick disconnects and there is a sticker the calls out the amount of 134a and type of oil used.

When I bought the car in summer the a/c worked well. When I went to use it this spring I found that it had lost enough charge to make the compressor not engage. I bought some 134a and charged it back up and so far its doing alright. However at 85F its not the greatest...better than nothing but not as cold as my other proper 134a system'd cars.

I know MB made 134a 124's after 1993, so I believe proper parts would be available for my 300D. So here is my question, what parts would I all need?

I would imagine:
1) Condenser
2) Dryer/Accumulator
3) Proper 134a seals
4) Expansion valve

But what about lines and evaporator? I think the compressor is OK with 134a...

This is mostly a fact finding mission as I probably wont jump on this until sometime in the fall or even next year.

Thanks!

Member ps2cho just did all that. Find his thread either here or benzworld dot org.

The condenser is no different other than the port locations. The 10pa17c Compressor requires new power steering mount, new manifold hose /w fuel cooling (if the diesels have it?) and the condenser.
My advice? Skip all that expense and do R12.

Hmm I thought there were a more improved condenser for the 134a cars...

At the moment the 134a is doing OK in the car. I think its still a bit low on charge. I keep meaning to check it when I get home from work but am too lazy/tired to do it.

I need to replace the bearings in the aux fans and probably clean out the condenser. I'm sure doing those two things will help much as well.

The only problem I have with R12 is availability and the fact that my normal mechanic doesnt do much with R12 anymore.

I had a small stock pile which went into the 420SEL..which leaked much of it out over time...

Diesels don't have the fuel cooler.

Does your 91 have a parallell flow condenser? My 91 did.

-J

This I am not sure of..how could I tell?

Look at the sides of the condenser. If you see a bunch of tube elbos it's not parallell flow.

-J

I had to google it..which led me back the forum!

Evidently non parallel flow units are called serpentine flow..


http://www.peachparts.com/shopforum/...ondensor_1.jpg

R12 is readily available on craigslist everywhere. Just buy it with intent to resell and sell it to your mechanic for $0.01.

No w124 came with parallel flow. They are both tube and fin. We have the worst and that's why our conversions just plain suck. Its commonly thought that the later condensers were bigger or better, they aren't; they just changed the location of the hoses and added the more powerful 23/25 amp twin fan assembly with shroud.

Here is the later model condenser -- tube and fin:

http://www.w124-zone.com/downloads/p...ofit/cond1.JPG
http://www.w124-zone.com/downloads/p...ofit/cond2.JPG

Do you know what oil they put in? If they put ester oil, re converting is as simple as pumping down and recharging with r12.

I'd be happy to help you with it as I have all the equipment to do it

I was just looking in the EPC...Everything is the same from my 91 to the 95 E300D. Same part number for the evaporator, compressor and condenser. Damn.

Its on the label. I'll have to see. I for certain would need to replace some seals though. It was charged before winter hit and after...not enough pressure to kick over the compressor so clearly a leak somewhere. I would definitely want to make sure everything is done proper before putting some R12 down there.

I was down that path with the 420SEL. I *thought* everything was taken care of but...I still had to sink 3 cans in it a year later...

Charging with nitrogen is a whole lot cheaper than r12. Pressure testing IMO is the best way. 180psi solid for 24 hrs = victory.

I'd throw 1 can of 134 with some dye in it and check the leaks with a black light. Once it cycles a few times the dye will show.

I charged my car 4 times with nitrogen before I found every last leak. My ac is still ice cold.

Does your 300E have the 10P15C or 10P17C compressor?

I found this comment on the two:

I am almost thinking about researching swapping the 15 out for the 17. My 420SEL has the 17 with R12, which does very very well.

However, keeping the 15, I think eventually that is the path I will take.

Replace every seal.
Remove the evap, clean it out.
Remove the condenser, clean it out.
Replace the schrader valves. Actually it has quick-connects on it now..
Pressure test. Is there any reason you chose 180 psi as opposed to something higher?
Verify
Verify
Charge with R12.

Today on the way up I stuck a thermometer in the center vent. 72F outside 74% humidity, at highway speed, I got about 48 at the vent. So a 24F temperature differential. Not horrible, but probably not as good as R12 or the ES-12A that I have in the 190E. I will get another reading on the way home today where it will undoubtedly be warmer. Tomorrow I'll be in the 190E so I can get that data as well.

Based on the charts provided in the 88-608 pdf:

At my conditions I should expect to see:
40% - 90% (Humidity)
260 PSI - 320 PSI (High)
14 PSI - 30 PSI (Low)
40 F - 46 F (Vent)

I believe there is a 10-15% efficiency loss with 134A...so my numbers were on par with what would be expected?

Removing the evap requires dash removal.- Not worth it unless you are replacing it.
Replacing seals is time consuming but very straight forward.
I would try and unscrew the quick connect and revert to the original setup. Its one less conection ie. place to leak. Also, a mechanic will think the charge is r134

I chose 180psi because I believe that is a reasonable limit to the low side. Any and every leak will show up at 180 psi. There is no need to go higher.

If it hold dead-nuts 180psi for 2 days then it is good.

Replace receiver/drier, pump down. Fill with nitrogen, pump down. Repeat 3 times.

If I remember, 3 cans of r12 from ebay is the perfect amount. I believe they where 12 oz each. The w124 is 2 lbs I believe, but there is a bit of waste in the can and in the hoses etc.

Great find! Offtopic I suppose, but my 91 350SDL has the 10P17C. The parts listing said that compressor was also used on the 6 cylinder R129 cars and W140 Diesels, which would have been R134a from the factory.

-J

Yeah, the OM603.970 was the only diesel to get the 10P17C. All other cars eventually got it it looks like. I wonder why the other OM60x series diesels never got it...

According to the PDF charts :

At 80F ambient, vents will be 43-59 F (40% - 90% humidity)
At 85F ambient, vents will be 47-66 F (40% - 90% humidity)

Humidity is in the 60%s right now.. so I would be a just a bit left of the middle..so.. maybe 50F if 80F ambient, 55F if 85F ambient.

Damn, that just seems crappy. Why did they not give this poor engine the bigger compressor?

I wonder if my 190E has a 10P17C on it... The motor was a transplant from a 300SEL...

my 300e has the 15 compressor and is very cold. Only when stuck in traffic on a 95+ degree day does the ac system become marginal. Even then, its ok.

Are those temps based on 134?

http://www.peachparts.com/shopforum/tech-help/321602-i-have-conquered-w124-air-conditioning-now-kneel-2.html

Here is the thread. Corrections are: I do have the 15 compressor, and I charged with nitrogen to 200psi.

The numbers came off the charts in the PDF. I would believe they are for R12.

You have to realize that when the car is running it starts to recirculate already cooler air. Reading back on my old thread, 30* drop is what you would be looking for.

by reading here, it seems that the only different bit is the condenser fans, I know my car is R134a, has twin fans at the front and I get numbed fingers from the cold - so much that I have to dial it down to 78F to be comfy.

As our condensers arent worth it, I believe it would be mighty beneficial to use a multipass condenser or even a refrigerated dryer (seen that in porsche once)

James, it would be MUCH more time and cost efficient to simply reverse convert to R12. Just get a new receiver drier and an o-ring kit. Break all lines and flush them all. If you don't have a flush gun use brake kleen. Blow out the lines thoroughly, preferably with an inert gas, but compressed air if you have nothing else. Rinse the compressor with mineral oil, not solvent.

When you put everything back together distribute the oil in several components and put the r/d in place as the very last step and be ready to evacuate as soon as the r/d is in place. Then charge with R12.

I've reverse converted a number of vehicles with great success. With R12 prices being as low as they are these days, this is a very practical thing to do and will not only save the cost of all those parts, but offer less chances for problems.

Hope this helps.

There are other differences including the higher capacity 10P17 compressor. The 124 cars designed for 134 seem to work well, retrofitting an earlier car is not a good plan. It is a very poor candidate for 134 conversion.

I agree, a properly done R12 conversion seems to be the best approach. Proper being everything resealed, thoroughly cleaned, flushed, evacuated etc.

I was looking into these 134 cars. According to the EPC, the 95 E300D and my 91 300D share the same, evap, condenser and compressor. It would seem MB did not really do much in the way of 134a (at least on the E300D, I didnt look at the rest of the cars)

I do like the quick-connect ports though :( will miss them when its converted back

There were three different compressors used on the 124 cars, two 10P15's and one 10P 17. You never know what you're gonna get. I think that most all the late cars had the higher capacity 17's while very few early cars had anything except the 15's.

Based on what I saw in the EPC. The diesels all got the 15. Im not sure what the difference betwen the 10PA15C and the 10P15C is.. but I know all the diesels except the 350 got the 15. The 350 got the 17.

The 17s made it to the gassers..later on i think. not sure who or when.

Im about to leave work, we'll see how it does! Thanks for all the help everyone! 80F / 70% humidiy!

Best I got was around 53-55 at the vent or so. 85 degree ambients...which is OK performance. It falls in the range according to the chart..

Tomorrow I'll drive the 190E which is charged with ES-12A (not Larry's favorite but I was in the middle of suspension rebuilds and really didnt have the funds/time for a proper install. I think if I ever get around to it..I'll mate the 10P17C compresssor for some extra headroom ;) But I'll get numbers and see. I am going to bet it will do better than 134a. I know it does ****ty at idle..

Proper? You make the call, but for ten bucks worth of refrigerant you can evacuate, refill and chill.

No replacing anything else: no new seals, no new dryer, no new oil---nothing.

Next year, add another can; mine was done Feb 2012 and just added another can last week.

Did the research - see:

Propane(R-290)&Isobutane(R-600a) 60/40

My posts:
AC compressor will not engage after evacuation - Benzworld.org - Mercedes-Benz Discussion Forum

Charging with propane...how? - Benzworld.org - Mercedes-Benz Discussion Forum

A very sad day indeed - should I keep it or sell it at a low price - Benzworld.org - Mercedes-Benz Discussion Forum

Well its that time of year again! - Benzworld.org - Mercedes-Benz Discussion Forum

Not my posts:
Charging with propane...how? - Page 2 - Benzworld.org - Mercedes-Benz Discussion Forum

R-12 vs Propane vs R-12a (time to recharge A/C) - Benzworld.org - Mercedes-Benz Discussion Forum

Using propane instead of R-12 for A/C - Benzworld.org - Mercedes-Benz Discussion Forum

AC problem solved with propane- Did I plan for suicide - Benzworld.org - Mercedes-Benz Discussion Forum

Other stuff
And apparently you do not have to change the drier with this either

Pasted from <http://www.firstfives.org/faq/AC/ac_repair.html>

This gives charges of approx. 40-45 % of R 22, R 12, R 134a or R 404A charge in grams, according to the data from table 1, which also corresponds with empirical values.
hydrocarbons21.com

Per ghg: [60% propane / 40% isobutane works better.. pressures are correct

Pasted from <http://yarchive.net/ac/hydrocarbon_recipes.html>


To evacuate or not when going from R-134a to R-290 & R-600a? Yes.
Per ghg - paraphrasing of course: there is a possibility of the R134a breaking down to acids when exposed to moisture. Since propane could have moisture then it seems necessary to evacuate. If not evacuated then moisture level should not exceed 10-20ppm; however, if it is evacuated the moisture level can go up to even 1,000 ppm.

1100 grams R-12 - - that is what our w124's call for. And then I calculated the rest:

38.8 oz. R-12
40 - 45 %
15.42 - 17.46 oz.

And @ 60/40 by weight
Propane/Isobutane (oz.)
9.25/6.17 - 10.47/6.98
If 8 oz. of Giga then 1.2 oz. Propane + 6.8 oz. of Iso-Butane
Need additional 9 oz. Propane

• GigaPower Fuel 110 Gold - This is the one I chose and your calculations may differ based on the refrigerant you choose.
Giga 250 grams = 8.818 oz. Then 1.3 oz. (R-290) + 7.5 oz. (R-600a)
Need to use 7 oz of the R-600a and then an additional 9.2 oz (R-290).

Can (GP250G) is acutally 7.76 oz. --- only need 7oz and then 9.2 oz of (R-290).

Thanks,
cool in atl