W124 A/C in hot climates? Who can compare? - PeachParts Mercedes-Benz Forum

ps2cho · #1 08-04-2015, 05:10 PM

Does anybody here live in a climate over 100F in the summers who can give some comparison vent temperatures?

I find I'm 110F the cabin never gets cool. I get about 60F from the vents at speed but at idle it'll creep up to 80F.

I may just need to evac and recharge by weight instead of pressures, but I wanted to see some comparisons.

I am running r134a right now and I installed two spal hd aux fans to increase my cooling at idle.

lsmalley · #2 08-04-2015, 05:27 PM

Are you positive that there is zero coolant passing in to the heater core? We're at 103°F today. I'll go out and get some readings for you: I use center vents, both aux fans on high speed, with infrared temp reader.

jcyuhn · #3 08-04-2015, 05:56 PM

It should do somewhat better than that. Are you sure all the vacuum pods under the dash are functioning 100%. In particular, the recirc pod has three positions - 100%, 80% recirc, and 100% recirc. The small vacuum chamber that pulls it from 80% to 100% recirc tends to fail first, so you don't necessarily notice the difference. But drawing in 20% outside air will noticably degrade the ac performance. It's easy to check with a handheld vacuum pump/gauge.

Phillytwotank · #4 08-04-2015, 06:07 PM

97* air temp
33% humidity
99* heat index
Cruise control set at 75mph on I77 NB for 33 miles
AC on
Recirculate on
Fan speed low
46* on the lateral vents

ps2cho · #5 08-04-2015, 06:14 PM

Maybe you are right...I know I checked my vacuum pods about 6 months ago (i replaced them all 2yrs before) and they were fine but I was getting air out the defrost vents which I read should not be happening. I guessed it could be the vacuum bypass unit that all the hoses attach to. Maybe in addition to the defrost vents not closing it could be leaving me at 80% instead of 100%...

Hit Man X · #6 08-04-2015, 06:33 PM

The little elbows off the vacuum tree have become a leak point on my new to me 300E. PN - 201 805 01 03. I recently replaced all of the pods and did about 42°F from center vents on 134A down the freeway with the fan on low speed. I am just running 134A for now until I replace the entire system. Probably will dump it and slip in 152A as the pressure curve is nearly the same as R12. SAE has a really interesting research paper on it. Worth the read.

My city creeps up more as the fan clutch is dead (last check was about 59°F at idle when it was just under 100°F), so the aux fan is wired for low speed always currently. I swapped in a 16" Spal (barely fit, I mean really tight) and since my tensioner is dead it loaded my alternator down too much causing big time belt slip. M104 mechanical tensioner time for me.

30102049 is the part of the Spal I wedged in there. Just this on high speed moves a pile of air. I plan to use it on low speed with A/C and my 91°C trigger (with a resistor) in conjunction with the aux fan as normal AC pressure driven. Then use high speed at 99°C. Zip me a PM with your email and I will send a few photos of the fan mounted.

Rock Auto has a listing for a parallel flow condenser for the 300E from about 1991 on. The AC hoses are slightly different, so you can buy a set from a later car or just modify yours accordingly. I feel this is the only way you will receive adequate performance from 134A in the 300E. Honestly, I would do it even with an R12 system.

I do notice if the car has sat in the sun for an extended time, it will take a LONG time to cool back off. Utilize one of those windshield reflectors and park toward the sun to reflect what you can. Drive with the windows down for a bit when you first get the car going. It is easier to cool 100°F air than 150°F air.

I am in Texas so you know.

lsmalley · #7 08-04-2015, 07:34 PM

Ok....outside temp is 108°F, car idle, engine temp at 85°C, a/c on w/ low speed fan I'm getting 61°F at the center vent. Same setting with hi speed fan I'm getting about 58°F. Driving at 30 mph, a/c with low speed fan I'm getting 43°F. Same setting with hi speed fan I'm getting about the same. My conclusion: there must be something amiss or it's just the way the insulation is. Ps2cho, our climate is exactly the same. I let my car sit out in the sun for 45 mins before doing the tests. When I got in my car I clocked the inside cabin at 129°F. I'm now wondering if making some sort of insulation around the blower motor plastic capsule would help. While these cars are great, at the time of production they used and came up with things that were available to them at the time of production. Fast forward 25 years and there are new ideas and material that go into production. I would say even a 2001 base model Kia would be better at cooling under the same exact scenario.

engatwork · #8 08-04-2015, 07:50 PM

What year is it? Was it designed for 134? If not maybe update components? You should be cooling better than you are.

ps2cho · #9 08-05-2015, 12:18 AM

There are no parallel flow Condensers for any 124. They just changed the port location and made it very slightly bigger.

I think I really need to just rebuild the system and go back to r12. I already have a new compressor and evaporator...the evaporator replacement is a bear of a job though.

Hit Man X · #10 08-05-2015, 12:37 AM

Check part 7-4502 at autozone. I guess I should have stated it is an aftermarket part.

Looks PF to me.

gatorblue92 · #11 08-05-2015, 05:06 AM

FWIW I have found that the A/C in the early W124 cars is a lot weaker than the later cars. Both my 87 and 91 had A/C that would keep you from being miserable but would never really cool the car down completely. Both were originally R12 converted to 134a. My 93 is a 134a car and it will freeze you out in short order.

ps2cho · #12 08-05-2015, 11:32 AM

Quote:

Originally Posted by Hit Man X

Check part 7-4502 at autozone. I guess I should have stated it is an aftermarket part.

Looks PF to me.

When I Google search parallel flow that looks like the same serpentine condensers that are stock.

I found a used vacuum changeover unit for $21 since a new one is $160!

Should be here this weekend so maybe that will help.

Hit Man X · #13 08-05-2015, 02:38 PM

You can always order it and if it is is not a PF, just return it.

ps2cho · #14 08-05-2015, 03:47 PM

Well I already have a new condenser so it should be fine.

I'll report back with the new vacuum control unit

lsmalley · #15 08-05-2015, 04:02 PM

Quote:

Originally Posted by ps2cho

When I Google search parallel flow that looks like the same serpentine condensers that are stock.

I found a used vacuum changeover unit for $21 since a new one is $160!

Should be here this weekend so maybe that will help.

Did you test your original change over unit? How would you know if it's bad or not? I have an extra one, but my original seemed to be ok so I never put it on. Please post the results after you get everything back together to see if it helped.