123 with a Sanden and R134a: vent temps - Page 2 - PeachParts Mercedes-Benz Forum

theref · #16 07-26-2013, 11:10 AM

Will look at those components.

ROLLGUY · #17 05-11-2014, 01:18 AM

After installing the wiring and relay to run the condenser fan while the compressor clutch is engaged (not waiting for the thermal switch to do it's job), I am having lower vent temps sooner. Check out:
MOD- Condenser Fan & Compressor working together by adding a relay

I am also getting lower vent temps at idle and at speed. I recorded the lowest temp with the fan on low, and cruising on the highway at 70:

MBeige · #18 05-11-2014, 02:30 AM

Cool! Nice mod Rich.

Do you have the stock aux fan? Or did you get the larger unit from a V8 W126?

BayouFlyFisher · #19 05-11-2014, 09:48 AM

Which compressor puts less drain on the engine power? Is newer better? Just curious at this point. May get more serious later (too many other real problems to solve first).

Thanks

ROLLGUY · #20 05-11-2014, 10:05 AM

Quote:

Originally Posted by MBeige

Cool! Nice mod Rich.

Do you have the stock aux fan? Or did you get the larger unit from a V8 W126?

Stock fan at 70 MPH down Cajon Pass.

ROLLGUY · #21 05-11-2014, 10:22 AM

Quote:

Originally Posted by BayouFlyFisher

Which compressor puts less drain on the engine power? Is newer better? Just curious at this point. May get more serious later (too many other real problems to solve first).

Thanks

Some would say that they are all equal, and others would say that one takes more power over another. I can only go by my own experience, in that I have not had a working R4 for long enough to tell the difference. I also don't know if anyone has done any kind of "dyno" test on A/C compressors to know how much power they consume. I can say that I believe that the 7 cyl is a tiny bit more efficient than the 5 cyl, but have no comparison of the Sanden with the R4. Practically ALL compressors in use nowadays are of the same or similar design as the Sanden ("wobble plate" axial piston), so yes, the newer design is better. The R4 is a radial 4 piston compressor (thus the R4 designation), and relies solely on lubrication from oil in the refrigerant. A refrigerant leak provides an exit for the oil as well, and leads for an early demise of this type of compressor. The old York and newer Sanden style compressors have an oil sump that provides lubrication for the compressor internals, as well as a small amount of oil in the refrigerant.....Rich

Graham · #22 05-11-2014, 10:50 AM

What sort of pressures do you see when you have those low vent temperatures (assuming R134a)?

Given these cars were designed for lower pressure R12 and the parts are getting old, I would be concerned that given my luck, something else in the system could fail right after I installed the Senden compressor.

(BTW, I have a blown evaporator in my W210 at present. It blew right after I got pressures back up by using a sealant

)

ROLLGUY · #23 05-12-2014, 12:38 AM

Quote:

Originally Posted by Graham

What sort of pressures do you see when you have those low vent temperatures (assuming R134a)?

Given these cars were designed for lower pressure R12 and the parts are getting old, I would be concerned that given my luck, something else in the system could fail right after I installed the Senden compressor.

(BTW, I have a blown evaporator in my W210 at present. It blew right after I got pressures back up by using a sealant

)

I am not sure the exact pressures. My A/C guy does the vac and charging for me (he has done 10+) and he is the expert. I am sure the pressures are within acceptable limits for the current system. Having the fan pushing air through the condenser at the start is sure to lower the temp, and thus lower the pressure in the system.

BillGrissom · #24 05-12-2014, 03:27 PM

Graham, if you were running R-134A with PAG oil, you don't want to leave it long with no charge since PAG oil absorbs moisture from the air and forms corrosive products. Human nature being as it is, many people neglect their AC for a year or more, then when they have it fixed, they blame the new products or labor for causing a failure that they "never had before". Particularly true in newer cars w/ aluminum components (not ours). At a minimum, I suggest flushing out the old oil before letting it sit. One clueless VW owner (other people fix his car), has been flaming Duracool claiming their hydrocarbon refrigerant corroded his condenser. It had been sitting w/ no refrigerant pressure for long time before w/ PAG oil in it.

You can find expected refrigerants pressures in a "saturation chart". The low pressure is a function of the evaporator temperature and the high pressure of the condenser temperature. The later is hotter than the ambient air, especially if idling and with the fan off. Ditto for the interior. I like to see 10-30 psig low side and 90-180 psig high side, when using Duracool (similar pressures as Freon). With R-134A, the high side will run a bit higher. If >250 psig, you run the risk of stalling the compressor, which starts the clutch slipping and soon smokes it, with no warning until you see smoke coming from under the hood. A good reason to never overcharge refrigerant.

Graham · #25 05-12-2014, 07:45 PM

Quote:

Originally Posted by BillGrissom

Graham, if you were running R-134A with PAG oil, you don't want to leave it long with no charge.........

Replacing the evaporator on a W210 is an expensive job. Something like $4500 from dealer using OE parts. One shop quoted me about $2300 but using a cheap import evaporator. Still a lot of money on a car that is worth at most $4000 with a working A/C. So it may never get done! Luckily up here we don't need A/C much. But I get your point.

Quote:

Originally Posted by BillGrissom

You can find expected refrigerants pressures in a "saturation chart".

I think I understand the thermodynamic part Bill. I asked the question because of the very low vent temperatures quoted (which, as it turns out, may not have been accurate). To get those on my W210, pressure would have to be high. Maybe ~18 bar (Climate control display on W210 allows you to read out most A/C data). Knowing the pressure would just have been a double check on the temperatures.

On a W123 that was designed for R12 and is 30 years old, vent temperatures that low and high refrigerant pressures could cause problems. If I ever repaired the A/C on my 300D again, I think I would go to a hydrocarbon refrigerant. The rules up here for even R134a are very strict. We can't buy R134a like you guys can.

Currently we have 4 cars. Only one with working A/C is the 2014 model

ROLLGUY · #26 04-19-2015, 05:29 PM

I am still experiencing low vent temps this season in my 300D. Again, I was traveling the highway (I15 in the high desert) going to Calico Ghost Town, and got real cold all of a sudden. I had my passenger take a photo. I have two gauges, and they agree with one another.....Rich

Caseyc · #27 04-19-2015, 07:36 PM

Rich, that is great news. I'm glad to hear things are still cooling strong. How's the 240D with the 5 cyl Sanden working out? I'm still out of town, but when I get home, I'll be hitting you up for a complete kit. You got any leads on a 7 cyl sanden yet?

Casey

ROLLGUY · #28 04-20-2015, 12:54 AM

Quote:

Originally Posted by Caseyc

Rich, that is great news. I'm glad to hear things are still cooling strong. How's the 240D with the 5 cyl Sanden working out? I'm still out of town, but when I get home, I'll be hitting you up for a complete kit. You got any leads on a 7 cyl sanden yet?

Casey

A friend has the 240D, and as far as I know it still works great. His family took the car on a 500 mile trip a few weeks ago with a cargo bag on top of the car, and four people inside. I was told the car worked flawless and it was hot, so I assume the A/C still worked great.

I have a 7 cyl available now (New Old Stock)....Rich

leathermang · #29 05-08-2015, 09:09 PM

Quote:

Originally Posted by Doktor Bert

I've been running this thing like this for 88,000 miles. I have found that the fin surface temps never get as cold as the air temps, when checked with an infra-red...FWIW

FWIW..... an infrared thermometer has certain rules due to the physics of the situation... it would take a contact thermometer on the fins to determine accurately their temperature..... as you have experienced.
There is no way for the air at the vents to get colder than the fins on the evaporator....
Listen to Vstech ..... an AC professional.....

When someone has done all the normal update stuff to one of these old cars and is not getting the cooling they expect....
it is almost certain that the FINS on the evaporator are clogged..dog and human hair, pollen, etc over the years builds up.... and the fins on the condensor also need to be straight and clean... with a high performance fan running all the time the AC is on.... even more important if using R134a. Just due to its slightly less efficient molecular structure...

sleepstar · #30 05-08-2015, 09:38 PM

how do you get temps that low? on my 300d the ETR switch cuts the compressor absurdly early.. like around 38 degrees. i think this was the factory setting. do you put in a different ETR switch or something?