AC Help !! convert back to R12 - Page 4 - PeachParts Mercedes-Benz Forum

WDBCB20 · #46 05-14-2020, 11:26 AM

Quite the pristine specimen!

Diseasel300 · #47 05-14-2020, 11:31 AM

Quote:

Originally Posted by WDBCB20

Lol. To be fair my '83SD did see 34°F (even below) at the vent at minimum of 45mph with outside temps of high 80's low 90's and typical FL humidity running Duracool (hydrocarbon) refrigerant. Of course in traffic/idling, as you note, it would go up to 50°F and more.

Have a can of grinding rocks R4 in my new '85SD giving at best 55°F at highway speeds so it's due for a refurb. Hence my previous question.

The Gen I cars have a mechanical evaporator thermostat to trip the compressor to keep it from freezing the evaporator. They are supposed to trip right around freezing, but there's some tolerance and it's not uncommon to see vent temps in the low-mid 30s on them. The Gen II cars have a thermistor sensor that communicates with the pushbutton unit to trip the compressor at 3-5˚C (38-41˚F) so the lowest realistic vent temps you will ever see on a Gen II car is 42-43˚F under ideal circumstances regardless of what refrigerant is being run.

I've been thoroughly disappointed with hydrocarbon refrigerants. When the engine RPM is up and the car is moving, they cool like crazy! Painfully cold! Then you come to a stop light...... 65-70F vent temps are simply not an option for me, sorry. R134a seems to keep the Gen II cars at <55F at idle with the fan on high. Once the cabin has pulled down, it'll significantly longer to creep up into the 50s. Soon as you start moving, down it goes again.

WDBCB20 · #48 05-14-2020, 11:54 AM

Quote:

Originally Posted by Diseasel300

I've been thoroughly disappointed with hydrocarbon refrigerants. When the engine RPM is up and the car is moving, they cool like crazy! Painfully cold! Then you come to a stop light...... 65-70F vent temps are simply not an option for me, sorry.

Yes, I imagine the Texas environment is even more demanding of the AC.

Have contemplated doing a hack grafting the innards of cooled seats off a Saab/Lexus/Caddy into the MB seats and tapping a duct into the rear AC conduit...

Diseasel300 · #49 05-14-2020, 12:16 PM

Quote:

Originally Posted by WDBCB20

Yes, I imagine the Texas environment is even more demanding of the AC.

The heat-gain in this area during the summer is crazy. We routinely get into the triple digits with variable humidity levels and lots of sunshine. The hardest the A/C has to work is when it's over 100 and the humidity is low, vent temps matter! Ceramic window tint helps a LOT, but I haven't yet done it to my 350SD. Despite that, it still has one of the best A/Cs of any car I have access to.

Fred Jan · #50 05-14-2020, 01:45 PM

Quote:

Originally Posted by Diseasel300

The heat-gain in this area during the summer is crazy. We routinely get into the triple digits with variable humidity levels and lots of sunshine. The hardest the A/C has to work is when it's over 100 and the humidity is low, vent temps matter! Ceramic window tint helps a LOT, but I haven't yet done it to my 350SD. Despite that, it still has one of the best A/Cs of any car I have access to.

I would be more than happy if you recommend a flushing agent, I spent the last 2 hours searching for one and checking the review, everything says "the solvent is super oily" "did not evaporate" "leaving a film behind" "leaving residue" :-( , Jesus !! I din't know its that hard to find a good product

Diseasel300 · #51 05-14-2020, 01:53 PM

Quote:

Originally Posted by Fred Jan

I would be more than happy if you recommend a flushing agent, I spent the last 2 hours searching for one and checking the review, everything says "the solvent is super oily" "did not evaporate" "leaving a film behind" "leaving residue" :-( , Jesus !! I din't know its that hard to find a good product

I've used Acetone several times in the past, most recently on a BMW E23 in March. Keep it off paint or plastic (it will eat both). Evaporates almost instantly and it's ~$13 for a gallon at Home Depot.

Fred Jan · #52 05-14-2020, 02:08 PM

Quote:

Originally Posted by Diseasel300

I've used Acetone several times in the past, most recently on a BMW E23 in March. Keep it off paint or plastic (it will eat both). Evaporates almost instantly and it's ~$13 for a gallon at Home Depot.

You are the man !! can i use 80% alcohol :-) i have a lot

Fred Jan · #53 05-14-2020, 02:10 PM

Quote:

Originally Posted by Diseasel300

I've used Acetone several times in the past, most recently on a BMW E23 in March. Keep it off paint or plastic (it will eat both). Evaporates almost instantly and it's ~$13 for a gallon at Home Depot.

By the way is the suction hose (the one with the muffler or filter in it) is this flush-able?

Diseasel300 · #54 05-14-2020, 02:22 PM

Quote:

Originally Posted by Fred Jan

You are the man !! can i use 80% alcohol :-) i have a lot

No. It has water in it (20%). You'll spend the rest of your life trying to dry the system out. Acetone sold at the hardware store is 100% strength and will basically flash-dry.

Quote:

Originally Posted by Fred Jan

By the way is the suction hose (the one with the muffler or filter in it) is this flush-able?

The updated hoses have a large bulge to act as a sort of accumulator on the suction line. It is just a wide spot in the hose, you can flush it. The filter/drier on the high side should be discarded and replaced with a new one. It should be the very last thing installed in the system and a vacuum pulled immediately after connecting it and tightening everything down.

Fred Jan · #55 05-15-2020, 09:53 AM

Thank you for the valuable information !!! I am waiting on my seals, expansion valve, the Nylog blue, dryer to start working on the AC. I will keep you updated.

Diseasel300 · #56 05-15-2020, 09:57 AM

Good luck! Cold A/C is a wonderful thing. When properly charged and functioning, these Gen II 126's have a good A/C system.

Fred Jan · #57 05-15-2020, 11:20 AM

I charged my Uncle 2001 buick century this year after a long time of sitting, replaced a couple of leaky hoses, I hope I will get one of these lol

https://ibb.co/y4wMYZm

Diseasel300 · #58 05-15-2020, 12:22 PM

Might wanna check the evaporator switch or sensor on that Buick. The coil should never be allowed to reach freezing or below, you'll grow frost in humid weather eventually freezing the coil.

JHZR2 · #59 05-15-2020, 12:59 PM

Quote:

Originally Posted by Fred Jan

The car had been charged 4 time in the past 3 years:

Dealer ship result:55F from center vents at night , mid 70 during the day
AC shop result: 52 from center vents at night , 70 in during the day
Me result: 52 from center vents at night , 70 in during the day
Me Using enviro safe 134A replacement, same result

engine temp above +80, when driving 80, sitting in traffic its better to roll down the windows and 100c engine temp

So now youre using ES-12a?

Regular or industrial? Did you pull a vacuum?

Max pressures can go haywire with these blends depending upon how they are charged. That can affect efficacy.

Fred Jan · #60 05-15-2020, 11:27 PM

That Buick century has only 30K miles in it, he drove it only to church one a week, :-) I was impressed with the AC, really cold you can't sit on the leather seats

Quote:

Originally Posted by Diseasel300

Might wanna check the evaporator switch or sensor on that Buick. The coil should never be allowed to reach freezing or below, you'll grow frost in humid weather eventually freezing the coil.