adding a second evaporator? - PeachParts Mercedes-Benz Forum

ngarover · #1 07-29-2011, 10:06 AM

on my 85 300cd

I have an extra evaporator sitting here from a 92 Bonniville SSEi. Would it make any difference in cooling if I had it put in the system? I've been chasing A/C issues all summer.

No idea when the system had been last ran when I got the car, but have a feeling it had been 7-8 years. The system had bee converted by MB some years ago to the newer gas.

Charged system and pressure held but belt was shot. replaced belt and system would come up to pressure, worked for a bit then started to make noise and clutch would shut off/not engage sometimes.

Got the system to work for the day, went to pick up my kids and left the car idle after climbing lookout mountain here in GA, it was HOT out... over 100F. Temp gauge was hot, but not in red. 12 minutes of idling and I look at the car to see steam Pouring out of the hood! ran to the car and shut it down, turns out the HI/LOW switch burst, releasing all my gas and covering the whole engine with that green dye...

Grabbed the switch from my 81 and swapped them. (The 81's system is down anyways because of a leaking pressure valve) System again worked for about 5 hours. Then the clutch issues started again.

found the Kilma, opened it and found a burned connection, repaired it. system ran for about 30 seconds and snapped the new belt.

Turns out the alinement was off on the pulley. PO seems to have put the washer on the bottom mounting bolt in the wrong place. (I don't know how I missed this the first time, but was replacing all the belts and it was late). Got new belt on, pulley alined and system works... blows week.

Manually opened the center vents, capped the vac to the center pod. replaced the sensor tube with some foam water line insulation.

Swapped in another blower that I know is good, no difference, swapped the A/C controls... no difference. (blower never seems to goto high speed) I know for a fact it works fine when it's in my 81...

I have a feeling the evaporator is plugged up. Going to run to home depot today and get some of that foaming evap cleaner and drop the blower again and fill the box with it, see if I can get it cleaner.

In doing all this, I started looking at that extra evap I have sitting here. It's small, and would fit in the car, should be able to find a nice location for it under the hood, but would it actually make any difference?

1980sd · #2 07-29-2011, 10:26 AM

I've been tinkering with my AC a bit although I'm no expert...

I would check to see what type of compressor and condenser was used in the Pontiac. Maybe look at CID/revolution of the Pontiac compressor. I'd also check to see if the Pontiac used a parallel flow condenser. And if the Pontiac uses an expansion valve or orifice tube system.

From my limited knowledge I'd say you're on the right track although I don't understand what you mean by "a good location under the hood". In my 116 the evaporator is buried pretty deeply in the dash.

You're gonna have to make some new hoses to plumb the new evaporator in.

junqueyardjim · #3 07-29-2011, 11:53 AM

Man I would forget about A/C in that old car. I know it is hot in Georgia, so just stop for ice cream whenever. If not ice cream, water melon! It is a lot cheaper then trying to fix an old worn out A/C system

1980sd · #4 07-29-2011, 11:05 PM

Quote:

Originally Posted by junqueyardjim

If not ice cream, water melon! It is a lot cheaper then trying to fix an old worn out A/C system

This is wisdom...

vstech · #5 07-29-2011, 11:35 PM

if you are thinking of adding an additional evaporator to increase the cooling in the system, you are going to add HEAT to the already overloaded cooling system... not good. if you want additional cooling the best option is to flush the system, fix all leaks, replace the compressor, and install fresh mineral oil, and convert back to R12

JHZR2 · #6 07-29-2011, 11:46 PM

+1 to VS. Granted a bit more working fluid might be able to hold a bit more heat, and a bigger condensor able to shed more... But putting two in series in the same gas path may just transfer enthalpy thus minimizing the effects.

ds190 · #7 07-30-2011, 12:16 PM

Quote:

Originally Posted by ngarover

In doing all this, I started looking at that extra evap I have sitting here. It's small, and would fit in the car, should be able to find a nice location for it under the hood, but would it actually make any difference?

So you plan on cooling the air under the hood and hope it somehow gets into the interior???

"Evaporator" and "condensor" are not the same thing, right?

ngarover · #8 07-30-2011, 06:35 PM

Quote:

Originally Posted by vstech

if you are thinking of adding an additional evaporator to increase the cooling in the system, you are going to add HEAT to the already overloaded cooling system... not good. if you want additional cooling the best option is to flush the system, fix all leaks, replace the compressor, and install fresh mineral oil, and convert back to R12

WEll, this is the plan then. I got the system to work again for about 12 hours. Cleaning out the evap with that foaming stuff helped the air flow a little. But the system died again... in checking it actually melted the plastic connector for power on the compressor. I'm going to call that compressor dead. I was tempted to grab the one off my 81 and toss it on, but that car is being sold, so once the sales done I get a the new stuff and get this system right.

I can use freeze 12 right?

leathermang · #9 07-30-2011, 06:51 PM

Freeze 12....NOT a good option.
You are not answering our questions... how do you think we can help you ?

It sounds like you either do not know where the evaporator is supposed to be... or you are using the wrong word for the condensor...

You need to read the sticky at the top of the page...