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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,432 Posts
Discussion Starter #541
Took a trip to Carl Mossers place to test out Samson's AC today. Drive was uneventful both ways but results were 107 dismal. Meaning the AC performed just like a stock 560SL AC system (next to useless). OAT temp was 92°F Duct temps was running 62° F with windows open, ~ 58°F with Windows closed. Duct temp would go down to 48°F with windows closed blower on auto and re-circulation on. But no matter what I did cabin temp could only be brought down to 76°F. Believe it or not that is all withing spec for a 107.

The other thing I needed to check was does the car over heat. It ran significantly hotter as expected, Got up to 100°C on the highway ~ 105°C when I got off the highway and was stopped in line for gas. Hard to tell on a short trip like this but gas mileage came out to 21 MPG.

Carl has some pictures hopefully he will post them here.
 

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1983 380SL, 2000 S430, 1991 420SEL (retired) - RHD
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5,639 Posts
Took a trip to Carl Mossers place to test out Samson's AC today. Drive was uneventful both ways but results were 107 dismal. Meaning the AC performed just like a stock 560SL AC system (next to useless). OAT temp was 92°F Duct temps was running 62° F with windows open, ~ 58°F with Windows closed. Duct temp would go down to 48°F with windows closed blower on auto and re-circulation on. But no matter what I did cabin temp could only be brought down to 76°F. Believe it or not that is all withing spec for a 107.

The other thing I needed to check was does the car over heat. It ran significantly hotter as expected, Got up to 100°C on the highway ~ 105°C when I got off the highway and was stopped in line for gas. Hard to tell on a short trip like this but gas mileage came out to 21 MPG.

Carl has some pictures hopefully he will post them here.
There's nothing but heat surrounding the plastic heater box on 107's - no insulation at all. Maybe some insulation pads around the box might help . Maybe in the blower motor box as well ?
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,432 Posts
Discussion Starter #543
There's nothing but heat surrounding the plastic heater box on 107's - no insulation at all. Maybe some insulation pads around the box might help . Maybe in the blower motor box as well ?
Sounds like a good idea. But I'm not going to remove that just yet. For the moment I'm going to focus on the expansion valve. My low side pressures are too low like 16 PSI. I hound a German made expansion valve in the UK so I just sent a request to see if they will ship it to the states. The one that's in there now is URO.
 

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1983 380SL, 2000 S430, 1991 420SEL (retired) - RHD
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5,639 Posts
Sounds like a good idea. But I'm not going to remove that just yet. For the moment I'm going to focus on the expansion valve. My low side pressures are too low like 16 PSI. I hound a German made expansion valve in the UK so I just sent a request to see if they will ship it to the states. The one that's in there now is URO.
I was thinking of applying in situ by coming in from the sides rather than removing the box which is a major PITA.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,432 Posts
Discussion Starter #547
I was thinking of applying in situ by coming in from the sides rather than removing the box which is a major PITA.
The blower area being next to the fire wall might be a goo area to insulate. The plastic cover should be real easy.
 

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1983 380SL, ivory/dk brown, 46k miles, dual roller timing chain. 1986 560SL, red/white, 190K mile.
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6,954 Posts
John Roncallo came by for a visit. This was part of his test drive to test out his Air Conditioning
he had to fabricate for his V12 engine powered car he calls Samson.
It was a hot high humidity day. I took the opportunity to pick this experts brain about
some idling OCDs I had with my 560SL. Nice to have someone to sit around and
drink some beers even if it was Covid-19. We were in the garage with the fan blowing as long as we could
stand the heat until we found a cool place to just sit and talk. I think if I had recorded our
conversation about R107s folks here would find it interesting. No politics, mostly
about Johns work on his V12 Samson R107, some remembrances about some past BenzWorld
postings, remembering some other folks we met on this forum, and how hard it is for old farts like
us to get access to controls and AC parts behind the dash, how much we would pay for a
560SL parts car, and what the next 10 years will be like.
John's a nice guy and has a lot of hands on experience with our R107s.

Selection_784.png
Selection_783.png
Selection_785.png
 

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1973 450 SL
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2,062 Posts
What ambient temp and pressures were you reading. I am fast coming to the conclusion my TXV is clogged.
roncallo,

That vent temp picture was taken on July 5th last summer after installing a new temperature vacuum switch and tweaking my pressures. It is the coldest I've ever recorded with that little gauge. I normally see 38 - 40F coming out of the vents when I crank it full cold. I don't know the ambient temp but it is hot here in July. Here is what my system pressures were (taken 30 June 2019).

185 over 42

2636486
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,432 Posts
Discussion Starter #550
Envirosafe

The End
It's good to see that you can get down to 30°. But your compressor should be cycling off before you get that low, typically cycling off at 36° to 40° after 3 cycles of the clutch and it should cycle back on about 8° higher. You might get away with that in Albuquerque because it so dry, but here in NC it would freeze up the evaporator. It looks like you need a new or adjusted evaporator temperature switch. Your early 107 should have an adjustable switch 1 turn = ~3.6°. Most 107's should get to this level on the low blower setting with windows closed. I was getting there when I first charged my system but now I'm not. That's why I believe my expansion valve has failed.

There real performance test needs to be performed with the car in the shade, blower on high speed, engine at 2000RPM and windows open. Under those conditions, unless its cold out the compressor shouldn't cycle and I will bet a bear you wont get 30° in Albuquerque this time of year.
 

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1983 380SL, ivory/dk brown, 46k miles, dual roller timing chain. 1986 560SL, red/white, 190K mile.
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6,954 Posts
I will say the AC is considerably cooler in my 1983 380SL versus my 1986 560SL.
My 380SL does have a replacement newer more modern AC Compressor - AC Delco 15-22255
aluminum body unit, and a new Receiver/Dryer.
The original A6 compressor was leaking at the rear - that leak was hard to find and it went undetected
over the years by several AC shops until I took the time to mess with the AC and use Envirosafe's
pine scented dye that did not require a UV light to detect.

My 560SL has the original (non-AC Delco) compressor and I did not replace the Receiver/Dryer.
Both were vacuumed and both got 2 cans of Envirosafe Freon.
After meeting with John Roncallo yesterday, he mentioned that the hoses for the AC gauges could hold
as much as 2oz of Freon. I'm going to go back and see if perhaps my 560SL is undercharged or perhaps both.

Pressures temperatures are different between the two SLs.

1983 380SL:
Selection_789.png


1986 560SL:
Selection_788.png
 

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1973 450 SL
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2,062 Posts
Totally agree - that picture concerned me too for possible freezing. I have not seen that temp since; my AC system was just showing off after getting some TLC. I'm not touching that system for now. When I dial it full cold, 38 - 40F (at the bottom edge of that green band) is perfect.

As for the compressor cycling, that happens as it should. I can feel it via engine load and see it via electrical load. The earliest version of these AC systems had a light in the temperature vacuum switch that illuminated only when the compressor was engaged. MB changed that to normal 58 (maybe 58d) power before 1973. My guess is customers found it distracting. There is a note in the service manual about the change. Early cars have an open 2-pole female connector behind the AC panel as a consequence.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,432 Posts
Discussion Starter #553
roncallo,

That vent temp picture was taken on July 5th last summer after installing a new temperature vacuum switch and tweaking my pressures. It is the coldest I've ever recorded with that little gauge. I normally see 38 - 40F coming out of the vents when I crank it full cold. I don't know the ambient temp but it is hot here in July. Here is what my system pressures were (taken 30 June 2019).

185 over 42

View attachment 2636486
Not sure about Envirosafe but that looks perfect for R134a. I envy you low side, I'm only getting 16. Did you measure that with the windows open at 2000RPM. Your high side actually looks low for a hot day in Albuquerque, do you have some extra electric fans installed.
 

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1973 450 SL
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2,062 Posts
Not sure about Envirosafe but that looks perfect for R134a. I envy you low side, I'm only getting 16. Did you measure that with the windows open at 2000RPM. Your high side actually looks low for a hot day in Albuquerque, do you have some extra electric fans installed.
The only thing I know about automotive AC came from several phone conversations with an old timer tech at Envirosafe. He had the same comment about my high side but sort of blew it off when I told him my results and the fact that the compressor was behaving well.

Windows were open, I did not have a helper because SWMBO was running errands. Best I could do was rev the engine for a minute (tech told me to) then get out and quickly record the pressures.

I have the early 9" factory installed noise maker that MB jokingly called an aux fan. The only modification I've done to that is build up a circuit to make it run on circuit 30 power for 2 conditions after I shut the engine off - irrelevant to this discussion.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
Joined
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10,432 Posts
Discussion Starter #555
I will say the AC is considerably cooler in my 1983 380SL versus my 1986 560SL.
My 380SL does have a replacement newer more modern AC Compressor - AC Delco 15-22255
aluminum body unit, and a new Receiver/Dryer.
The original A6 compressor was leaking at the rear - that leak was hard to find and it went undetected
over the years by several AC shops until I took the time to mess with the AC and use Envirosafe's
pine scented dye that did not require a UV light to detect.

My 560SL has the original (non-AC Delco) compressor and I did not replace the Receiver/Dryer.
Both were vacuumed and both got 2 cans of Envirosafe Freon.
After meeting with John Roncallo yesterday, he mentioned that the hoses for the AC gauges could hold
as much as 2oz of Freon. I'm going to go back and see if perhaps my 560SL is undercharged or perhaps both.

Pressures temperatures are different between the two SLs.
The Delco A6 compressor was the best compressor in the world, not sure about the replacement.

The stock 560SL requires 3 12oz cans of R12 or about 2.5 cans of R134a, not sure about Envirosafe.

That 2oz in the hose comes from the MAC 609 certification study guide. Be careful they stated that the SAE measured as much as 2oz and gave no conditions for the testing. One of the things I do with my 134a gauge set is leave the Freon in the gauges so the next time I charge its accounted for. I cant do that with the R12 gauges because they don't have the same self sealing quick disconnects. Also I disconnect the low side immediately after shutting off the engine so that it is at its lowest pressure and I wait a few minutes to disconnect the high side. I attached a link to the 609 test sight. It has the study guide that can be down loaded for free. Its about 50 pages and well worth the read. You can also take the test for $20. Taking the test gives you the ability to legally purchase R12 in any amount or R134a in 30# cylinders, usually required to purchase on E-bay.

 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
Joined
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10,432 Posts
Discussion Starter #556
The only thing I know about automotive AC came from several phone conversations with an old timer tech at Envirosafe. He had the same comment about my high side but sort of blew it off when I told him my results and the fact that the compressor was behaving well.

Windows were open, I did not have a helper because SWMBO was running errands. Best I could do was rev the engine for a minute (tech told me to) then get out and quickly record the pressures.

I have the early 9" factory installed noise maker that MB jokingly called an aux fan. The only modification I've done to that is build up a circuit to make it run on circuit 30 power for 2 conditions after I shut the engine off - irrelevant to this discussion.
Sounds good. I have been setting my gauges up on a camera tripod so I can see them as I run the engine. I didn't realize the aux fan was that small on the early 107's
 

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Premium Member
1983 380 SL
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3,032 Posts
So now I'm at a total stand still. Second refrigerant recovery tank I ordered has not shipped yet. The new 3 qt windshield washer tank is on back order until late July. In any case I cut the bottom off my 4 qt tank to bring the size of the tank equal to a 3qt tank. With that I can complete the mounting brackets and the rest of the installation hardware. I got the mounting and routing of everything all figured out.

The reservoir was fit into my test vehicle (Ebola) and moved around in different positions until a result that worked was found. Note the target practice holes drilled on Ebola to find the best installation location. The circled holes are the one I will actually be using. Once a successful solution was available and tested on the real car (Samson), a drill guide was fabricated so that hole locations could be transferred back to another 107. The drill guide was made by bolting pieces of sheet metal to preexisting holes in the 107 chassis. Since the new mounting holes were already established in the vehicle, new matched drilled holes needed to be drilled into the guide sheet metal that matched up with the existing holes already drilled into the chassis. This is done with the tools shown in the third and fourth pictures. I don't know what they are called but they are used in the aircraft industry to replace panels on aircraft that have preexisting holes underneath.

I needed to do this on both Ebola and Samson because without fenders on Ebola the final fit checks could not be established. With the reservoir mounting established, everything else can now be demonstrated on Ebola. With the final mounting position established on Ebola, I was now able to locate a suitable pass through position and hole saw it out and install a chaffing strip as shown in the 5th picture.

Final mock up of the tube is shown in picture #6 and 7. The sticking into the engine compartment will be turned up and welded to a cap shown in picture #8.

Note that this is a mock up filler tube. The actual filler tube will be fabricated from a 60° mandrel bend for the bend turning into the engine compartment and a 90° mandrel bend to turn the tube up once it penetrates the engine compartment. Those bend should be on order and I will be able to complete those prior to the replacement 3qt reservoir showing up.

I will also be getting a professional welder to do all the real welding. Hopefully he will do pornographic welding.
You lost me on pornographic welding.
 
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