Thanks to JimmyL, my SDL is now full of R12. It now gets 48-50F out of the vents... before was low 60s!

A warning to the wise... be 100% certain that area under the master cylinder is clear of twigs/leaves. That fan resistor becomes HOT. We had a nice little bonfire start up, too bad we forgot the marshmallows

Anyway, to the questions!

Does anyone know how to test the evap temp sender? My compressor runs for quite a while, then just blips off for a while... then back on. So the vent temps do not get really low. Considering every other component is like new, this very easily could be my issue.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

He isn't kidding about smoke from the resistor, and the leaves that provided kindling. Wow!
Yea we couldn't get down much below 48 because his compressor just wouldn't keep running. We had the pressure switch jumpered just to check. And I guess it could also be the CCU.
Dang W126's!!! I couldn't find that evap temp probe anywhere. And that is the first time I saw the famous W126 expansion valve location. Good Lord!! Anyway, can that evap temp probe be jumpered to see if that is the Hitman's problem?
Also a thank you to the Hitman for the 5oz R12 drink we gave the Squash. I never put in the whole amount when I charged him up. Just couldn't bring myself to open up a new can of R12 just for 5 oz's. Just couldn't do it......

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

I don't know how to test the evaporator temp sensor directly but you can take a voltmeter to the low pressure switch to see if you're getting voltage from the PBU when the compressor cuts out.

The low pressure switch is a more common failure point than the evaporator temp sensor from what I've read here.

Sixto
87 300D

Meaning it could be a PBU issue? Or pressure switch? We had the switch jumped.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Anyone want to venture a guess what the difference between compressors on a 1985 300D and a 1986 300SDL are??? My 85 300D produces 42-44 F out of the vents at 60mph and my last 300SDL got quite cold but don't know the temp......all on R135a. If I fine the sensor before you, I'll let you know.

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daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

126 evaporator temp sensor is by the accelerator pedal.

I missed the part about the pressure sensor being jumped. I'd still like to know if there is voltage at the sensor when the compressor cuts out to determine whether the problem is upstream or downstream of the Klima. Or is that jumped as well with an ice cube relay?

Sixto
87 300D

Klima is basically new, maybe 18 months.

I'll check to see if there is voltage there.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

I swapped in a 100% good PBU, Programma reman. Dropped to around 52-54°F at the vents (low speed fan) but still kicks off. High speed was 60-58°F.

I have around a 30-35°F drop from ambient to cabin temperatures, does this seem right? I'm thinking so since the evap core is full of 20+ years of junk.

Now if I still have power to that pressure switch when compressor kicks off, what should I diagnose? What about if there is no power there?

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

System running (PBU on, compressor on) I have no power to the switch when hooked up. It's around 90°F today. Let run for quite a while and raced the idle a bunch, system stayed on.

PBU on, system off (disconnected from pressure switch) I have 12V at the plug.

Hope that's what's needed.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Apparently, the manufacturing tolerances of the evap temp sensor leave quite a bit to be desired. The wide range of acceptability probably has the sensor shutting the compressor down at close to a 42F. temperature in some conditions.

Dave did a bit of research on this and was able to lower the temperature where the switch opened by several degrees by splicing a resistor into the line to the sensor. Do a search on it...........I'm sure it's in the archives.

I'd like to to the same thing on these...........the vent temps are not all that cold and the compressor is not running at 100% duty cycle..........so, an adjustment is definitely necessary for better performance.