I have been working on this 1980 300TD for some time, trying to get the climate control to work. I have installed a refurbished servo and amp, acquired from George Murphy. I tested the resistance chain, and found a faulty in-car temp sensor. I am going to order a new one, but in the mean time, will a fault in the resistance chain cause the blower not to come on at all in any mode(other than defrost)? From what I understand, a fault in the chain will only affect the mixture of the air temperature from the vents.

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Andrew Villasenor
805-720-5057
1984 300D turbo 5-speed manual(daily driver)
ALL MY DIESELS RUNNING WVO
Everything is for sale for the right amount
Ebay Store

I am currently in the midst of a similar task, also with a 1980 300td, coincidentally.

You say the in-car sensor is faulty, do you mean it is dead or that it isn't providing the proper signal? My understanding is a loss of input from any sensor in the chain will prevent the system from working.

On the blower: I was recently reminded that apparently, a blower motor with well worn brushes may not come on except on defrost, because only on that setting does it get a full jolt of power (max speed). (I am passing on what was reported to me, I am not the owner of that factoid .)

Have you tried applying 12v directly to your blower?

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

That is my experience. My '79 has a kind of sad, squeaky blower that works OK but sometimes won't start without being hit with a jolt of Defrost first. It matches with what I've read elsewhere.

A 12v hit to the blower is the best way to eliminate it as the problem. While working to get the ACC in my '85 working I put 12v on the blower as one of the first steps. It worked beautifully. I then tested for power at the blower plug and found none. With just those two simple diagnostic steps I was able to determine that my main issue was a lack of power delivery to the blower, somewhere along the chain.

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1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

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Visit the W123 page on iFixit for over 70 helpful DIY guides!

Do you have the manual, very retro 60s vibe going on here, worth reading just for that...

1971 Chrysler Imperial Auto-Temp 2 Service Reference Guide - Session 281

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

did you test the CC vacuum supply (green/yellow)? No or low vac will give you defrost only.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

Thats hard to stop reading, I keep wanting to follow the little man in the suit. Was this the same system as the 1st gen mercedes ACC?

Yes, they borrowed it from Chrysler.

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1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

The Baja Arizona Oil Burners Send a message if you'd like to join the fun
Left to Right - UberWasser, Iridium, Stuttgart-->Seattle,, mannys9130

Visit the W123 page on iFixit for over 70 helpful DIY guides!

Unfortunately, that manual is the only remotely amusing thing about ACC II.

It does make a refreshing change from the standard Mercedes shop manual fare, however. I always feel like I am disassembling an ME 262 when I use one of those.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

If you have a w123 with accII and you are having problems, please check your vacuum lines near the battery. Fixed my problem.

Attached Thumbnails

 

__________________
Andrew Villasenor
805-720-5057
1984 300D turbo 5-speed manual(daily driver)
ALL MY DIESELS RUNNING WVO
Everything is for sale for the right amount
Ebay Store

so, are you good now?

__________________
Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

Before you installed the new amplifier and servo, did you test the aux water pump to see if it is functioning?

If this is froze, it will fry your new amplifier.

If your sensor tube behind the dash has crumbled the system will not be able to tell the cabin temperature.

Under the servo is a thermostat, there is two red lines running to it. The heat will not come on, until that thermostat reads the right temperature to allow the vacuum into the system

The factoid on the blower motor is 100% correct, over the years the brushes will get worn in a scoop type pattern and seen the brushes will barely touch the commuter, if you remove the brushes and file the brushes flat....they will allow fully contact...

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