I disconnected all of the vacuum lines on my 1981 240d except the one to the shutoff for the ignition as I have some leaks in the locking circuit. I did this a few months ago while it was hot so I hadn't used the heater or defroster at all, and now my blower motor doesn't come on at all. I checked the fuse and it is fine. Does the system need some sort of vacuum to activate the blower motor? I guess it is possible that the blower motor went tits up, but it worked fine last spring. Any suggestions?

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1984 300TD 1981 240D

I doubt it needs vacuum. The manual climate control on my 409d didn't. Just look at the main vacuum line. Is there any line coming off it other than the shut off and the doors? A climate control line would be green.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

No it's all cable operated vents and electric blower motor. But like kerry said if you do have some climate control vac you will have a green vac lines coming off the main vac line in the engine bay.

Did you pull the fuse or just look at it? I've seen these fuse get little circles cut out of them from the clips that hold them. The clip slowly cuts a little hole in the end of the fuse, and leaves poor contact. So make sure you pull it out and inspect it if you haven't. If you do find this situation, make sure to find the cut out bit. You don't want it floating around in the fuse box.

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There is a green vacuum line at the firewall that I disconnected. I assumed it was for the climate control to switch between the various vents. I hooked the vacuum tester to it and it does not hold vacuum so I left it unhooked. Would that keep the blower from coming on? PS- I checked the fuse with an ohmmeter after replacing it just in case that was the problem. According to my FSM I have the 3rd version of manual climate control.

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1984 300TD 1981 240D

The later vintage of "manual" used a vacuum switch with a defrost position rather
than cables to operate the air doors.

Its more likely that you have a burned out speed resistor network.
which is mounted in the left defroster vent on some 240D models, on the fender well
in others. I'm note sure where the MY break is, since I've seen 1979/80 models with
either mount type. It probably depends on airbox vendor, Siemens or Behr.

Or a bad switch, if you've hot wired the blower and know it works.
You can jumper the four pin connector at the blower cable to jumper
out the lower speeds and get a single high speed blower.

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--frankb

1982 300TD 617.912 <NLA> . 1975 2002 E10-EFI . 1976 914c6 . 1983 MG LMIII <NLA>. 1988 Montero / 616<NLA> . 2001 TLS . 2005 Saab 9-5 Wagon

A 409d????

I have never heard of one. What is it exactly??? Are you referring to a T1????

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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

Thats my next step to start fooling with. I just want to make sure that vacuum isn't the problem before I start chasing my tail as it worked before I disconnected the vacuum, albeit many months before.

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1984 300TD 1981 240D

Pretty sure, although I can't find the high resolution side shot to read the badge.

__________________
--frankb

1982 300TD 617.912 <NLA> . 1975 2002 E10-EFI . 1976 914c6 . 1983 MG LMIII <NLA>. 1988 Montero / 616<NLA> . 2001 TLS . 2005 Saab 9-5 Wagon

Yes, 409d is a van with a 617 engine. Doesn't look like the van pictured above though. It's the T1 body style (I think that's the correct designation). The van pictured above is the larger van versions.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Later 240Ds have one vac pod, it is actuated by the detent on the a/c temperature wheel.

There is a vacuum solenoid on the far right side under the dash, it uses the green hose from the engine bay to shut the recirculating damper.

__________________
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

It looks like I have low speed on the blower, but no high speed. I was trying it with the engine on and I couldn't hear the blower! So what could cause no high speed? The switch?

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1984 300TD 1981 240D

Low speed but no high speed is bad switch or bad connection at the resistor.

240D blower control is very simple.

The battery voltage goes to the resistor. The resistor is in two sections. The other end connects to the motor.

The switch connects a couple contacts across the resistor, these short out one part of the resistor for medium or both parts for high. On low the entire resistor is in the circuit.

__________________
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

Good stuff- thanks! I'm gonna open it up today and check it out.

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1984 300TD 1981 240D

Just took the blower out (which was a piece of cake!) and I can't locate the resistor(s)? My FSM shows them in the blower housing under the cover that the plug goes into, but it looks like a straight connection to me. It is a Siemens blower.

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1984 300TD 1981 240D

Have you looked in these locations?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13