If I bypass the servo, can I get heat to my feet or just defrost?

I have all the major parts for this, but want to know if there is something I can/have to do in order to get heat at my feet.

Thanks!

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Ginny in Denver-ish
78 300SD, 265K (mine)

As long as the electric and vacuum portions of the servo are operating and you only bypass the coolant from the bottom section of the servo, I think all the rest of the servo functions should work. This would occur in situations where the only problem with the servo was a leaking bottom section which holds the coolant and coolant control valve.

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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

If you mean that you are bypassing the servo altogether, because it is a demonic piece of crap that besmirches the fine reputation of our otherwise perfect cars, then I think the only way you can redirect the heat is to mess with the vents.

The default for everything is defrost, fortunately. To alter this, I think you need to get into the dash, not sure where, and manually open and wedge or tape flaps into different positions. It would be a semi-permanent thing, not controllable from the switches, which are dead anyway if you have thrown away the piece of junk servo.

I too am considering this change, if I can get my blower working again. I'd be interested in whether anyone here has wedged their vents and how they did it.

Good luck.

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Where there's a will there's a way
1978 300D

Provided you don't have a vacuum leak(s), you can study the diagrams, connect the vacuum hoses you need at the servo valve, and energize the correct solenoid behind the dash to open whatever valves you want...

I'm simply too tired to look at it, so your on your own on this one...

ps: been doing this type of work on a R107 for a while to help a friend in need, so "sick and tired" is more likely a better euphemism...

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RM Smith
1988 560SL

"Where is it again that we are going, and why are we in this handbasket"?

Before I cut into the whole shebang, I was thinking I might try an amplifier replacement first. Does anyone know a friend of a friend or anyone who might have a known working amp they would sell me?
The amp was making clicking noises on and off before the heat stopped working. Could be the amp. . .

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Ginny in Denver-ish
78 300SD, 265K (mine)

What are your symptoms and is the servo leaking? The servo might be fine. For instance, there is a main vacuum control switch behind the glove compartment and if that switch is not getting vacuum or is broken, the whole system won't work.

__________________
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

so glad to hear there is a way to bypass the servo --- mine is shot...and the Minnesota winter is looming...could anyone please explain to me how I could just get defrost? All I care about is keeping the windshield clear of ice, etc...and just a little extra added heat to keep fingers somewhat warm...

My defrost WAS working darn good --- then while driving it shut down. Then I put in a new fuse and it works for a little while, then it blows again.

So, time to get into bypassing it since I am in no position to upgrade this servo to the $700 one....yet..

thanks

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1979 300TD - 700k+ (looking for a fold down 3rd seat)
2000 VW Eurovan MV - 140k

The heat does not work, but all settings blow fine. The whole system works fine, just doesn't blow heat. When I didn't have heat before, the amp got replaced and I had heat. After a couple years, the amp started making clicking noises. Sometimes the clocking would lead to no heat for a while, then sometimes it would get clicky again and I'd have heat. The sound was definitely coming from behind the glove box, so I am only presuming that it was the amp.

I don't want to cut into the system if I don't have to. What does this sound like?
Thanks!

__________________
Ginny in Denver-ish
78 300SD, 265K (mine)

I'd try another amp. I had a spare until I sold my 116 but it went with it. But as long as the rest of the system works and it blows I would think bypassing the coolant lines from the servo should get you heat.

__________________
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

Can I rebuild mine?
What does that take? I haven't taken apart my old one but what does it mean to rebuild an amp?

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Ginny in Denver-ish
78 300SD, 265K (mine)

No easy answer... Here's some of my saga:

http://www.peachparts.com/shopforum/diesel-discussion/304961-its-heater-season-acc-fun.html

I finally got mine working well but it took a lot of work and some $$. I believe if your amps are crapping out the problem is most likely the servo. Probably the water valve portion unless the gear train/servo motor part got wet and corroded.

You won't get any feet heat with the 116. Heat is routed to the outside vents and the door panels when max heat is on.

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

Do you have a fuse on the auxilliary pump? A seized unfused auxilliary pump is known to take out the amps.

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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

...and a seized servo can also take out an amp...

__________________
RM Smith
1988 560SL

"Where is it again that we are going, and why are we in this handbasket"?

This sounds like the clicking behind the glovebox:




The white and yellow "pods" switch the ACC system and the auxiliary pump. I believe the white one is the "master" ACC vacuum switch and the yellow is for the aux. pump. They do click when vacuum comes up and the system switches on. It seems like a vacuum leak could cause either switch to turn off/on.

The aux. pump will be on any time the temp is below 79 F and the ACC system is turned on.

Do you have a mity-vac type pump?

The amp is all solid state and doesn't have any clicky things. It's kind of like a transistor radio. You'll find it screwed to the metal (left center) plate in the picture. It has little square waffle looking holes in it and a plug with a bunch of wires.

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

Thanks, I did already take out the amp. I replaced it with another but didn't know if it worked or not. Seems it didn't.

__________________
Ginny in Denver-ish
78 300SD, 265K (mine)