I found this tech article and discovered that the foam hose connected to my ACC temp sensor behind the dash is totally shot:

http://www.mbca.org/pages/tech/MBCA_acc_system.htm

The article says to replace the stock foam hose with foam pipe insulation from the hardware store. But do I have to use foam at all? Why foam? Why can't I just use a piece of rubber heater hose, for example?

__________________
'81 300TD turbo <<sold 12/05 to another diesel nut

You want some insulation so the sensor is reading cabin air temperature, not under-dash temperature.

__________________
Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

I replaced mine with foam...its really easy and cheap so you might as well do it the way they designed it.

But, I don't understand the insulation arguement, since the sensor is mounted just under the dash and by the time the air passes through the foam tube, it's already been tested.

Can someone enlighten me?

__________________
1983 300td 240k (down with bad tranny)
1984 300d 222k (daily driver) "Olive"
1997 GMC K2500 105k (sled dog limo)

"The scenery in ANWR is as spectacular as the Grand Canyon and the wildlife is more impressive."

good point.
i'm not sure why you could not use heater hose but all i know is the foam pipe insulation 1) works & 2) is really cheap. so for most diy folks it is a really easy fix to get the CC working again as accurately as this system of temp control is able to.

__________________
1984 300D Turbo - 231k....totalled 11/30/07 RIP

Well, it's not cheap for me. I happen to have a whole bunch of heater hose laying around, but no pipe insulation. So I'll be the guinea pig and try the heater hose and let you all know how it works.

One thing that comes to mind is the stock foam piece can't be airtight, and there must be a reason for that. I just don't understand why they would use 6 inches of foam tube in that one location, while all the rest is solid plastic and exposed to just as much dash heat.

__________________
'81 300TD turbo <<sold 12/05 to another diesel nut

It's been suggested by some, that the foam is NOT for temperature insulation, but, rather sound insulation from the little aspirator motor. Don't know if it's true, just that it's been said. FWIW

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

if you have suitable hose already then sure enough why not try it. failing that, you can buy enough pipe insulation for about 10 300d's at home depot for abt $1.

__________________
1984 300D Turbo - 231k....totalled 11/30/07 RIP

Oops, my bad. Forgot how it was designed.

__________________
Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

I used heater hose for this and it works just fine. This is yet another example of a poorly designed $.50 part which makes a $$$ system unusable. When I bought my '88 560SL I spent hours debugging the ACC system, checking and changing parts until I discovered this little piece of foam all disintegrated behind the dash...literally 5 minutes later the ACC system was working as good as new after I stuck an 8" piece of heater hose in there.

The factory foam hose has a lining on the inside to keep it from sucking air through the material. I'm not sure the slit hose used for pipe insulation has that feature.

There is another piece of that same foam hose in a 123. It's the drain hose for the evaporator. When that one goes, you can get several inches of water in the rear floor pans.

__________________
Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

Why foam is used I don't know. I replaced mine with a hard plastic and it works fine.

http://www.peachparts.com/shopforum/showthread.php?t=70866&highlight=foam+dave

Read this post we discussed the foam Vs. hard tube.

Remember the sensor is at the opening of the dash. The tube is just pulling air thru it

Dave

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car