Both cruise and tach are inop on wife's 300SD. She hasn't said much about the tach, but the volume is rising over the non-functional cruise. All searches and threads seem to focus on the amplifiers as the source of most problems with either of these systems. The first thing I did was to install a new tach amp - tach still does not work.
Tach & cruise share a fuse (which I have also changed to no avail). Is there anything else that is common to both? Any suggestions as to where to start? Electrical systems are not my forte, but I have a sense that there is another common element (besides the fuse) that may be causing the problem. Any suggestions would be most welcome!!!

Jim

Do a search on here to find the addresses for the outfits that rebuild the cruise control amps. Get it rebuilt (approximately $150) and make her happy for a little while.

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Jim

I gather from your reply (and most all of what I have turned up through searches) that the amp is considered to be the root of almost all cruise malfunction.

My question was prompted by having come up with the same answer to the tach malfunction, I installed a new amp ($100) and the tach needle still won't wiggle.

Thought there might be a less expensive avenue to consider for the cruise; but then again, given the issues with these cruise amps, it probably wouldn't hurt to do the cruise amp as a starting point (and hopefully resolution).

Thanks, Jim

Cruise on my 190D was also inop but exhibited symptoms typical of amp trouble (random operation). A careful solder job appears to have resolved the problem for now, (thank you forum) and if it reccurs amp will go out for rebuild.

With the 300SD, cruise does absolutely nothing, as if the stem is completely disconnected from the system. Same story with the tach, which lead to my question (are there any common elements).

I appreciate the input,
Jim

Check out the paper Performance Products catalog... it had a blurb about diagnosing cruise controls problems.....and they used to allow you to buy the computer part of the system and insert it....and if that is not the problem return it unharmed.... since substitution is sorta the easy way for diagnosing these things....

Make sure there is a good connection at the tach amp. Pull the amp out and stuff something in the case behind the amp - a cigarette butt works - to push the contacts into the socket farther. Get some dielectric grease and put it on the contacts.

Most of the time the cruise problem is the amp. Occaisionally it is the actuator that sits on the engine - I have a used actuator for an SD if you want one.

Try a new CC amp first - I'll bet it will work. I use my cruise every day (new amp last year) and love it.

I think it's a coincidence that both are inoperative - they are both very common problem areas and not related.

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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer

I have had more success getting cruise controls to work than tachs but I have never really spent that much time trying to resolve tach problems.

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Jim

I tried this and more, would work for minutes or hours, then continue to flake out. That is, until about a week ago. Somewhat in frustration, I removed the tach amp (AGAIN) and squeezed each pin at the end with a small pair of visegrips. This sort of "knurled" the pins, raising the diameter in a few places. (I broke the tip off of 1 pin doing this, so be careful). Now, the tach has worked flawlessly since then, which is by far the best it's worked in 9 years

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I had the cruise amp repaired on my 1987 300TDT w/ OM603. The cruise control worked for a week, and then it suddenly stopped working again. I did some checking around and it turned out that the lever connecting the cruise actuator to the injection pump had come apart. The ends of the lever are plastic so when they get old they split and then they come of the metal rod.

The info. above only applies if the actuator is electric as on the OM603 and not the vacuum actuator used on the OM617 W123 chassis.

-Steve

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1987 300TDT smoke silver w/ burgundy leather interior
2000 VW Passat wagon indigo blue w/ beige leather interior
1985 Mustang SVO
1970 Chevrolet K10 fleetside, shortbed

Pete - thanks for the refresher course in electrical sockets 101. I have performed this operation at least a zillion times but have been so frustrated that I never even thought of it. As soon as the little lady comes in the drive with the SD, I am on it.

With an ounce of luck I will get the time this weekend to pull the cc amp and with another little bit of luck (am I pushing it or what?) maybe a solder job or a rebuild will solve that burning issue.

Again, I thank you all for the imput,

Jim

I tried to fix the amp by stuffing something (cigarette butts, cardboard, foam) in between the cap and the amp module… no worky still (needle bouncing around). Then I moved in further. I tried removing the silicon so that I could inspect the solder points and fix if needed. No luck, the silicon was very stubborn. Now the tach needle is completely dead…oops.

I can’t find a source to order a new/rebuilt tach amp. Does someone have a good lead?

Thanks again for all the contributions via all of your post to this forum I would be in the complete dark if it were not for this forum and at the mercy of my local indy.

http://www.gdl-online.com/begin.html

Cruise Control Repair Articles
http://www.peachparts.com/shopforum/diesel-discussion/123036-cruise-control-repair-articles.html#post883130



Have a great day.

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1985 300SD
1983 300D
1984 190D
2003 Volvo V70
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Jaoneill....I feel your pain in exactley the same place! Question for you....did your cruise and tach crap out at the same time?

I pulled my cruise amp and actuator and sent them off for repair, now the tach doesn't work (worked fine before). I too am wondering if there is a connection between the cruise and the tach.

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Mark
1983 300TD Wagon
Even a broken watch is right twice a day