With respect to a malfunctioning cruise control, my understanding is that, if the switch or actuator is bad, the cruise control simply won't work.

My symptoms are as follows: when cruise control is engaged, the car lurches intermittently: speeds up, slows down, speeds up, slows down, OR it gradually accelerates and then slows down. This happens whether I push lever up (accelerate position) or pull in (set current speed position). Whenever I disengage the CC, it successfully disengages.

From everything I've read, it seems like a VIRTUAL CERTAINTY that I have a bad amp that needs to be repaired or replaced.

Do you agree?

Thanks.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Nothing is a "virtual certainty" without proper testing.

However, with the symptoms provided, the cruise amp is the most likely culprit. When the actuator fails, it usually won't allow any movement of the rack.

BTW, I like to translate the word "virtual" as follows: "not absolute".

Whenever you hear the talking heads use the word "virtual", you can bet that the statement following is not a certainty and they cannot define the level of uncertainty.

Thanks. Since I'm not a DIYer, I'm trying to figure out a way to avoid a diagnostic charge. I figure if there's a high probability that the amp is the culprit, I'll simply have it removed, get it resoldered, and put it back in. Obviously no guarantees....but neither am I out much money.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Resoldering the board may or may not solve the problem. You roll the dice with that. I've always rolled snake eyes.

Or I might see if I can simply find a good used part....my tech claims they're available. I'm just really reluctant to drop $450 for a new amp.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Scrounge up a known-bad one to use as a core for GDL, save yourself a few bucks at least...

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1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

A search usually turns up these folks: http://www.gdl-online.com/testproc.html

This is a test procedure they have to determine the likely failed part and their repair of the parts is much less than $450. However, it is my understanding that they turn away units that have been "worked on".

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Sam

84 300SD 350K+ miles ( Blue Belle )

I think that the problem is in the actuator. I have found that the actuator can have worn spots and will surge or have worn traces on the feedback and will give you fits. The actuator causes more problems than the amp and it is mostly the cause of the amp going bad except for the rare cases of cold solder joints in the amp.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C

A proper re-build of a cruise amp not only requires re-soldering but also replacement of capacitors (which age over time) and some transistors as well. You have to seek modern substitutes for the old devices on the board. Simple re-soldering may OR MAY NOT work as the cruise amp is an analogue device and its operation depends on the components having the right electrical characteristics. Capacitors and some resistors change their performance over time. And you can blow a transistor through excessive heat if you are not careful.

I made the mistake of dismissing Brian Carlton as a perfectionist and bought a so-called "working" unit on eBay for $50. It works, kinda, some of the time. So Mr Carlton is correct!

So GDL-online is the way to go. The test procedure is quite involved and it's your decision whether to spend your time and money on testing or simply get them to re-build the amp. There are other re-build outfits that advertise in The Star and so on, but I do not know if they are any good.

I've bought four used amps over several years. One worked for about six months. Others might have better luck than I.............

I would give GDL a call, but I don't know if they work on post-85 amps. They will not accept a core that's been hacked up (a good thing if you a buying one from them). I recently bought a rebuilt amp and a new actuator from them (for my 82), they work perfectly; cost about $600 total.

I have purchased two complete units from Peter at GDL and they work flawlessly. You may have to wait a month is he is backlogged, but it will be worth it.

John

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Certified Registered Nurse Anesthetist (CRNA)
2002 F250 powerstroke with Plantdrive WVO conversion
1983 300SD 190K miles ,sold
2006 E320 CDI

The actuator cntacts get greasy inside, causing this. This happened to mine. It is possible to clean the contacts, but its like surgery.

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1981 300SD 512k OM603

Fortunately, he had mine in stock, so I had it in a few days.

Had a pleasant and lengthy conversation with Peter at GDL. What a knowledgeable and helpful guy! From my description of the problem, he is quite convinced that it is only a problem with the amp, that it's unlikely that I have a problem with the actuator (contrary to the opinions of some others), and this from a guy who freely acknowledges that, in some cases, the actuator can be the problem (http://www.gdl-online.com/test021.html). But he said that, once he opens up the amp, he'll be able to ascertain whether there are any actuator-related problems.

So my options are:

1. Get a new amp for about $350.
2. Get a used amp for under $100 (found one for $85 w/6 month warranty)
3. Get mine simply resoldered for $40 (a crap shoot).
4. Get GDL completely to recondition mine for around $215.

I'll probably go with option 4....would seem to be the most cost effective way to solve the problem "permanently."

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife