Dear all,

I experienced a strange behavior of the cruise control of my 1998 E-320. I speeded up to 65 mph and engaged the cruise control. It didn't want to hold the speed and I notice a slightly RPM surge - I felt a slight engine brake. However, the cruise control would engage at the lower speed but no more than 55 mph. I tried to search cruise control problem in this forum and founded only 2 other members experiencing the same symptom. However, there has no response to this problem. I am wondering if this problem is new to us with a newer model of Mercedes Benz. Any input, suggestion and help to diagnose this problem will be greatly appreciated. Thanks very much in advance.

- sdjumin

Good morning.
I knew if i read enough posts and did enough searching i would find someone else with tese same exact symptoms. I can see as of this time no one has responded to your question. Can you tell me if you found out what was (or is) giving you the problem. Any help would be appreciated.

Brian

Have the exact same symptoms. Holds fine at lower speeds, disengages if set at speeds above 55. Right now I have two circuit boards for Cruise Control in my hands, checking components, traces, solder joints, etc. (visually only, but under magnification). On the board in question, only item I have noticed is that a BZX diode has a bit of heat discoloration at the soldered leads. Don't know if this is due to previous repair or if it has significance. The other board holds any speed just fine, but will not resume if the brake ground has disengaged it. It will resume if disengaged at the stalk switch. Electronics is not my forte. Will report any findings, even if I just send one of them off to GDL and try the resolder technique on the other.

__________________
The Golden Rule

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

Check that front and back tires are same size and same
air pressure

funny..the tires on my car don't match. I hit a wheel in the road and blew both tires on the passenger side of my car and the replacements won't be here for a week so I have the spare and an extra tire on the car..would have never thought of it..thanks. When the new tires get here I will let you know if it resolves the issue.. Thanks again.

Brian

Tried resolder technique on ALL solder joints on the board that would hold speed but would not re-engage after brake light disengage; sorry to report that it has not worked yet. 25 watts, magnification, the whole bit.

__________________
The Golden Rule

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

My problem was solved. The size of my new rear tires didn't match that of the front tires. I got them replaced and the problem went away. Thanks for all replies.

Just read your reply sd. Thanks

Good morning guys,
just realized I had not writtent he final results. The problem was mismached tires. I had driven over a tire (still on the rim) on the hiway which blew the two passenger side tires. While I waited for the replacements to come in I had a different size tire on the back. Thanks for the help.

That happened to me too. Michelin MXV3 on the front and MXV4 plus in the back. Cruise control shut off at high speed. The MXV4's were slightly bigger which throws off the wheel speed sensors according to the dealer that fixed it. I am happy you found it before you spent a lot of time trouble shooting.