I searched cruise control and didn't see anything like what I am experiencing. My 96 cruise control will work as long as I am setting it under 50mph. All functions will work properly, resume, accell, decal. If I run it up to 55 or 60 mph and try to set the cruise control, I feel it engage and immediently release. Any speed over 50mph it will not work right.
Has anyone else had this happen or know what the problem may be?

Have you just recently gotten new tires? I have seen a '99 E300 that the owner had recently purchased a new set of tires and one of them was not the correct size, preventing the cruise from working.

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Jim

I have just returned from a 1200km round trip in my 300SE (automatic gearbox) and seem to be experiencing the same problem.

The CC will work fine under speeds of around 105kmh. Above that, the acceleration function using the stalk will work, but the CC will not engage to hold a desired speed. When trying to set it at, for example, 130kmh, it will not hold speed, but once the car slows down to around 105kmh, the CC will engage.

Also, on two occassions a while following trying to set a desired speed, the car started accelarating on its own.

I have installed new tyres recently, but they are on original factory wheels and of the correct size.

Any ideas what could be causing this?

cheers,

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Mateusz
1986 126 500SEL
1986 126 300SE
1992 140 500SE
1996 124 E200T
1999 210 E320T
2017 205 C200T mit Schaltgetriebe!
2010 639 CDI 3.0

I've seen this sort of issue before.

The problem likely stems from tire sizes that are too different front to rear. The system can handle/expect a certain amount of difference between front/rear wheel speeds by changing to larger/smaller tires on either the front or the rear you can go beyond this difference.

What you want to do is

1) look up the stock tire sizes for the front and rear,
2) calculate the overall tire height of each set
3) find the difference between the two.
4) use that number a limit when choosing tires. your new front and rear tires should never exceed that difference.

I was able to help out a gentleman from Dubai with the same problem on his 2005 ML350. He had replaced the front tires with what was available locally. These were far too tall and put a 2" difference between the front and rear when the stock difference was only 0.14" His cruise would gut out at 80 kph. I had him replace one of the sets of tires bringing his difference down to 0.51" which re-enabled his cruise control at higher speeds.


This is for your 80s era 300SE?

The problem likely lies in the amplifier itself. The 126 generation used a single sensor in the transmission for speed as opposed to the original poster's late 90's car which uses multiple wheel sensors for speed. So tire size differences will have no effect on it.

The 86 300SE likely uses an 003 545 07 32 or an 005 545 05 32 cruise amplifier unit.

I recondition these units on the side so if you are interested drop me an email, JamesDean59@gmail.com and we can discuss it further.

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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


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