Cruise Control

[Michel]

I am sure it must have been discussed before...

My cruise control doesn't work... never did when I got it.

Where do I begin?

Do we know anyone who fixes them, replaces them, etc...?

 

[B13]

Although I've been slack, and not done mine (since its intermittent and most of my driving doesn't offer the opportunity to use it), but as I understand it the system rarely has a problem other than the control box burning out the odd component or suffering from dry solder joints.

Basically if while driving you lift the CC lever upwards and the car accelerates like someone has stood on the accelerator then its all ok and the problem most likely is inside the control box.

Some people have had success by removing the box, taking out the circuit board, examining and replacing any burned out components (most often resistors) and then starting at one end and re-solder every connection on the board, which should fix any dry joints.

Its what I would do before trying anything else...

Ian.

 

[Michel]

Although I've been slack, and not done mine (since its intermittent and most of my driving doesn't offer the opportunity to use it), but as I understand it the system rarely has a problem other than the control box burning out the odd component or suffering from dry solder joints.

Basically if while driving you lift the CC lever upwards and the car accelerates like someone has stood on the accelerator then its all ok and the problem most likely is inside the control box.

Some people have had success by removing the box, taking out the circuit board, examining and replacing any burned out components (most often resistors) and then starting at one end and re-solder every connection on the board, which should fix any dry joints.

Its what I would do before trying anything else...

Ian.

That sounds like a great starting point....
Thanks

 

[TJ 450]

The problem of surging is almost entirely related to failed capacitors in the amplifier. Capacitors of the type employed, although extremely good quality when new have more than likely wandered too far out of tolerance after 30yrs of use in the harsh environment of the vehicle. The values of these capacitors are critical for the proper operation of the analogue circuitry in these amplifiers.
The best approach here is to replace all capacitors on the PCB with the equivalent type and value, which you will have to obtain from a proper electronics shop. It is advisable not to purchase cheap electrolytics as they will fail again.

If the cruise is not functioning at all there might be a problem with switches/wiring or the bellows.

Tim

 

[Michel]

The problem of surging is almost entirely related to failed capacitors in the amplifier. Capacitors of the type employed, although extremely good quality when new have more than likely wandered too far out of tolerance after 30yrs of use in the harsh environment of the vehicle. The values of these capacitors are critical for the proper operation of the analogue circuitry in these amplifiers.
The best approach here is to replace all capacitors on the PCB with the equivalent type and value, which you will have to obtain from a proper electronics shop. It is advisable not to purchase cheap electrolytics as they will fail again.

If the cruise is not functioning at all there might be a problem with switches/wiring or the bellows.
Tim

So......
where would you begin looking Tim?

 

[Des]

Thats a big MM


try these

Cruise Amp Repair

http://www.mindspring.com/~houlihan/merc/cruise.htm

http://gdl-online.com/begin1.html

 

[TJ 450]

What happens when you push the stalk up to the "accelerate set" position whilst driving? If it doesn't work at all, the first thing to check is you RH brake light bulb, believe it or not. The entire system grounds out through that bulb. The second thing to check would be that the module is actually there, someone may have removed it. The module is located in the back-breaking position above the steering column on a bracket.

If it responds by going full throttle, or surging, the capacitors in the amplifier module are at fault.

The system itself is actually quite basic and faults are usually either the module (most common), the Bellows (cylindrical device near the LH bonnet hinge) or the wiring/switch gear (least likely). The control cable could be disconnected from the regulating linkage.

Tim

 

[BAR]

The majority of cruise control 'failures' are caused by the solder joints becoming 'dry jointed'.

SO take out the box and gently pull back the locking tabs and the PCB will slide out.

As identified in other post it is also wise to take the PCB to an electronic component store and match the older capacitors with equivalent new items. Also buy a solder sucker to aid in removal of the old solder. Remove the capacitors and replace with new units. Then remove the solder from other joints and resolder one at a tme.

You should have a total expenditure of <$40 and the biggest chance of a working cruise control.

 

[Michel]

Thanks guys....

I have a feeling this is beyond my capabilities (and my patience).

Does anyone know somebody who can fix it (on the side)

Not interested in even contemplating talking to an MB dealer

 

[BenzBoy]

Have you priced a new control unit? Styria may have a known unit (second hand) or you could try my fellow.
Regards,
BenzBoy

 

[Michel]

Have you priced a new control unit? Styria may have a known unit (second hand) or you could try my fellow.
Regards,
BenzBoy

You are full of good ideas old chap

 

[Styria]

I think most of us know that the price of a new module is in the region of a minimum of $1k. - that was the price about two years ago - someone will be able to tell us today's price.

Some while ago, I had some units fixed at 'discount' rates, but the success rate was such that I gave up selling them on an exchange basis. You need a professional Instrument Repairer to do the job, and if I utilize the guy I used to use, you're looking at $350.00 exchange, 12 months warranty and no questions asked in the event of a claim. I had the unit in Gleaming Beauty rebuilt some four years ago, and it has only just started to act somewhat indifferently some two months ago when last used. Regards Styria

 

[Michel]

The majority of cruise control 'failures' are caused by the solder joints becoming 'dry jointed'.

SO take out the box and gently pull back the locking tabs and the PCB will slide out.

As identified in other post it is also wise to take the PCB to an electronic component store and match the older capacitors with equivalent new items. Also buy a solder sucker to aid in removal of the old solder. Remove the capacitors and replace with new units. Then remove the solder from other joints and resolder one at a tme.

You should have a total expenditure of <$40 and the biggest chance of a working cruise control.

I guess I better find someone with electronics knowledge and soldering skills ...


ANY VOLUNTEERS?

 

[Styria]

What Bar says is probably spot on. On the other hand, you need someone that's totally familiar with the task onhand - the last thing one would want is that the car accelerates wildly when, in fact, you're trying to cancel the operation of the unit ! One needs to really know what they are doing -the responsibility is enormous. Just my opinion, Styria

 

[WGB]

I "repaired" my own in my 4.5 with mixed results by carefully re-soldering all the joints and it works after a fashion but the speed wanders.

My 6.9 had a "reconditioned" amplifier fitted by AMG69 before I purchased it and it works but the speed drops to about 5 km below the set speed but stays stable after that (You just overshoot a bit when you first set the speed).

Apart from the development of dry soldered joints there are 14 capacitances on the circuit board which dry out and need replacement and as I understand it some cannot be replaced by exact spec modern and available equivalents.

The end result is they never quite perform right.

I have accumulated a spare amplifier from a wrecked 450 I have and am going to attempt to source as close to correct capacitators as I can and see what sort of result I get but this is not a present day must do.

1) The 6.9 tends to be somewhat coarse in it's action due to the vast amount of torque in the engine and a little "stiction" in the operating cable. In a 280 when new the cruise control was a very sweet and well behaved device.

2) It is better not to fiddle with the internals of the amplifier unless you are as brave (foolish/foolhardy) as me as most of the electronic reconditioners will not touch them or warranty a repair if previously tampered with.

3) Styria - unlike Jaguar cruise controls of the period when M-B ones fail they tend to shut down and I have never seen an M-B accelerate when failed. I did own a Series 3 XJ6 of 1984 vintage that did do that but at least it had an on/off switch on the console when uncontrolled hedonism (unrestrained enthusiasm) reared it's ugly head. I tracked the fault in that one down to a broken wire in the control lever on the steering column.

Bill

 

[TJ 450]

Hi Bill,

When you replace the capacitors, you could give RS components in Osborne Pk. a try... they have a huge catalogue and probably have those "in-between" values required. Again, you should refrain from using electrolytics at all costs... the tolerance is simply too wide for the application (you will get surging). Film capacitors are the go here and above all they will hold their values indefinitely.
It will be better than new.

Tim

 

[Michel]

hmmmmmmmmmmmm

I guess there are no volunteers...

 

[Des]

hmmmmmmmmmmmm

I guess there are no volunteers...

Well with the potentual crash you could have as a result of it not working correctly I new unit would be the safe option.

You would also expect a new one to stay working for 10-15 years.


Granted $1k is not pocket change, but if you are going to keep the car it is an investment in the future of the car.

 

[Lukas]

Hi Michel and others,

The cruise in the blue 6.9 at least doesn;t work, so I'll be trying these things eventually, and I do have a little electronics experience, so will try the resolder / replace components approach on mine eventually. If I don't break it completely and it actually fixes it, happy to give others a go. However, we're talking January at the very earliest here sorry.

Perhaps you could talk to your local Jaycar store - they might just know a hobbyist that will re-do the electrics for you at a reasonable rate?

Lukas

 

[Michel]

Hi Michel and others,
If I don't break it completely and it actually fixes it, happy to give others a go. However, we're talking January at the very earliest here sorry.
Lukas

Quite happy to wait for whatever time you can (unless something comes up in between)