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Cruise control not working

Started by James R, 05 February 2007, 09:07 AM

James R

Any ideas why my cruise control isn't working on my 450SEL ? Can I fix it myself (i.e. is this a common problem and therefore has a "quick fix" ?) or is this a mechanic only job ?

Any help would be appreciated.

Many thanks,

James
1978 450SEL 6.9 - GONE!

1979 450SEL - GONE!

WGB

I assume you have the later cruise control which is similar to the one used in the 126.

I believe a simple place to start is the stoplamp bulbs in the rear. They are an integral part of the circuit and the wrong wattageand/or brand can be a problem.

Next check vacuum circuits and that the actuator works when a vacuum is applied.

Does the speed sensor at the back of the speedo still work ? and lastly the control unit itself is bolted above the brake pedal an in a spot which is as difficult to get at from above with the instruments removed as below.

www.pindelski.com is a site which is provided at a fee of USD$29 per year but has a full colour sequence in removing the unit, opening it and resoldering the connections (with great care) which crack at their soldered connections..

Saving that the unit needs to be rebuilt at a suitable specialist site.

Bill

BAR

Best way to be sure that it is the Cruise Control electronics unit itself that is at fault is to lift the lever up - to engage or increase speed.  If the car attempts to increase speed then it is most likely that the electronics unit is at fault and definitely not the vacuum unit.

As for removing and replacing, well as you have read, it is located under the steering column, you need to be fit and agile to get in there and undo the nuts etc.  Only has a single multipin plug for the electrics.

The major cause of failure is 'dry' solder joints and dead capacitors.

Contact Styria and he can supply a tested unit to you.


Good luck.

AMG69

I havent had mine working since I got the car BUT I have just received a reconditioned unit and will be fitting it - ie initiating the double reverse somersault with pike manoeuvre in the drivers footwell -  this weekend  ;D    Those of us who have doen this will know what a bloody back breaking job it is.  I ahve also replaced the actuator under the bonnet with a reco as previous owner has fitted wrong style clip to the top of it, closed the bonnet and shorted it out.  :-\  Anyway, as I'm heading down to Margaret River for the WA long weekend in March I am very hopeful I will have Cruise Control working!!

Now, must get back to some more wet and dry sanding of the "Leatherique" crack filler!
sigh....sitting back contemplating the next purchase..!

s class

AMG69,

I think your leatherique experiences are being closely watched.....

Both my 450SL and 280SE have non-functioning cruise control units.  Oh dear.  Can the body survive two such under-dash excursions in close succession?


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

James R

Guys - you are all very helpful. Thank you. Would someone be able to show me what the vacuum and actuator look like so I can follow the wiring from lever to machinery ?
Thanks again.

James
1978 450SEL 6.9 - GONE!

1979 450SEL - GONE!

bahnstormer109

When i got my 450 i tried the cruise for the first time and it worked but surged up and down instead of keeping a smooth even speed.

the second time i tried it it worked ok.

the third time i used it it didnt work at all.

any ideas on what might be the culprit here? shes now been into the mechanics to get all sorts of things fixed and has accrued a healthy bill, so im leaving non-essential things for later and trying to fix them myself.

cheers,
Paolo.
Paolo,
Brisbane, Australia.

72 300SEL 3.5
84 280CE
86 560SEL
86 230TE

WGB

Here are some photos I took when I removed my Cruise Control Amplifier from behind the dash.



The first View is into the dash with the instruments removed - the amplifier is in the middle of the two supports that hold the brake pedal assembly



Closer view of same shot



Amplifier hanging from loom after bolts have been released.


The vacuum actuator is under the bomnnet on the left side of the engine compartment toward the rear and has a long cable coming off the end of it which loops around the front of the motor and is connected to the throttle control at the centre rear of the motor.

Bill


AMG69

Well, fitted the Cruise Control Amplifier box Saturday and thendid a few 65km trips to and from the In Laws (Serpentine West) on the weekend and the Cruise Control. Worked perfectly.  Very different to electronic versions of today ofcourse!!  I note to cruise on 100kmhr its best to set it at about 110kmhr...by the time the car works it all out it set perfectly at 100!!  :D   SO, there you ahve it, after almost 3 years of ownership it works again - alll thanks to a rebuilt amplifier and a new vacumm actuator.
sigh....sitting back contemplating the next purchase..!

Andrew280SEL

Mine also surges up and down, but for some reason if I rest my foot on the throttle with the slightest pressure it works fine. Seems like the actuator is having trouble holding on or something... ::)
'79 280SEL- 560,000 Kms
'73 350SE- getting an AMG facelift
'79 450SEL 6.9

Bandolero

My 280SE did the same, just resting my foot slightly on the acc pedal and it was ok.
Later I replaced the amplifier under the dash and it is ok now with no surging.
However, sometimes it just wants to stop working by itself.
I give it a couple of minutes and it works again.
One day I will fit a new one.
Russell Bond - (Adelaide, South Australia)
1978 450SEL 6.9 .... #5166 .... 12/78 (Sold.) [url="//www.ezycoat.com.au"]www.ezycoat.com.au[/url]

13B

Resurrecting old topic here....

This weekend I'm going to pull out the cruise control box because all the testing I've done after reading cruise control stuff on this site indicates mine is tired and in need of re-soldering all its joints.  When it works it maintains the correct speed without much surging.

The contorsion will be fun, but can someone list me all the tools I'll need to remove the box - I'll put them on the floor (next to my head) before starting.  I'm trying to expedite having to get in and out of the contorsion over and over again trying to find the right spanner, screwdriver, hex key or whatever.  WGB if you could email me the 3 pictures from this thread which are gone?

Thx

I.
450SEL 6.9 #5440 = V MB 690 , 450SE # 43094 = 02010 H , 190E/turbo # 31548 = AOH 68K

WGB

I think you will need a 10mm socket and a Phillips head screwdriver.

The amplifier is attached to a bracket by one phillips head screw and the bracket is attached to the brake pedal support by one 10 mm bolt. (I think that is the correct way around).

The wiring loom is also connected to a socket fixed to the bracket.

The easiest way to get it is to undo the bracket and drop the whole lot and then unscrew and unplug the amplifier.

From memory the 10 mm bolt is at the rear of the bracket behind the body of the amplifier but will check and e-mail you my pictures when I get home tonight.
I have since removed another one from the wreck I have and will take some extra photo's of the bracket and the internals of that one.

Bill

Bandolero

Phillips Head screwdriver and 2x 10mm spanners.

I have done this job a few times. Easy, just slide the seat back and away you go.
It does help that I am short   ;D
Russell Bond - (Adelaide, South Australia)
1978 450SEL 6.9 .... #5166 .... 12/78 (Sold.) [url="//www.ezycoat.com.au"]www.ezycoat.com.au[/url]

WGB

Hi 13B,

Fiddled around with the album and the photo's returned.

I will put them in again just to make sure you get them

1. View through empty instrument binnacle with Amplifier in centre of picture



2. Close up view of Amplifier in position



3. Amp hanging on loom with fixing points labelled




Bill