Cruise control not working

[David]

Unfortunately I do not know how to include the Jpg photos but here is a tip from a friend in Cape Town:
With age, the Tempomats in 116's and 107's become "forgetful" and do not maintain the set speed. This is often due to the "memory" condensors drying out internally, and then performing inconsistently with temperature changes.

The Tempomat Speed Control housing is located above the steering column, and once the 10-pin plug and outer casing is removed, you can slide out the PC board (see photos).

The condensors in question are numbered 1 to 8 in photo 5.

The list of values applies to MB 001 545 2032 to 412.203/1/3 VDO 117509 116 2.80, and may be difficult to obtain.

First check the values before removal! You can perhaps use higher voltage units (eg. 35V instead of 10V).... but not the other way round.

On the bottom side of the PC board (photo 6) there are small "+" marks, and it is important not to reverse the new units because they will explode! With the Tantal condensors, the "+" is on the right leg pointing downwards when reading the script on top.

The above procedure should solve the problem, but it is for information only and at your own risk. No responsibility can be assumed for failures!

Joburg Oyster

[frikkie]

Unfortunately I do not know how to include the Jpg photos but here is a tip from a friend in Cape Town:
With age, the Tempomats in 116's and 107's become "forgetful" and do not maintain the set speed. This is often due to the "memory" condensors drying out internally, and then performing inconsistently with temperature changes.

The Tempomat Speed Control housing is located above the steering column, and once the 10-pin plug and outer casing is removed, you can slide out the PC board (see photos).

The condensors in question are numbered 1 to 8 in photo 5.

The list of values applies to MB 001 545 2032 to 412.203/1/3 VDO 117509 116 2.80, and may be difficult to obtain.

First check the values before removal! You can perhaps use higher voltage units (eg. 35V instead of 10V).... but not the other way round.

On the bottom side of the PC board (photo 6) there are small "+" marks, and it is important not to reverse the new units because they will explode! With the Tantal condensors, the "+" is on the right leg pointing downwards when reading the script on top.

The above procedure should solve the problem, but it is for information only and at your own risk. No responsibility can be assumed for failures!

Joburg Oyster

Hey, David!

Any chance you can mail those jpg's to me? hein dot bosman at gmail dot com.

Thanks mate!

[gregdeklerk]

Ja, me too please.

P.S. David/Dawie, welcome to the forum.

[Gerard]

Hi
Sorry for resurrecting an old topic.  Could someone forward on the details of the new capacitors to me?  I have re-flowed every joint on the board and the CC works intermittently, cuts out a lot.  I would like to try new capacitors if I knew the values of them, and the pics of where they go.
Thanks
G

[koan]

Very much doubt if new caps will fix a cruise control that works intermittently and cuts out a lot.

Is this a new problem?

Did reflowing all the joints fix anything?

I would look for a wiring problem.

koan

[Gerard]

Hi Koan,
Before I reflowed the joints nothing worked except the accel toggle would send the accelerate signal and the car would speed up.  So I guessed that the actuator etc was OK, and the problem was in the board.  When I replaced the re-flowed board, I took it for a spin around town, but traffic was not so good, so I couldn't get a good chance to evaluate the system.  It did work, but it was hard to engage.  I put it down to the speed not being high enough.
Yesterday I was on a motorway and tried it a few times.
It did manage to settle on a speed on some occasions, but not the speed I was driving at, usually a lower one.   It will turn off ok, but accel or decel will cause it to disengage altogether.  Not sure whats next?
regards
G
PS just bought the car 2 months ago.....loads of little jobs to do on him.....1980450SEL....icon gold too, just like one or 2 on here!

[TJ 450]

What about a poor connection at the brake light bulbs? I think it's the RHS that completes the circuit to ground.

Tim

[koan]

I'd still be looking at the board, re-examining it for solder dags or flaky bits of solder floating around.

If any joints look dry, suck the solder off and add more. Always better to resolder with new solder rather than supplement old solder

The usual problem with aging caps is a functioning unit that slowly drops speed, you are not quite there yet.

Also check the switch wiring and meter it out if possible.

My unit will work from around 25kmh, doing very aggressive acceleration, dropping back gears to get to a resumed spped.

The units are designed to drop out if speed drops too far below the set speed.

Is it the early VDO electric servo or later vacuum model ?

koan

[Big_Richard]

The units are designed to drop out if speed drops too far below the set speed.

Thats precisely how the caps can make the cruise control intermittant - from memory, the heart of the system is a voltage comparitor chip, which compares stored voltage (speed) against current speed (voltage). the remembered speed (voltage) is whats stored in a couple of the capacitors, dont remember which and when these are crap the stored speed (voltage) discharges quickly.

been a long time since i worked on these things, mine worked perfectly for 3 years after a recap/resolder but now has the same symptoms all over again and i no longer care. The box in operation does get quite hot and i suspect its the cyclical heating of the board thats killing them or the drying out of the electrolitic caps becuase of the heat. I did not use high temperature rated caps.

[TJ 450]

If the caps are too far gone, the cruise control won't work at all... this is what I've experienced. It makes sense that if they are marginal, it would work occasionly.

Tim

[goldacre]

If you want out from the Tempomat system have a look at these companies...

Here is a company that does the aftermarket cruise control (CC) replacement. Here is the link:

http://www.autron.com.au/newweb/index1280.htm

These people supply CC units that can be wired into the existing stalk on the steering column , these are the people who make them:

http://www.rostra.com/

Go to the Universal CC window.

When i was looking to get one fitted they put me on to an Auto electrical place in Melville Western Australia. I did not get it in the end as my mechanic sorted out the issue i was having.

G

PS. i was quoted $700 (30 April 2008) 

[Big_Richard]

PS. i was quoted $700 (30 April 2008) 

Wow, thats reasonable. (sarcasm detection meter overload)

my CC worked 3 years for a grand total expenditure of $2.90 worth of componentry. 

[TJ 450]

I know which option I would choose.

Modern cruise control would be nice though.

Tim

[Gerard]

Hi Guys,
Thanks for all the replies.  Good to read them.
Koan, I'm fairly sure its vac as I remember a vac line going to the actuator.  I'll check the next time I look (1980 car).  I reflowed the joints, with extra new solder.  Didnt go to the trouble of sucking off all the old solder though!!  I then inspected the card and reflowed any suspect joints, then inspected again.  I'm fairly happy the board joints are OK.
I did have a look at the tail light bulbs too.  They seem fine, nice clean connections.

Does anyone have the values of the caps?

My unit seems to work somewhat.....but will not engage at the current driving speed.  I activate the tempomat, then let the car decelerate, then the cruise will take over.  Sometimes it operates at 2-3mph below set speed, sometimes it goes down 10mph before activating.  Once activated it seems to work fairly well.  But ACCEL or DECEL just causes the unit to disengage.

Hmmmmmm!!!
G

[koan]

My unit seems to work somewhat.....but will not engage at the current driving speed.  I activate the tempomat, then let the car decelerate, then the cruise will take over.  Sometimes it operates at 2-3mph below set speed, sometimes it goes down 10mph before activating.  Once activated it seems to work fairly well.  But ACCEL or DECEL just causes the unit to disengage.

A momentary flick in th ACCEL SET direction should latch the current speed, there will be some slowing due to the design of the servo but the speed should return to the latched speed. In practice my unit used to settle at a speed pretty close but not quite.

As far as the caps go, I have seen two board layouts but both have two 47uF 16V electrolytics in silver cans on them. I'd just replace those two.

On one corner of the board is a relay, a 4 pin FET in a transistor package and a capacitor, that's the capacitor that stores the speed. Looks like silver mica or something else high quality, wouldn't touch it.

koan