Author Topic: Cruise control actuator testing  (Read 5196 times)

1980sdga

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Cruise control actuator testing
« on: 28 November 2011, 06:08 PM »
I have the later model vacuum actuator:



I wanted to bench test the actuator using the method Koan outlines here:

http://forum.w116.org/mechanicals/ok-all-sorted-thank-for-the-replies-please-ignore-this-thread!!/msg39658/#msg39658

Can I apply vacuum to the actuator using a pump and still apply voltage to the pins to test it?  Do the electrics control a vacuum valve inside the actuator?

If the car cooperates I think this'll be my next project  ;)
Jon


Little by little I have grown fond of the infamous Auto Temp II we have in our 116's

koan

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Re: Cruise control actuator testing
« Reply #1 on: 29 November 2011, 12:09 AM »
Can I apply vacuum to the actuator using a pump and still apply voltage to the pins to test it?  Do the electrics control a vacuum valve inside the actuator?

That should work but ideally you need a reservoir of vacuum and a variable power supply to vary the current through the actuator. With a setup like that the movement of the cable would be in direct proportion to the current. Max current is about 300 mA from memory.

There's a clever little see-saw arrangement inside where the current tilts the see-saw one way and the diaphragm tilts it the other way through a spring.

When the current wins and the see-saw tilts it opens a port to admit vacuum to the diaphragm chamber which compresses the spring and brings the see-saw back to level and closes the vacuum port.

If the current drops the see-saw tilts to the spring side and opens a vent allowing air into the diaphragm chamber releasing the spring allowing the see-saw to return to level closing the vent.

I know all about this, I pulled a perfectly good unit apart rather than testing it on my car first. Stupid!

What do you suspect is wrong with your unit?

koan
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Big_Richard

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Re: Cruise control actuator testing
« Reply #2 on: 29 November 2011, 01:16 AM »
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« Last Edit: 23 January 2013, 02:42 AM by Major Tom 6.9 »

koan

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Re: Cruise control actuator testing
« Reply #3 on: 29 November 2011, 01:29 AM »
Did you take any photos ?

No but I've still got it, I'll do some pics on the weekend.

koan
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1980sdga

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Re: Cruise control actuator testing
« Reply #4 on: 29 November 2011, 10:32 AM »
I'm pretty sure it's OK. I just wanted to test it.

My cruise was working but it exhibited the symptoms of a bad amp. I'm going to have to relocate the actuator because my AC accumulator is in it's spot  ???

I have a vacuum pump/reservoir rig that I used when sorting my ACC and door locks without having to run the engine. I figured I could use it to bench test this accumulator before going to the trouble of installing.

I have a 12v power supply but no way to vary the current. Any input on this?

Thanks!  I'm looking forward to seeing some pics of the inside of this thing!
Jon


Little by little I have grown fond of the infamous Auto Temp II we have in our 116's

koan

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Re: Cruise control actuator testing
« Reply #5 on: 29 November 2011, 11:50 AM »
My cruise was working but it exhibited the symptoms of a bad amp.

I get aggressive over and undershoots of speed control which I think is the actuator. I tested it on the car and couldn't get smooth operation.

Quote
I have a vacuum pump/reservoir rig that I used when sorting my ACC and door locks without having to run the engine. I figured I could use it to bench test this accumulator before going to the trouble of installing.

I have a 12v power supply but no way to vary the current. Any input on this?

The actuator resistance spec is to 10 to 22 ohms.

An instrument cluster dimmer rheostat in series with the supply should be able to handle the current I think. At minimum resistance the current might be too much to a 10 Ohm actuator but it should reach maximum travel well before that with good vacuum.

Quote
Thanks!  I'm looking forward to seeing some pics of the inside of this thing!

I'll do it (after I finish painting a cornice in 4 colours, hanging a few pictures and helping with curtains, the list will probably grow before the weekend - if I'm really really lucky...).

koan
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KenM

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Re: Cruise control actuator testing
« Reply #6 on: 30 November 2011, 01:54 AM »



There's a clever little see-saw arrangement inside where the current tilts the see-saw one way and the diaphragm tilts it the other way through a spring.

koan

It's called a Wheatstone Bridge, and there endeth my useful input to this thread. I also am interested to see any photos or further information to be found.

Edit: Apologies for wrong information, as has been correctly pointed out to me a Wheatstone Bridge in fact is a device to control voltage, impedance etc in an electrical circuit whereas the cruise actuator is more of a negative feedback loop type arrangement.

Cheers,
« Last Edit: 30 November 2011, 01:44 PM by KenM »
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koan

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Re: Cruise control actuator testing
« Reply #7 on: 02 December 2011, 08:57 PM »
I'll do it (after I finish painting a cornice in 4 colours, hanging a few pictures and helping with curtains, the list will probably grow before the weekend - if I'm really really lucky...).

Pictures and description posted in gallery, W116.org Gallery » Garage » koan's bits » VDO Vacuum Cruise Control Actuator


Click Me!


And guess what!   Dale is away for the weekend so painting, picture hanging and curtains have taken on an exceedingly  low priority :)

koan

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Big_Richard

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Re: Cruise control actuator testing
« Reply #8 on: 03 December 2011, 04:59 AM »
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« Last Edit: 23 January 2013, 02:42 AM by Major Tom 6.9 »

koan

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Re: Cruise control actuator testing
« Reply #9 on: 03 December 2011, 06:13 AM »
Its always quite interesting to see how things "got done" in the days prior to the dirt cheap electronics that now rule our world.

Like the old ways.

Dale is my partner of 32 years...

koan
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1980sdga

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Re: Cruise control actuator testing
« Reply #10 on: 03 December 2011, 07:14 AM »


And guess what!   Dale is away for the weekend so painting, picture hanging and curtains have taken on an exceedingly  low priority :)

koan

Pick the low hanging fruit. Maybe hang a picture.  BE A HERO!
Jon


Little by little I have grown fond of the infamous Auto Temp II we have in our 116's

koan

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Re: Cruise control actuator testing
« Reply #11 on: 03 December 2011, 12:26 PM »
Pick the low hanging fruit. Maybe hang a picture.  BE A HERO!

Great idea, good thinking!

koan
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KenM

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Re: Cruise control actuator testing
« Reply #12 on: 03 December 2011, 02:12 PM »
Thanks for the pics Koan, very informative. I found a link to a company in California that rebuilds cruise control and climate control systems, might be of use to somebody.

http://gdl-online.com/differences.html  Other info on their site could be useful too.

Cheers,
Mexican girl: 'We could go for a walk outside and you can kiss me on the verandah'
Chevy Chase: 'On the lips will be fine'

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1980sdga

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Re: Cruise control actuator testing
« Reply #13 on: 04 December 2011, 09:22 AM »
Thanks guys! Armed with just enough information to be dangerous, I'm off on another adventure  ;D

I installed the actuator this morning.

The small vacuum line on the actuator was plugged and it was still holding vacuum after 8 hours when I pulled the cap. It continued "hissing" while I fumbled around and placed it on the actuator nipple so I imagine my vacuum reservoir system is good to go.  I had some pretty serious vacuum problems when I began sorting the car so I'm a little spooked any time I bring another system online  :P

I'm going to take it on a test drive after checking the door locks again.  I figure if my door locks still work after a few hours then the actuator isn't giving me any problems on that front.

Any advise on adjusting the cable where it connects to the throttle?  For now I have it adjusted so the pad on the cable is just touching the throttle linkage.

I believe it had trouble "locking" onto the speed before but I can't really remember  :-\  I was sorting a bunch of stuff at once and decided to just plug the cruise stuff to rule out vacuum leaks at the actuator.

Since the threaded "vacuum" line is just a vent that leads into the cabin why go to all the trouble to put threads on it?  Maybe a failsafe of some sort to be sure the vent isn't plugged?
Jon


Little by little I have grown fond of the infamous Auto Temp II we have in our 116's

koan

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Re: Cruise control actuator testing
« Reply #14 on: 04 December 2011, 10:48 AM »
Any advise on adjusting the cable where it connects to the throttle?  For now I have it adjusted so the pad on the cable is just touching the throttle linkage.

The book says the cable should be adjusted to be just clear of the throttle linkage.

Since the threaded "vacuum" line is just a vent that leads into the cabin why go to all the trouble to put threads on it?  Maybe a failsafe of some sort to be sure the vent isn't plugged?
[/quote]

Yes, it's an odd one that.

koan
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