Cruise Control troubleshooting

[Benjamin Gell]

I'm trying to repair my '88 factory cruise control. I replaced a faulty vacuum line, and had to adjust the clutch vacuum relief switch. I've been completely through the Bentley tests, and passed all except the resistance test of the inductive speed sensor on the speedo. Did them all about 3 times.
I'm not sure I'm using my meter correctly, for the sensor resistance test but it reads "1". I had it set to the "200" range.
I assume I need a sensor, but can't find one. Any suggestions?
But, that may not be the problem:
When I ran the vacuum pump continuously, the vacuum servo on the throttle did contract a lot, but not quite enough to move the throttle unless I assisted it a bit. I thought maybe it wasn't supposed to pull hard enough until in actual use with the computer plugged in and all, but maybe that's wrong?
From what you posted, it sounds like it should pull the throttle all the way open if the vacuum pump is run continuously. This scheme would mean that the actual throttle position is adjusted by intermittent bursts of pump actuation which opens the throttle and, to allow the throttle to close a bit, intermittent opening of a vacuum relief valve. Is this right?
So, should I look for why the vacuum isn't stronger before I try to solve the problem (if it even exists) with the speed sensor? I ask because one poster said he had about 3 well-working cruise controls, and the resistance figures for the speed sensors were all over the map, and not within Bentley's specs.
Thanks for any help you can give.
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'88 Vanagon Wolfsburg hardtop, 10cent WBXaust.

"My God! Its full of stars!" oh, wait...that's gravel.

[insyncro]

Sounds like a weak pump or leaking actuator.

I have found with some of my converted vans, that the pumps do wear out and cant pull enough as the Subaru throttle body is dual chamber on the EG33s.
I swap in a fresher pump and bingo.

Dont see why it couldnt happen as per stock.

[dan vandenheede]

Good timing on thread, I just finished troubleshooting that exact cruise on my van. It is an a.r.a brand, which went out of business a long time ago. I couldn't find a wiring diagram either, so like you traced wires. My brown wire tied into plug on distributor (hall sensor???). And I believe that is where the speed signal comes from, no vsS and no magnets. Mine turned out to be bad connection. The power light should come on with ignition and cruise switch both on, engaged light should come on when set button is pushed and power light is on. My engage light wouldn't come on until I redid some connections from stalk to control unit. Works great again now. Note that it won't engage at idle or revving in neutral, need to be moving. I don't know how it knows, but mine will only engage a second without moving and kick right back off. As others have said, you may be able to pull the speed signal from tach, same basic principle.
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Bonnie, '68 vert and Clyde, '89 syncro adventurewagen. Also '69 Sportsmobile looking for a name.

[dan vandenheede]

Btw, others have mentioned vacuum, none on this unit, it is electronic, bit ahead of it's time I would say. There is a electric servo in that black box that pulls the cable hooked to the throttle. Mine has been very accurate and steady on speed, and up until I took the dash all apart tp get to my heater core, very reliable. I apparently had stressed a connection putting everything back together, but all is well again.
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Bonnie, '68 vert and Clyde, '89 syncro adventurewagen. Also '69 Sportsmobile looking for a name.

[insyncro]

The stock system uses a Reed switch connected to the back of the speedometer housing.

[VikingWagen]

"resistance figures for the speed sensors were all over the map"

My cruise control just started acting up with symptoms similar to a previous poster where the speed setting is much lower mph than intended. So I went thru the Bentley cruise control trouble shooting procedure which told me the speed sensor was bad. If the reading for that sensor is not a reliable means of checking its function, then how do I know if the speed sensor is faulty or not?

I will double check the brake/clutch switches, brake lights and see if the vac motor actually moves the moves the diaphragm properly.

PS Great writeup davevickery!

[davevickery]

I was going to revise it for a few simpler instructions but now I forgot. I just had to troubleshoot the cruise on my new van and it started coming back to me.

It always seems to be the clutch/brake switches. Any bit of leakage when you remove them and blow through them is a problem. They have to seal perfectly.

Another simple test is to suck on the hose going to the vacuum bulb. You can suck in on it and watch the throttle move. Hold your tongue on the tube and the bulb should not leak back up. But I don't think those bulbs get holes very often.

When I did that test above though, I found that the arm that connects from the bulb to the throttle body was moving and not the throttle. There is an adjustment to tighten it up. But testing it with the suck test is good because it would find a variety of problems with the mechanism.

I also think you can test the brake/clutch switches by clamping off the hose that comes from them at the pump. If they are the problem, you are bipassing them by clamping them off. I haven't tried it though.

[JDEL]

I have a 1990 Multivan Vanagon. It has factory cruise control. I replaced all the hoses in the engine compartment and inspected the diaphragm. I reconditioned the switch at the brake pedal (automatic) by cleaning the connections and putting vasoline on the seal. And it worked! for like 3 seconds..... What should I check next?

[davevickery]

I don't think you can do much with those peddle switches except replace them. I'd pull it out, blow into it and see that it seals perfectly. Then make sure it is adjusted so it closes with the peddle up.

You could check the mechanical parts at the throttle. If it worked for just a few seconds, maybe the snap popped off the throttle ball or something else came loose.

I would look at those first but the Bentley troubleshooting routine would be next. Mine is working great on my new van, and what a nice convenience it is.

[0to60in6min]

@JDEL...

you may want to check the play of the linkage of the CC slider and CC vacuum actuator... it should have very little play..

you could adjust the vacuum actuator to remove the play.. tight but not too tight...

[erikgundy98]

[Easywind1975]

Guess I'll stay on the same thread for my woes....

I have a 91 automatic with factory Cruise. Did the brake vacuum switch swap to play the odds but it is still inoperable. Today I pulled the cruise module connector and began the Bentley troubleshooting.

Have power to unit, cruise stalk switch tests OK, I get to the brake pedal vacuum switch test and run into issues. The test light does not light as it should (key on, transmission selector in D, brake pedal NOT engaged, test light on pin 3 and grounded).

I trace back to the fuse block and of course Bentley doesn't bother to tell you where the auto relay is, I find it but get thrown off because I don't have a Black/Yellow wire running to it but rather a Blue wire. My Bentley only goes to 89 so I wonder if they switched it up a little, lucky for me someone has a pdf on the interwebs, but the 91 shows the same wire colors.

Now I am not an electrical guru but I'm assuming I should have some juice at this relay in the above circumstances. I'll be back working on it tomorrow night but if anyone has some insight as to where I should start next please advise. I have voltmeter and test light.

Schematic referenced...

Please advise if this is OK to have posted.

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1991 Vanagon GL
2013 Passat
2017 Jetta Sport

[16CVs]

Try by by passing the vacuum line at the pump. Where it Y's off from the pump and goes forward pull that hose and plug it or put a straight nipple in it. Most problems are Vacuum related.
I found on one system that the brake fluid light wire and the Cruise pick up wire use the same type of plug and are about the same length.
I found one of the things that made my cruise reliable was replacing my Clutch switch with a new unit from GW(very well done). This is after I replaced it with a new switch which made it work erratically. I know you have an AT, but I found if I held up the clutch pedal with my foot it would work.
I installed mine from scratch and the diagnosis took more time then the install.
Stacy
_________________
1987 Syncro Westfalia Triple knob (bastard)
1989 Syncro Tristar Triple knob "Swedish"
2013 Jetta Hybrid a true "Zwitter"
Samba member # 14980
Call anytime number 650 722 4914 .
Keep Your van running and upkept tastefully for the love of the hobby.
Don't let your van end up in an "abortions" thread.

[Easywind1975]

I'd be OK bypassing the vacuum portion however the electrical part of the brake pedal switch is inoperable at the moment, so I wouldn't be comfortable without either system working.

Bench test show the switch to be ok and I replaced it with a good used switch as well. I realize there's like 1.5 miles of vacuum line from pump to front that could be corrupt.

Perhaps I could jumper terminal three with a hot feed if I can confirm vacuum cutoff circuit is working. I'd rather just get it all correct, the different wire color to auto relay makes me think that some PO did a repair and now it's up to me to trace their work.

If I get the gist of things when the key is 'on' and the shifter in drive power is fed to relay which feeds voltage to the cruise brain, that voltage makes the brain happy and allows it to do its knee sparing magic. Pressing the brake pedal interrupts this happy voltage as well as the magic vacuum.

I'll tackle some more tonight and report back....
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1991 Vanagon GL
2013 Passat
2017 Jetta Sport

[davevickery]

Pull the hose off the pump that goes to the front. Suck on it and put your tongue over the end. Does it hold vacuum. Pull the tube going to the actuator bulb and do the same thing. It should hold in the sucked in position and the throttle should move.

[Howesight]

I learnt more than I wish I had to in creating my own DIY junkyard CC from the VW parts bin. So here are a few pointers. First, do Dave Vickery's vacuum test.

You can "rebuild" the CC brake pedal switch very easily. Disassemble it. Remove and clean the "o-ring" seal. Place it in ATF or Marvel Mystery Oil and let it soak. Place the remainder of the switch parts in CLR. Agitate every few minutes and the copper traces should then be clean as a whistle after 30 to 60 minutes.

Dry off, place a drop of "3-in-1" oil on the o-ring and the area it bears against and re-assemble. That part is now done.

The stalk switch sometimes goes intermittent, not necessarily testing bad. You can clean the switch by removing it from your steering column and giving the switch part the CLR treatment.

The CC brake pedal switch needs to be properly adjusted to work. You can troubleshoot by jumpering together the two wires that lead to the connector to the switch. This eliminates one of the CC release features, so for safety, be ready to use the stalk switch to cancel CC operation.

Finally, the CC computers do suffer repairable failures on the soldering to the copper traces. If you can borrow a known-good unit to sub in and compare, do so. There are services that rebuild the CC computer if your tests bad.
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'86 Syncro Westy SVX

[Easywind1975]

Thanks guys for the pointers, I'm feeling strongly that brake/vaccum switch is good. Holds vacuum on suck test and continuity changes when pedal depressed. I do not have continuity from the BK/R wire off the relay (this is an automatic) to the computer, I think I should.....

On another note it appears the relay should be energized somehow based on the d+ wire, well I'm only getting a volt or two on that lead which I suspect is not enough to engage the relay. I went back to alternator with key on selector in D and was getting the same voltage, in my mind this should be like 12 volts??? Am I one the right track or do I just suck hard at electrical things?


Lastly when I was doing the Bentley troubleshooting the stalk switch tested fine, however when you test the brake pedal switch you should have a lit light before pressing pedal which should go out once pedal is pressed. The test light never lights up.
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1991 Vanagon GL
2013 Passat
2017 Jetta Sport

[davevickery]

I suck at electrical things too but now if the light is supposed to light up, maybe undo that plug at the vent valve and jumper the plug and see if it now lights up.

[Easywind1975]

Well I'm a little closer I think to working cruise control. I bypassed the A/T relay and brake light switches and rely only on the pedal vacuum switch. The unit feeds the cruise control with voltage with pedal not engaged and breaks the circuit when engaged. Vacuum pump makes noise when jumpered but need to do the vacuum circuit troubleshooting. The vacuum brake switch holds pressure as does the servo, everything else on the bentley troubleshooting checks out so I'm leaning towards a bad or weak vacuum pump or worse case bad computer. In that even I might consider an aftermarket unit.
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1991 Vanagon GL
2013 Passat
2017 Jetta Sport

[davevickery]

I think you can jumper the pump to make sure it has enough power to suck in the actuator bulb. But I doubt that would be the problem it doesn't take much pressure/vacuum. I think when they get weak, the cruise works, but just it is just laggy.

If you got it working with a couple things bipassed, doesn't that give you answer?

I also doubt you need a computer, but I have one I pulled out of 91. I also have some other spare cruise parts.

Dave