'91 Jetta cruise control question

Have a diesel with cruise that has not been working, so did the diagnosis procedure listed in the Bentley manual. The procedure is fairly simple, using a jumper wire and indicator light. The cruise control/turn signal switch handle and and vacuum pump work fine. When checking the functioning of the small indicators that mount on the clutch and brake pedals, the power seems to be backwards. If I read the manual correctly, I connect a lead, with the indicator light, between the #1 and #3 positions on the cruise control's brain. With the key ON and the cruise ON, when I step on the brake or clutch, the light is supposed to turn on. My problem is that the light is ON when I first hook up to the #1 and #3 positions, and goes OUT when I step on either of the pedals. Have I somehow made some power connections backwards? Thanks for any help you folks may provide.

Reply to
jettaman8691
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What you see is normal. When not touching either pedal, there should be continuity from terminal 3 to ground. Thus a test light between terminal

3 and terminal 1 (positive supply) should light up with no pedals pressed and turn off when touching either pedal.

On some A2 cars, terminal 3 was connected to the brake switch, the other side of the brake switch was connected to the clutch switch, and finally the other side of the clutch switch was connected to ground. On others the clutch switch was connected to the brake lights switch instead of ground. In this configuration the ground circuit is completed through the brake light filaments (thus if all brake light bulbs were out the cruise wouldn't work). I don't think this is relevant for your problem, I mention it because it could potentially cause confusion when troubleshooting.

The next test to do (not sure if it is mentioned in Bentley or not) is to hook a voltmeter (don't use a test light) between terminal 5 (speed sensor) and ground (e.g. from terminal 8) at the harness that plugs in to the brain. Then drive really slowly across a parking lot (sloooow walking pace only). It doesn't matter if the cruise main switch is on or off and it doesn't matter if the brain is plugged in or not. The voltage should alternate between around 0 volts and some higher voltage (5 volts or 10 volts, I can't remember). If the voltage is not alternating, the speed sensor is probably bad. It is mounted to the back of the speedometer in the instrument cluster. Small Hall-effect sender in a plastic holder, mounted with two screws. The flex circuit from the instrument cluster connects to it. I believe there were two different kinds in use depending on whether the car has the MFA or not.

Both the speed sensor and the cruise brain are pretty easy to find at the junk yard. The VW part number is printed on the housing, and the unit was used in a wide variety of both Audis and VW's for years and years. I picked up a *complete* cruise control system for my '87 for under $50 at a local junk yard.

Reply to
Randolph

Again, thank you. I did finally check the resistance of the speed sensor and found that it was bad. Put in a different one I pulled from a spare speedo and now the cruise works fine.

Reply to
jettaman8691

I read Randolf's troubleshooting procedure with great interest. The cruise control in my '95 has drifted from intermittent to engage to hardly ever engaging. Once engaged it worked well. Re-engaging after tapping the brake for traffic was also intermittent.

My (C)1996 Bentley does not have a troubleshooting procedure-- at least as far as I can find.

I have pulled off the knee bar, sill trim and relay/fuse cover panel. Accessibility was not quite what I had hoped for.

The control module is said to be in the A pillar. To me that means windshield-high. Yet it looks like the area behind the lower trim where the hood release mounts would have more room. Could somebody confirm that the module is indeed up high. Removing the trim either place seems to be non-trivial. And if I do get in there would I probably be able to access a connector to use Randolf's procedure?

Reply to
Tom's VR6

I see a silver-colored module in the dash near the headlight switch. It says Steuergerät 5GA 004 397-11.

The far side of the box (nearer to firewall) has a black connector.

Is this the cruise control module, or the alarm module?

Reply to
Tom's VR6

5GA 004 397-11 is the manufacturer's (Hella) part number, the full description is "GR Steuergerat 12V" and it is indeed the cruise control brain.

From my copy of ETKA it seems the internal VW part number is 1H0 907

305. On my '87 the module had both the VW part number and the manufacturer's part number printed on the box.
Reply to
Randolph

Yeah the silver one is the cc the black (or white) one is the alarm I have had this problem happend on two a3's the cruise computer i dead / on the way out. I put a used one in and all was back t norm

Da

In rec.autos.makers.vw.watercooled, Tom's VR6 wrote

I see a silver-colored module in the dash near the headlight switch It says Steuergerät 5GA 004 397-11

The far side of the box (nearer to firewall) has a black connector

Is this the cruise control module, or the alar

module?[/quote:463d708ab3 From VWsport.com NNTP Gateway

Reply to
admin

Thanks! I can proceed to trying to access the connector and troubleshooting.

Reply to
Tom's VR6

Thanks!

Reports tend to indicate they are more trouble-prone than most electronic things. However since mine failed more progressively, I wonder if it would be less likely an electronic problem.

Reply to
Tom's VR6

Reply to
Joe Hancock

I was excited to find the clutch switch to be a little flaky. Wiggling the clutch cable made the voltage change in the test at the module connector.

Woohoo! I was going to be the rare one who did not end up with a bad module.

I took the switch off and apart. I cleaned the contacts with good contact cleaner without removing the vacuum grease. I re-assembled and tested. Looked good on the ohmmeter. I re-installed with some difficulty.

Unfortunately in my test drive cruise control still did not engage.

I removed and pried into the module. No visible problem. I connected it un-sheathed. The only test I did that way to confirm the electronics had +5 volt Vcc. Dang. I was hoping it was the regulator.

There is the 5-volt regulator in a heat-sunk TO-220, a transistor in TO-220 package, about 6 TO-92 transistors, a 40-pin DIP 80C49 microcontroller, two CMOS 14-pin DIP gate ICs, a relay, and a bunch of other components.

Reply to
Tom's VR6

Did you check the "Set" switch? The stalk I installed (taken from an '86 Jetta at the wreckers) is a little flaky, takes fairly firm press on the set button to get the cruise to engage. Same thing with the switch at the end of the MFA stalk, when I got the car (an '87, bought used in '95) that switch was very hard to operate, but has gotten better over the years. Same type switch as the cruise set switch (at least on my '86 / '87 hybrid)

Test>

Reply to
Randolph

Hi Guys,

I have a similar problem on my Ford Galaxy, uses the same Hella/VW part. Mine has R1 in and exploded state and I can't read the resistor value because of this. R1 was under a blob of white silicone rubber near the connector plug.

Is anyone able to supply me with the value of this resistor please?

Cheers

Snooper601

Reply to
Snooper601

Chris,

R1=10 Om. I just cleaned up the white blub to see if mine R1 is blown too. It was fine though, and measured 10 Oms.

Reply to
VladC

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