Cruise Control Repairs

[GRS from Kzoo]

I've searched the forum and have seen several items related to cruise control installation and repair but haven't been able to find anything describing my particular problem.

First, the car is a '98 with ~52,000 miles. The cruise stopped functioning more than a year ago. The green light on the dash will not illuminate when I depress the switch at the end of the stalk. The fuse is fine, I have checked it numerous times and even put a new one in despite not finding a problem with the old one.

Other posts seem to have the green light working and I understand that the brake and clutch switches are usually the culprit for that problem. Does anyone have experience with failure at the switch? I figure it could be switch or relay related but without a circuit diagram do not know where to begin.

Thanks,

GRS

[Loren]

The switch pretty much works or it doesn't. Check it with an ohm meter.

[GRS from Kzoo]

The switch pretty much works or it doesn't. Check it with an ohm meter.

Loren,

I tried getting back into this repair today and but I am having trouble figuring how to trace down the wires from the switch without knowing their colors or other way to identify them. I figured I could pull off the cover from the column stalk and get to the wires, but that doesn't seem to want to give up its disassembly secrets easily (and I really don't want to break it).

Any hints on how best to check this out?

GRS

[Loren]

This is about as good as I can get from my schematic...

[GRS from Kzoo]

Thanks, Loren. This detail will make the cruise diagnosis a lot easier, but I do have one more question before I get back into it: To get at the cruise switch in the steering column, do I need to remove the steering wheel or is there a way to remove the upper and lower plastic trim from the steering column without taking off the wheel? (I'm referring to the trim around the column stalks with the rubber inserts around the stalks themselves). There is a small phillips head screw on either side of the column, but removing it did not allow me to easily pull the plastic halves apart.

I had the air bag off today to repair the horn problem (thanks to this forum), but couldn't quite get to the cruise switch as I had hoped, at least without fear of breaking something.

Thanks again for your help (and patience).

GRS

[Loren]

Well, you will have to see what you can see with just the column covers off. There will be limited access.

[Tool Pants]

Not the electrical guy.

Burned out bulb. Switch on the end of the stalk is bad. Something else.

If you want to get to the cruise control connector then remove the steering wheel. Then remove the black plastic plate behind the wheel that has 4 screws. Then remove the left and right screws for the covers. Remove the covers and it is there.

You might ask Richard Hamilton. He worked on a car that had a screwed up switch on the end of the stalk.

Some time ago I had cut off the cruise control stalk from a 3 stalk assembly, for a track car as the guy did not want the cruise control stalk in the way. I had saved the cutoff stalk and ended up giving it to Richard.

Does your car have the OBC/trip computer stalk?

[Richard Hamilton]

My cruise stalk switch problem is a long story, but it wasn't caused by a 'normal' failure. Thanks again to TP for helping me out there!

I would start by checking the braks and clutch switches. The brake switch should be easy - do the brake lights work? You will need to put a meter on the clutch switch to see if you get 12v going on and off on pin 4 (yellow/green wire) as you depress the pedal.

The clutch and brake switches can also slip in their mounting brackets and cause the plunger not to operate the switch.

If it is nothing obvious with these two switches, I would pull the plug on the cruise actuator, and use a multimeter to test that you are getting the expected inputs, as shown on Loren's diagram. It will be easier to check the outputs from the stalk there, as you won't have to remove the steering wheel.

[GRS from Kzoo]

Thanks to all for the input.

I have the three stalk column, Tool Pants. I noticed in a previous string of posts that new column switch assemblies do not have the trim cover on the end of the cruise stalk. It looks like the on-off button in the end of the stalk is simply depressing a switch inside the end of the lever. Does that confirm what you have seen? Maybe I can just pry off the cover from the end of the lever to test the on-off switch?

Richard, the brake lights on my car do work and I will check the clutch switch but I understood these to be the usual problems when the cruise doesn't work despite the indicator light on the dash being illuminated. Since my indicator light doesn't come on when I depress the switch at the end of the stalk lever, I've been assuming that I am not getting power to the system. The fuse is good, so based on the circuit that leaves the switch or the control unit (which I presume is what you call the actuator). From the diagram, it does appear that this is the best place to check it out, but I'm not sure what it looks like or where on the car it is located. Can you direct me to where it is fitted in the car?

Thanks to all,

GRS

[Tool Pants]

You can test the switch on the end of the stalk. I just did it with an ohm meter and an extra 4 stalk switch assembly I have.

With a thin blade you pry on the end of the end of the cover and the cover pops off. You will see a white and black wire going to the switch. The switch is off when it sticks out and on when it is pushed in. I got a closed circuit reading on my meter when I pressed the switch in. The wires are very close together so make sure your meter probes are not touching each other.

The only reason I asked it you had the 4 stalk was in case you had a bad cruise control switch and had to replace the entire assembly. Someone would want an old 4 stalk unit in order to get the OBC stalk for an OBC retrofit.

[Richard Hamilton]

Does the green light come on briefly when you turn on the ignition? It should do. If not, it would be best to check that the actuator/control unit is getting a supply to pin H on the plug. This is my actuator, but bear in mind my car is Right Hand Drive. Excuse the wiring - it was before I got the correct plug when I did the retrofit. I'm sure it would be best to check the voltages at the plug.

[GRS from Kzoo]

I checked and the green light does not come on with the bulb check, but to be honest, I do not recall it ever coming on in the bulb check when the cruise was working. I'm going to look at it again from both the switch and the control unit connector this weekend.

Thanks Tool Pants and Richard!

[Tool Pants]

Here is something on the brake switch.

http://www.pca.org/tech/tech_qa_question.a...7-5EF3E89AA5D4}

[GRS from Kzoo]

OK, I've spent quite a few hours today digging into this (and may be ready to join the circus as a contortionist). No luck thus far getting the cruise to work, but here is what I have found:

1) Clutch switch appears to work fine when checked with a VOM when the connector is off.

2) Although my brake lights work fine (albeit only when the ignition is on) the brake switch appeared to act erratically with a VOM directly on the switch. I'll order a new one on Monday, but figured I would take it apart and see if I could at least determine what was wrong. The contacts were somewhat burned so I disassembled the switch elements, filed them clean and was actually able to get it all back together and seemingly functional with a VOM check. It is a three terminal switch (I think that's a SPST) with a copper terminal between two plated ones. The plated terminals are normally closed and the copper terminal is normally open, at least once I got it all together. I was very hopeful that I resolved the problem (at least for the time) but in a subsequent test drive I still did not get a green cruise control light or any cruise control function.

3) I popped off the cover from the cruise stalk and checked the switch operation directly at its terminals (with the control unit unplugged). The switch works fine! Then, using the diagram and the ohm meter on the control unit terminals, here is what I found for the wiring harness (perhaps this will be a useful reference someday):

CruiseWiring

(Note: I've did this as an Excel spreadsheet and then made an image of it to upload. Hopefully it will view properly, I'll check to see if it does.)

Looking at the diagram and the chart together, much of this seems to make sense. Notice that a lot of the readings to the speed circuit terminal (A) get a resistance reading instead of open or closed. It also shows that when the cruise stalk main switch is closed, this closes the circuit to terminals C (stop light), E (circuit G162 which I'm guessing is the green dash light), F (clutch switch), H (power supply to controller) and J (another stop light switch). It seems reasonable that the main switch would direct power to those functions.

As I said, I will get a new brake switch but since the terminal cleaning had no effect whatsoever I'm not very certain that this will take care of it and am still wondering if the control unit is the problem. Does anyone have any ideas about how to go about checking it (short of buying a new one)? The only thing I haven't done is pulled the dash apart to check the cruise indicator bulb but I can't imagine the failure of the bulb would cause the system not to function. Is that a reasonable assumption?

The saga continues, comments are welcome (and encouraged).

GRS

[GRS from Kzoo]

Maybe this link will view directly on the page:

Cruise Wiring Harness Connectivity

[Richard Hamilton]

Sorry GRS, the spreadsheet just confused me. Maybe it’s just me that can’t interpret it, but what I think you are better checking is that you are getting voltages at the right places, rather than continuity.

Pin H - Supply - should have 12v+ when the ignition is switched on.

Pin D - Set/Acc - should have 12v+ when the ignition is switched on, the cruise switch is depressed on the end of the stalk, and the lever is pushed to set/acc.

Pin B - Off - should have 12v+ when the ignition is switched on, the cruise switch is depressed on the end of the stalk, and drop to 0v when the lever is pulled to off.

Pin G - should have 12v+ when the ignition is switched on, the cruise switch is depressed on the end of the stalk, and the lever is lowered to resume.

Pin F - Clutch Switch - should have 12v+ when the ignition is switched on and drop to 0v the clutch is depressed.

Pin A - Speed Signal - I think this is a pulse which will vary with speed, and would be difficult to test. If your other speed-related devices (spoiler etc) are working, I would assume this to be OK.

Pin C - Stop Light Switch - should have 12v+ when the brake pedal is pressed.

Pin J - Stop Light Switch - should have 12v+ when the brake pedal is up.

Pin K - Signal out to the Diagnostic Socket & Cluster Light – the control module should give a 12v+ signal out when the ignition is switched on and the cruise switch is depressed on the end of the stalk. It should also have 12v+ for a few seconds when the ignition is switched on with the cruise switch off. The conecctor would have to be plugged in to test this.

Pin E - Ground

HTH.

EDIT: Outputs to pin B and pin F corrected - see later posts - amendments are underlined

Edited July 15, 2007 by Richard Hamilton

[GRS from Kzoo]

Thank you, Richard! This looks to be exactly what I need to thoroughly check it out.

It may need to wait until next weekend before I can dig back into it, but I'll let you know how it goes.

GRS

[Tool Pants]

I spoke to a mechanic briefly and hope I understood what he said.

He said the cruise control will work even with a burned out indicator bulb. If the brake switch is bad the indicator light will still go on but you cannot set a speed.

He said the most common problem is a bad switch on the end of the stalk, but I told him you ruled that out. Next is the control unit.

Might be a silly question, but how do you know the cruise control is not working aside from the fact the green light does not come on?

[GRS from Kzoo]

There is absolutely no cruise function insofar as setting or holding speed. I hoped that the non-functional light might have been a helpful clue for diagnosing the problem. If the switch on the end of the stalk were defective, I don't think the light would illuminate since it used to go on when the switch was depressed. From the circuit, it does appear that there could be other switch issues that would not have showed up by measuring continuity directly at the stalk switch as pins D and B both depend on the switch for power. I still haven't figured out where the cruise lamp gets its power from but it may get illuminated through the diagnostic pin K.

With Richard's detailed Input/output list below, I should be able to verify whether any other of the switch functions beside on/off are at fault. If it checks out completely, the only thing left will be the controller.

Thanks again for the insights.

[Richard Hamilton]

The green cluster light gets its feed from Pin K on the cruise module plug. This wire is also connected to pin 8 of the diagnostic socket, so you should be able to measure 12v+ at that connector with the ignition on, and the cruise switch depressed.

Cruise Module:

OBD2 Socket:

Edited July 11, 2007 by Richard Hamilton

[GRS from Kzoo]

OK, checking out the voltages between pin E and the others, here's what I get:

Pin H – Supply – should have 12v+ when the ignition is switched on.

YES!

Pin D – Set/Acc – should have 12v+ when the ignition is switched on, the cruise switch is depressed on the end of the stalk, and the lever is pushed to set/acc.

YES!

Pin B – Off - should have 12v+ when the ignition is switched on, the cruise switch is depressed on the end of the stalk, and the lever is pulled to off.

I have just the opposite, pin B gives 12v with ignition on but goes to 0 when I pull the lever to off.

Pin G - should have 12v+ when the ignition is switched on, the cruise switch is depressed on the end of the stalk, and the lever is lowered to resume.

YES!

Pin F – Clutch Switch - should have 12v+ when the ignition is switched on and the clutch is depressed.

Again, I have the opposite, it is 12v with the ignition on and the clutch up and 0v when the clutch is depressed.

Pin A – Speed Signal – I think this is a pulse which will vary with speed, and would be difficult to test. If your other speed-related devices (spoiler etc) are working, I would assume this to be OK.

I did not check anything on this.

Pin C – Stop Light Switch - should have 12v+ when the brake pedal is pressed.

Very interesting, here I only get 11.58v, which is .6 less than the others. I'm pretty certain this is due to the brake switch situation where the normally closed terminals work reliably but the normally open terminals act a bit flaky.

Pin J – Stop Light Switch - should have 12v+ when the brake pedal is up.

YES!

Pin K – Signal out to the Diagnostic Socket & Cluster Light – the control module should give a 12v+ signal out when the ignition is switched on and the cruise switch is depressed on the end of the stalk. It should also have 12v+ for a few seconds when the ignition is switched on with the cruise switch off. The connector would have to be plugged in to test this.

I get 0 volts here, but did not try momentary on with ignition. I do not get the light to go on with a normal start bulb check.

I also checked terminal 8 of the dignostic plug and do not get power on that pin either.

So I think I have confirmed that the stalk switches all work. The reversal of function on pins B and F is interesting. Richard, can you confirm how they work on yours? I checked mine many times and figure if the logic is reversed it either means that the logic changed in the controller with a model year or my controller has problems. Does anybody have a lead on replacement controllers?

I still plan to replace the brake switch but did not find one this week due to a little confusion over part numbers. According to the dealers, the switch listed for my '98 is supposed to be PN 996.613.114.01 but it apparently has 4 terminals, not 3 like the one in mine. I looked at my switch today and confirmed it is a 996.613.110.01, which appears on the list as the '97 model part. The connector for mine looks like it would work with the 4 pin version since it has a space without a terminal in the 4th position. Has anybody out there replaced a 3 terminal switch with a 4?

As always, I look forward to your analysis.

Thanks,

GRS

[Richard Hamilton]

GRS

Those outputs were from my first interpretaion of the schematic.

Pin B - maybe I interpreted the schematic wrong - I obviously got D and G right (the other two outputs from the stalk), but it seems that B may be the opposite sense. Looking at it again, I can see that the switch must be normally closed, so you are getting the correct output.

Pin F - I have a Tiptronic, so I can't check the clutch switch. To me, the schematic shows the clutch switch normally open, but I guess it must be normally closed. Therefore I think this must be correct on your car.

The brake switch only has 3 terminals connected, but they are numbered 1, 2, and 4 - so that's where the confusion probably lies.

It seems to me that the problem is with your control unit, and the lack of output from pin K might confirm that. It might be worth taking it out, opening it up, and checking for an obvious fault inside. From memory, the circuit board connects to the socket with an edge connector, so it might be worth checking that the pins are clean. Otherwise, maybe you could get a used unit from a dismantler - that's where I got one from for my retrofit.

Edited July 15, 2007 by Richard Hamilton

[GRS from Kzoo]

OK, I finally have more to report!

I replaced the brake switch a couple of weeks ago, and it made no difference (but then again I don't think any of us expected it to). BTW, the four terminal switch appears to have replaced the three terminal version which was originally in my car and is what I installed.

Today I was finally able to locate a control unit from a dismantler ($200), which motivated me to get the old one out and look at it. Not so easy to get out, but if it helps somebody in the future, here's the steps I took:

1) Remove the duct that runs transversely from the HVAC unit to the left side of the footwell.

2) Remove the visible screw in the remaining duct to the HVAC and pull it aside to observe the controller.

3) There are three 10 mm bolts holding the control unit to key-slotted holes in the brake pedal bracket. Loosen the top two 1/2 turn or less and leave them in place. (These are the harder two to access). Remove the third bolt entirely. I found that I could not remove the unit with this bolt in place as it made it too difficult to get sufficient clearance to pull out the controller.

4) Pull the entire controller (still attached to the throttle pedal) down.

5) The electronic control unit is held to the controller by four phillips head screws at its corners.

Of course, the part number on my unit (996-617-021-04) is not the same as the one the dismantler has (996-618-051-02). First question: Does anyone out there know if the dismantler's part will work on my '98?

In looking my unit over closely I did find one transistor which appears to have a weak solder joint at its connection to the top of the board, although the corresponding joint at the bottom of the board looks fine. I'm no EE, but it seems like that may be an issue, especially since there do not appear to be any traces to that lead on the bottom. Hopefully, I can get someone who knows to look at it.

Any thoughts?

Thanks again for all of the help so far.

GRS

[Richard Hamilton]

996-618-051-02 does not seem to be a valid number. If I were you I wouldn't risk it - try and find one with the matching part number.

Just looked at the Price Search here - That number seems to be for a "Litronic Control Uni", priced at $0.03!!

Edited July 31, 2007 by Richard Hamilton

[GRS from Kzoo]

Just an update...

After resoldering a few questionable solder joints and still not getting any voltage out of pin "K", I've shipped off the ECU to Auto & Truck Electronics in West Palm Beach, Florida for rebuild (www.autoecu.com). They rebuild all sorts of automotive controllers and gave me a price of $229 to do the job, which includes a 1 year warranty. Best I was able to find for used ECUs is $250-300.

I'll let you know how it works out.

GRS