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OBC retrofit, ignition switch = cruise control doesn't work

tmc
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tmc Member

tmc

Posted
Posted

Got a head scratcher here...

My local shop replaced the ignition switch on my 99 996 C2. I didn't use the cruise control after they did that.

A couple of days later, I did the OBC retrofit (yesterday).

The cruise control doesn't work (although everything else is fine).

I took things apart, traced things, etc, and can't figure out what's going on.

Is there a chance the ignition switch swap broke the cruise control somehow? (Any other theories?)

tmc

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Loren Member

Loren

Posted
  • Admin
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Cruise control was stanadard on US 996's. It looks like you may need to recheck your wiring.

BTW... did you have someone turn on OBC in your cluster?

tmc Member

tmc

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  • Author
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I rechecked (twice).

The OBC works and yeah, I had someone turn it on before I did the retrofit.

Do you know if the cruise control goes through the cluster, and if so, is it through the same (white) connector, or through the blue or black one?

It seems the key wire out of the four-wire cruise control connector is the brown-yellow wire, but I don't see where else that goes.

thanks

tmc

tmc Member

tmc

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Thanks Loren!

Do you know where the cruise control unit is located physically?

Maybe I bumped a lead off when I did my OBC hack.

tmc

tmc Member

tmc

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  • Author
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Did you plug in the connector to the cruise control stalk?

:D Yeah I did that, or at least I think we're talking about the same thing. There's a small four-wire connector that comes off of the stalk assembly. Wires out of that connector were, if I recall, a brown/yellow wire, a yellow wire, a blue wire and a black wire. The black was the only one I could trace with my ohm meter (it's ground....)

tmc Member

tmc

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  • Author
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Uh... black is power - brown is ground.

Not sure how I could get that reversed, but anyway, I didn't mess with either the female or male side of the connector.

Guess I'll either live w/o cruise or take it to a dealer :(

tmc Member

tmc

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When you push the switch at the end of the cruise control stalk does the green indicator light in the instrument cluster come on?

No it doesn't.

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Tool Pants Member

Tool Pants

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I would normally say to make sure the cruise control conntector is plugged in, but you say you checked.

Next would be the switch on the end of the stalk. I think Richard Hamilton can tell you how to check the switch.

Check to see that all the wires on the clutch pedal switches are connected.

The only other thing I can suggest is to put your old 3 stalk/switch assembly back in and see if it works.

tmc Member

tmc

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  • Author
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I would normally say to make sure the cruise control conntector is plugged in, but you say you checked.

Next would be the switch on the end of the stalk. I think Richard Hamilton can tell you how to check the switch.

Check to see that all the wires on the clutch pedal switches are connected.

The only other thing I can suggest is to put your old 3 stalk/switch assembly back in and see if it works.

Hi Tool Pants,

I tried the swap of putting the 3-stalk back in and the same behavior results: no cruise, no light in the cluster when I press the switch, nada.

Where is the clutch pedal switch?

Thanks

tmc

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Tool Pants Member

Tool Pants

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Look under the dash at the clutch pedal. There are 2 switches. The starter interlock and cruise control switches, but I think it has something to do with the OBC retrofit since you ruled out the cruise control stalk.

I can't see how a replacement ignition switch would cause the problem, but I'm not the electrical guy.

Maybe the indicator bulb was going bad and burned out when you pulled the instrument cluster. I would check that bulb, but you have to pull the cluster again, and open it up. I have a feeling the cruise control will not work if the bulb is bad.

Also, do your brake lights work?

If all else fails, you can always try a brick on the gas pedal....

Richard Hamilton Member

Richard Hamilton

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Sorry, been on holiday and just got back.

I know it sounds obvious, but have you checked fuse B7? That's the power supply for the cruise. Also, chech that the 4-way connector is in the right way round - it is polarised, but not very well.

tmc Member

tmc

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  • Author
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Sorry, been on holiday and just got back.

I know it sounds obvious, but have you checked fuse B7? That's the power supply for the cruise. Also, chech that the 4-way connector is in the right way round - it is polarised, but not very well.

B7 is good.

By 4-way connector, you mean the one that attaches to the stalk? It's the right way.

What does the other end connect to? Loren's diagram showed it connecting to the "CONTROL UNIT CRUISE CONTROL". Where is that located in the car? Maybe I accidentally disconnected that.

Thanks!

Richard Hamilton Member

Richard Hamilton

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Yes, I meant the small 4-way connector that connects the stalk to the loom.

The actuator looks like this:

post-4000-1161084483_thumb.jpg

Bear in mind that this is for a RHD car so has an additional mounting bracket.

In a RHD car it fits like this:

post-4000-1161084513_thumb.jpg

The wiring is temporary in this photo, you should have a plug on the end which looks like this:

post-4000-1161084533_thumb.jpg

Here's a simplified wiring diagram:

post-4000-1161085102_thumb.jpg

It would be a hard job to disturb the plug connection. Other than that, I can only suggest checking all the other connections. I'm not sure if the PST2 will show the input signals on the cruise control module - maybe Loren could comment here.

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Loren Member

Loren

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With a PST2 you can test the cruise control lever/button actuation (i.e. store/accelerate and decelerate/resume). These can be viewed using the Input Signals part of the Instrument Cluster section.

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Loren Member

Loren

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Richard - my mistake you only get those on the newer cruise control when it is part of the DME.

So, no PST2 tests that I can find for the older version.

Richard Hamilton Member

Richard Hamilton

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Going back to tmc's problem, have you checked that the brake lights work (as suggested by Tool Pants)? Also, the cruise will not engage if the clutch cruise switch is operated. If it is secured the same way as the brake switch, then it can slip in the mounting bracket and cause the switch not to operate.

Another thought - and this is a long shot - are we sure your car is not eGas? I suppose if it was a very late build in 1999 it might be DME7.2 and we are all barking up the wrong tree. Check your option sticker for (M)620 - if it has then you have egas, and there is no mechanical actuator.

Richard Hamilton Member

Richard Hamilton

Posted
Posted
Richard - my mistake you only get those on the newer cruise control when it is part of the DME.

So, no PST2 tests that I can find for the older version.

That's a relief! I have used the Input signals for eGas cars, and it is a very useful test - especially when you get wires the wrong way around!! There is a wire from the cruise actuator to the diagnostic plug on early cars, but I have no idea what it could be for.

Richard Hamilton Member

Richard Hamilton

Posted
Posted

I have a wiring diagram which shows DME7.2 on a sheet labelled "Carrera (996) Sheet 18 Model 99/00" - I was thinking that maybe some 99 C2's might be 7.2, but maybe the sheet is intended for the 1999 C4.

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