Cruise Control Repairs

[GRS from Kzoo]

Well, after testing the part, Auto and Truck Electronics tells me that the unit is not repairable as the eprom is shot and they cannot replace that (probably because they do not have the software to put in it). Looks like I need to find a new unit.

Leads me to wonder what would have caused the eprom to go. The only thing I can figure is an electrical glitch in the power supply to it. I did need to replace the ignition switch as I had erratic operability of things like the HVAC fan. Since I was in the habit of leaving the cruise stalk "on" switch in the on position, do you think the ignition switch issue could have led to the failure of the cruise control ECU? Once it's fixed I'll be sure to keep it off when not in use.

Thanks to all on this board for your help. I've learned a lot and at least I feel certain that I've got to the root cause of the problem.

GRS

[GRS from Kzoo]

Well, I received a used cruise control module from a recycler in Wisconsin, installed it, and the cruise on my car still doesn't work. Same symptoms as before, no green light, no functions (and I put about 800 miles on the car this weekend for a thorough test).

Before removing it, I again checked out the pins on the harness connector and everything is still as it was before (per my post on July 14), even to the point where Pin C has less than 12 volts (although this time it was 11.63 and the brake switch had been replaced with a new one). The module was guaranteed so I will pack it up and get a refund, but this does have me wondering what I may have missed. Power, ground and all switch functions (both for the stalk and pedals) all check out OK.

I have a few other used modules lined up to try but this has me quite baffled and thinking I must have missed something. Any other suggestions out there?

Thanks,

GRS

[00BoxsterS]

Did you ever resolve this?

From Tool Pants' response above, he spoke with a mechanic that said the CC should work with the indicator bulb burned out. My CC was inop for over a year and I replaced the clutch switch with no improvement. My mechanic scanned it and said the indicator bulb was out so I replaced it and now it works!

Now I'm curious, is the bulb part of the circuit, or could it be coincidence and I did something else during the bulb replacement?

[GRS from Kzoo]

No I haven't but you've giving me sufficient motivation to replace the bulb as soon as I can use my hand again. (I had surgery on my right hand to repair my thumb after an injury and this will take a couple months to heal).

Thanks 00BoxsterS!

[00BoxsterS]

Replacing the bulb was a 10 minute job. Bulb was a Porsche only bulb. $3.65 at the dealer. The hardest part was removing and replacing the bolt behind the screen mesh thing. I used the baggie method.

Jon

[GRS from Kzoo]

I'm anxious to get to this as soon as I have the use of two hands again. I'm presuming you are referring to the instrument cluster removal at http://boxsters.addr.com/hacks/cluster.htm and that the mesh thing is the grill to the left of the speedometer. Can you describe the baggie method? I've had the cluster off before to replace lights in the IP but never needed to use a baggie for anything.

GRS

[GRS from Kzoo]

Jon,

One more thing...

Do you happen to have the part number for the bulb? I see three different bulb numbers for the cluster!

GRS

[GRS from Kzoo]

I can finally report success and unequivocally state that a dead light bulb in the instrument panel will render the cruise control inoperative on a 1998 Boxster!

After 5 years, many hours and hundreds of dollars it is all working again. I am thrilled but feel like a fool since I have actually had a spare light bulb in my ash tray the entire time.

Thanks once again to everybody here.

[coleta]

The only one that should feel like a fool is the knucklehead that engineered this. Good show. You gave it to the man. I'm happy for you.Congratulations.

[dghii]

Wow! As a working electronic engineer, I want to apologize to you on behalf of my dumbaz brethren at the factory. What an embarrassing design!

[topradio]

Just read this through as I did a retrofit cruise to my 98 box recently and it works great.

What would worry me is the response of the guys that wanted circa $300 to service your old unit and then condemed it!!!:cursing:

[GRS from Kzoo]

I had pretty well forgotten about that! I think there's a lesson for all of you out there that you'll want to think twice about doing any business with the firm named in my post of August 10, 2007. Their claim that my unit checked out bad is very suspicious, especially since they now seem to have one listed for sale at $289 + $15 shipping. Looks like they have changed their name but the link in that earlier post will take you to their site. They did not charge me for their "analysis" but by telling me the eprom was fried they got me to let them keep it to avoid paying $100 for their effort. Very suspicious!

[wvicary]

They are several manufactures that use the indicator light operate the cruise control, it is one of the first things that should be verified. Glad you got it sorted.

[mckinlay]

I resurrected this post as it saved me hours of time and lots of money.  As Loren has been known to post "Search is your friend".  I noticed one day that my cruise control would not turn on.  I was preparing to check and or bypass the brake and clutch switches as well as the switch in the stalk.  I had priced a new cruise control module (ouch!).  However, after searching, I came across this post.  I went back to the car and noted that the cruise control light did not come on when starting the car.  I did confirm the fuse was OK.  I ordered a new bulb (less than $5).  Pulling the Instrument Cluster was very easy.  I pulled the bulb and tested it with a VOM.  It was dead.  I replaced the bulb and put it all back together.  Cruise Control works fine.  It took me about an hour start to finish.  I took it slow because I had never done this before.  If I did it again, maybe 15 -20 minutes max,?  Search was indeed my friend.

[Loren]

I resurrected this post as it saved me hours of time and lots of money.  As Loren has been known to post "Search is your friend".  I noticed one day that my cruise control would not turn on.  I was preparing to check and or bypass the brake and clutch switches as well as the switch in the stalk.  I had priced a new cruise control module (ouch!).  However, after searching, I came across this post.  I went back to the car and noted that the cruise control light did not come on when starting the car.  I did confirm the fuse was OK.  I ordered a new bulb (less than $5).  Pulling the Instrument Cluster was very easy.  I pulled the bulb and tested it with a VOM.  It was dead.  I replaced the bulb and put it all back together.  Cruise Control works fine.  It took me about an hour start to finish.  I took it slow because I had never done this before.  If I did it again, maybe 15 -20 minutes max,?  Search was indeed my friend.

 

:thumbup:

[GRS from Kzoo]

McKinlay, I'm glad to see, even after all these years, that the all the posting saved somebody a lot of headaches (as well as backaches crawling under the instrument panel). 

 

I actually still think about the silly way Porsche engineered the cruise control circuit almost every time I'm out driving my car.