996.1 C4, Cabriolet, Tiptronic - Starting Issue

[Andrew Pudimott]

HI,

 

I previously reported that my starting issue was solved.  It’s not, and now the car won’t start unless the relay is bypassed.  I originally swapped out the starter relay, and same problem came back as evidenced in the video.  

 

I purchased an aftermarket relay and installed it.  That worked for a few days, and then stopped working.  

 

Now, I can only get the car to start if I bypass the relay.  I thought if bypassed the relay, then a replacement relay would be the solution, but that did not work.  Where should I go from here?  

 

 

 

Aftermarket relay below:

 

 

Car starts when the relay is bypassed:

 

 

Where should I go from here?

 

Edited February 23 by Andrew Pudimott

[Andrew Pudimott]

Today, I checked voltage at the battery and also at the post in the engine compartment.  There is no voltage drop noted.  Note, I had just taken the battery off of the charger and measured the voltage in the engine compartment first which will explain the higher voltage coming from the engine compartment.  Yes, the charger was off although still

connected.

 

….And, the car did start again today with the relay bypassed…

Edited February 23 by Andrew Pudimott

[Loren]

When I see cabriolets' with starting problems the first I think of is the immobilizer box under the passenger's seat.

These are prone to flaky operation once they have gotten wet. I would remove it and open it up to see if there is any sign of water damage.

[Andrew Pudimott]

Thanks Loren.   Will do and will report back. 

[Andrew Pudimott]

I checked the immobilizer box, but it was located under the driver’s seat.  Under the passenger seat was just a point of contact for some grounded wires:

 

 

.  

 

I did pull the immobilizer from under the driver’s seat and pulled it apart.  It is perfectly clean:

 

 

I also installed a new ignition switch.  I knew that wasn’t going to help, but I figured I would mention it.  To recap:

 

Car does not start unless I install a jumper wire and bypass the relay.  The battery is charged.  There is no voltage drop between the battery and the post in the engine compartment.  The ignition switch was replaced, but that was totally unnecessary. What’s next?   

Edited yesterday at 02:53 AM by Andrew Pudimott

[Loren]

The immobilizer box looks good. I think you are down to tracing wiring. Look for rodent (chewed marks) or poor grounds due to corrosion.

[Andrew Pudimott]

Sometimes things are just this dumb. Turns out someone had installed what looks like possibly some type of remote starter or something like that?  They tucked the wiring under the dash.  The secondary ground for that was tucked under the dash which caused the intermittent starting issues.  Last week, I found this wiring under the dash and removed it not thinking anything of it:

 

 

Notice the ring terminal that was mostly broken

 

 

Last week I removed this wire almost completely.  It ran from the front of the car to the rear and was spliced in near the relay block.  Turns out it was connected to the ground wire for the starting circuit.  Yellow/purple wire with red stripes

 

 

The genius who spliced into this wire used speaker wire.  I knew last week that something wasn’t right so I left a bunch of that speaker wire behind.  

 

 

 

While going through the diagnostic at the advice of an independent tech, I started thinking that the jumbled up mess of black wiring likely was the culprit.  

 

I confirmed that the relay circuit ground, 85, was the issue by using a multimeter.  I got zero volts on the 85/86 circuit with my wife turning the key.  Big thanks to the tech who guided me on that.  I now have a better understanding on relays.  

 

Once I confirmed the 85/86 circuit was the issue, I figured the speaker wire was likely the ground in that jumbled wiring mess so I twisted the two speaker wire ends together and connected them to a ground

 

 

Car started after this point so I removed the speaker wire and butt connectors then reconnected the ground wire to its original form and put everything back together.  Getting my hands in there with barely any slack was a huge challenge, especially since I didn’t want to pull apart all of the cabrio guts.  

 

Bad news however, the cabrio window cracked from it being so old and cold out.  Special thanks to Loren and the tech (not sure if he wants his name mentioned) who helped me offline.  Now to the cabrio top, but at least the car starts and runs!  

Edited 19 hours ago by Andrew Pudimott