Urbanassault

I want to test for signal at the speedometer head but I don't know what to check for. My speedometer regularly does not engage until about 5 minutes of driving. When it does the little red "!" lights for a millisecond and it starts working.
It is pissing me off. <img border="0" alt="[grrrrrrr]" title="" src="graemlins/cussing.gif" />

John Boggiano

Have you tried breaking-and-making the connection on the back of it? It could just be due to a bad contact. I had something similar happen and this was sufficient to fix it.

... for now! <img border="0" title="" alt="[Wink]" src="wink.gif" />

Urbanassault

Yea, I cleaned the contacts, plugged and unplugged several times to no avail.

Adrian

Analogue. In the 1990 model this comes from a pulse sender in the transmission. 1991 and up it is a wheel speed sensor input from the ABS or PDAS/ABS control unit.
Ciao,
Adrian
911C4

JW in Texas

Adrian,
Do you know which pins in the engine compartment box that the speedo wires from the pulse sender on a '90 model plug into. My speedo has been no-op since I did the Supercharged motor swap. I want to run a new harness from the proper pins down to the pulse sensor. Thanks for the help. I really do need to see how fast I am going now <img border="0" title="" alt="[Eek!]" src="eek.gif" />

Adrian

Dear Jay,
The pulse sender feeds to the speedo via plug T30 pins 12 and 14. T30 is supposed to be in the electrical panel in the engine bay on the left.
Ciao,
Adrian
911C4

JW in Texas

Adrian,
Thanks!! What would we do without you! You are once again a life saver. I tried to decode the wiring schematics but my head started to hurt after beating it against the wall to many times
Jay

Mr. C4

Guys,

Does anybody know if the analogue signal, is of 1274, 2548, 5096 or 10192 (pulse/km)?

Which pin it might be on the diagnostic connector? I have alrady been told that the RPM signal is pin no. 14! The reason is because I might install one of these little neat gadgets.

<a href="http://www.defi-shop.com/product/vsd/svsd/svsd_top.htm" target="_blank">http://www.defi-shop.com/product/vsd/svsd/svsd_top.htm</a>

Ciao,

Johannes E.

Urbanassault

Ouch, my parts guy just quoted me 869.00 for a speedo head , can this be for real ?!?

Adrian

Dear Keith,
Yep sound about the high cost of Porsche/VDO instruments. The ! light is the master warn caution. Ths light never comes on without something else comingon. I strongly recommend that you trun the ignition to "ON" but not start and check all the required warn lights illuminate. Try lightly tapping the speedo (I mean lightly as well) to see if the pointer springs up. Does the odometer roll over whilst the pointer does not move. I assume you do not have a trip computer. If you have a trip computer you can check the odometer there as well. You need to establish if you have a speedo problem before spending huge amounts of money. The odometer operation may help in determining this.
Ciao,
Adrian
911C4

Urbanassault

Dear Adrian,
I checked my options listings, no trip computer. It was required that I checked for that particular option due to two different speedo heads. Price with trip computer: $250.00 , Price without trip computer $869.00. All my required lights illuminate when I turn the key on engine off, but I failed to mention that my tail fin light remains on when the speedometer is not operational. Like I said the master warn light flashes once momentarily when the speedo starts to function. I didn't tell you, at that very moment the tail fin light goes off. Yes I tried several times to tap the gauge, "I pulled the gauge out of it's hole and banged it against the steering wheel, is that considered lightly ?" While the gauge is inactive the trip and odometer do not function. Also I have noticed at approximately 70 mph, speedo inop, my tail fin goes up, instead of the usual 45 mph. Tail fin light remains on though. I didn't know speedometers were this complicated.

Adrian

Dear Keith,
The speedo had nothing directly to do with the trip computer. Th edifferenceis the odometer. The speedo for the trip computer systems is cheaper because it has no odometer installed. Mind you that is one expensive odometer.
Failing to mention the rear spoiler warnlight is fairly important. Thw arn light stays on because the signal path for the rear spoiler warn system is broken. The speed signal does not come from the speedo but the tap off is in the speedo and is dependent upon the speedo being powered. From your description you have a speedo problem.
The rear spoiler activation speed is not from the the speedo circuit but from the rh rear wheel speed sensor. I suspect you are upsetting the rear spoiler control unit. Again suggesting that the problem is the speedo.
Ciao,
Adrian
911C4

PS: A light technical tap does not include banging against the steering wheel.