43bullet

84 911.

speedo and odo not working. there was a blown fuse in the circuit. #4. replaced that - rest of instruments work on that circuit. Ive replaced the impulse sensor. no luck. only thing left is speedo, correct?

thanks

Dan

Drisump

I would pull the speedo if you haven't already, perhaps it's simply a loose connection. Speedo is a simple removal, it's only held in place by a rubber seal. Care must be exercised to not mark the material that surrounds the gauge when prying on the bezel. Cheers

stealthboy

Avoid the temptation to pry it out with a screwdriver - get a set of trim removal tools.

I had to take mine out and ended up sending it off for repair because the speedo and odo were not working.

theiceman

isn't there a common plastic gear inside these that break ? or is that for the odo only ?

43bullet

so my current thought it is either the speedo itself (gears) or electrical connection on the back of the speedo. will check and post up results of my next steps. the odd thing is, that something happened that blew the fuse to the circuit, and now that it has been replaced, the circuit works (fuse not blown), but speedo isn't working. so, im assuming its the speedo itself causing the problem, now that the impulse sender is switched out.

Dan

Drisump

The odometer/tripomter is driven by nylon gears that commonly fail in our cars. Both of my 911's have had these gears go. The first I sent to North Hollywood and second I did myself. This results in working speedometer but no action on the od/trip. The OP has a circumstance where neither is working. IMHO there is either a lack of power to the speedo, bad ground, or the speedo itself is faulty.....and yes plastic trim tools work great in the removal process. Personally first I would pull the speedo but leave connected and examine the electrical connectors before pulling it out of the car completely. Cheers

oldskewel

Yes. When the gear fails, the speedo will still work but the odo will not.

BTW, that gear, based on the price, is built from the most expensive plastic known to man. I remember reading that the widespread failures of these gears was caused because when the speedo's were originally manufactured, the gears were greased with grease that happened to cause the plastic to disintegrate after 20 years or so. That's what happened to mine. The teeth were almost all gone, while there was very little wear on the worm gear, etc.

Mondrian

Could the magnetic sensor cause double failure? If so might be worth checking a loose connector as that might have triped the fuse.

theiceman

Yes I think he started out by changing that. Did not resolve the issue so sounds like speedo is fried

berk

I have the same problem i plan on troubleshooting this weekend. I will report back if i can fix it quickly

JCP911S

Quick fix... unplug the speedo, and PRESTO!... you have a low mile 911 that will appreciate in value....

The tach will actually give you a more accurate measure of your speed... thats why they put it in the middle of the instrument display.

Cheers