humbucker

The speedometer on my 86 turbo just quit working.I have tried changing the impulse sensor,yesterday I took the gauge cluster out to change bulbs and replace reflective surace,and also checked gears on speedo.

The gears looked fine and I could get odometer to turn by moving the worm gear.I cleaned the grounds and checked the fuses,which all seem to be ok.

What should I try next?I have a pinion gear for the trans.does the output shaft have to come out to put it in?

Any suggetions would be appreciated.Thanks

944Ross

Just unscrew the aluminum holder for the pinion, under the sender, and take it straight off. I don't think you could drop the pinion into the trans, but do you really want to find out?! Be careful!

humbucker

Thanks 944 Ross,I will check it out.

humbucker

Well I checked the pinion on the output shaft,and it looks fine.
Has anybody here had a speedometer motor go out.

What would be the best way to check it?Could I give it some DC voltage directly to see if its good?thnx

944Ross

Check for 12v (+) on the pin at the sender connector with the key on. It's a nasty, dirty area, could be corroded or broken connection. Should be Pin 1 if I'm reading the schematic right. Pin 2 should be ground, it could also be bad.

humbucker

Thanks,944 Ross.

If I have 12v at the plug to the sensor does that mean the speedometer motor on the back of the speedo is ok?

944Ross

No, it just means there is power to the sender. The sender converts that to pulses that go to the speedo. You need to figure out if the problem is the sender, power, or the speedo. This test gives you one piece of info.

humbucker

I replaced the impulse sensor,and I think I checked the plug and it had power.
Do you know if I check the other two conections on the plug (one at a time )if they should ground to the body?
If the plug checks out, I guess I'll pull the instrument cluster out and check the speedo motor to see if its shorted out.

944Ross

I'd be careful poking around, there are electronics inside the sender. Basically there is a magnet that spins around, a reed switch that closes when the magnet is near, but it looked to me like there is a chip that conditions the signal. This is from the schematic.

humbucker

Thanks I'll just check that the plug is getting power.If it is ,I guess I'll pull the instrument cluster to see if I missed something on there,and check the speedo motor to see if its fried.