Speedometer Problems

[Number1_dog]

1979 SC
Speedometer ran when I first got car, then had the transmission re-built (by Gary Fairbanks in CT) and two years rebuilding the engine etc... and it now doesn't work.

I got a new sensor, and just had my speedo re-built by North Hollywood.
I have continuity from sensor H wireattachment to the two brown wires at back of speedo.
4 wires attach to the back of speedo
1) have power on red/black when ignition switch turned on and attached to +

speedometer contact A is left empty

2) the green sensor wire goes to 31b and
wires 3, the other sensor wire and wire 4, a ground wire, goes to the - .

Could the transmission be missing whatever the sensor picks up?
Can I check the sensor ? Should there be continuity between the two sensor wires?

please help!!!!!

dog

[Number1_dog]

Anyone???

[Kidasters]

Here are my guesses:

1) Your sending unit is dead, or installed backwards. It happens.

2) When NHS re-did your speedo, they put it together wrong, and the needle is stuck. I need to send my speedo back to them, since the needle sticks under 20 mph.

I can't remember how you check the sensor. It's a magnetic switch. I thought I remembered a thread where you could remove it and clean underneath it? Can't remember.

Finally - are you sure you have it wired right? NHS sent me a nice little diagram when they re-did my speedo. If I can find it, I'll post it.

[Targalid]

Just a thought. If this were my car, I would pull the speedometer and connect the input wires to a voltmeter to see if a voltage is generated when the car is moved. A helper could watch the meter while you are driving or vice versa. My guess is there is a disconnect between the sender and your speedo. This would be a way to check it. North Hollywood Speedo has a great reputation so I think the problem is with the car rather than with their repair. If you have a friend with a similar model you could swap speedos to test for function that way.

[86 911 Targa]

Originally Posted by Number1_dog

1979 SC
Speedometer ran when I first got car, then had the transmission re-built (by Gary Fairbanks in CT) and two years rebuilding the engine etc... and it now doesn't work.

I got a new sensor, and just had my speedo re-built by North Hollywood.
I have continuity from sensor H wireattachment to the two brown wires at back of speedo.
4 wires attach to the back of speedo
1) have power on red/black when ignition switch turned on and attached to +

speedometer contact A is left empty

2) the green sensor wire goes to 31b and
wires 3, the other sensor wire and wire 4, a ground wire, goes to the - .

Could the transmission be missing whatever the sensor picks up?
Can I check the sensor ? Should there be continuity between the two sensor wires?


please help!!!!!

dog

Hint: Chip damage prevention.

[schumicat]

the sender wiring connects under the panel in the rear floor. see if those wires are connected. the speedometer can be tested by unplugging and rapidly touching the 2 wires from the speedometer together. that should make the speedo needle move. the sender attaches to a recess on the trans on the passenger side and is held on with a small bolt. correctly installed a rough surface faces out. if a smooth plastic surface faces out is it installed wrong.

[Roger Shultz]

To verify the operation of the sensor you must use an ohm meter instead of a voltmeter. If the sensor magnetic switch is working properly with an ohm meter across the two wires which you can access in the tunnel, you should see the resistance reading go from zero (a short) to infinity as the wheels are turned. You can jack the car up in the rear and do this or simply move the car while a helper looks at the meter to see what it is doing.

If that open and shorting action does not occur, then you will know in which direction the problem is occurring.

[Number1_dog]

Thanks Rodger, this is what I was looking for!

[cellison]

related to my 79:

a few weeks ago, the odometer on my 79 stopped working but the speedo worked fine. i popped the speedo out and took it to a shop in the area who other pelicans have used for repairs. he was familiar with the problem...replaced the broken gear and recailbrated it. yesterday i popped it back in the car and went for a drive. I got up to about 15-20 MPH (estimated) in the neighborhood, but the speedo and odo were not working and went back home. i relooked at the wiring and it was how i pulled it, but went ahead and swapped the 2 brown wires in case i wrote it down wrong when i poped it out. I still did not work, and rewired to as it as before (in the distorted picture). i figured this would be plug and play since i didn't do anything else in the transmission/sensor and i assumed the speedo is still getting a signal. Any thing I should look at? which wires are the input wires to check w/ ohm meter? could the speedo be sticking?