Need help please to identify the problem!!

[72Z/28]

I have classic instruments gauges that were installed by the previous owner ( since 2011).

The tachometer and the speedometer used to work before taking everything apart to restore the car.

A digital tach was wired and it works fine but the analog gauge in the cluster does not work.

Regarding the speedometer, I realized that the speed signal generator ( classic instruments part no SN16) was not responding when hooking up a voltmeter while rotating the speedo shaft. So I installed a new speedo sensor for my Tremec TKO 500.

The car is suspended on 4 jack stands, so I turned on the engine, hooked the voltmeter to speed signal wire and ground at the classic instruments connector, put into 1st gear for slow rolling.

The volts started to alternate between battery volts and zero but the speedometer pointer in the cluster was not responding at all.

If the speedo pointer in the cluster was not responding, does this mean the gauge is bad and it is time to new gauge cluster

Will appreciate your input guys

[72Z/28]

Anybody?

[randy]

You sure you got all of your grounds connected?

[72Z/28]

Originally Posted by randy

You sure you got all of your grounds connected?

The grounds are connected and have a dedicated chassis ground for the speedo sensor.

[blitzer454]

Are other functions of the gauge cluster working like the blinker indicators and other gauges like temp, oil and water? If so then I don't think it's a ground problem. You mentioned that you installed a new speed sender, is the new sender still a SN16 or something else? Did you try going through the calibration steps?

[72Z/28]

Originally Posted by blitzer454

Are other functions of the gauge cluster working like the blinker indicators and other gauges like temp, oil and water? If so then I don't think it's a ground problem. You mentioned that you installed a new speed sender, is the new sender still a SN16 or something else? Did you try going through the calibration steps?

Yes all other gauges are are working except the tach and speedometer. The new sender is the SN16.

I am not sure whether the speedo pointer is supposed to move when just putting into first gear for a slow roll only as the car is suspended on 4 jack stands.

The tach, on the other hand, is sort of stuck at 1000 RPM and not functioning at all. I have heard that for LS swap, it requires a pull up resistor like 1K ohms 1/4 Watt.

I honestly have gone through the calibration steps

[blitzer454]

I agree you may need a pull-up resistor if you're using an LS ECM for tach signal. But I think the recommended value is a 5K 1/4 watt resistor so you might want to verify that value for the ECM that you're using.

Perhaps you won't see anything on the speedo at slow speeds until after you get the speedo calibrated. So maybe focus on getting the tach to work first then wait until you get the car on the road before worrying too much about the speedo.

[72Z/28]

Originally Posted by blitzer454

I agree you may need a pull-up resistor if you're using an LS ECM for tach signal. But I think the recommended value is a 5K 1/4 watt resistor so you might want to verify that value for the ECM that you're using.

Perhaps you won't see anything on the speedo at slow speeds until after you get the speedo calibrated. So maybe focus on getting the tach to work first then wait until you get the car on the road before worrying too much about the speedo.

Actually I ordered 1K ohms 1/4 watt resistor as it was recommended in some forums. Hopefully it will work. I have not connected it yet to see if the tach will respond or not.

As you said, may be I need to wait till I get the car back on the road to check the speedometer.