replaced tach, still doing same thing

[azmusclecar]

1979 Olds, original tach was reading 500 rpms high at times. Does go to zero when key is turned on. Then when engine starts, rpms still go about 500 too high and
then becomes even more inaccurate at times. The needle does NOT sweep and swing.

Someone mentioned a ground issue but what ground is there to the tach?

Also I did try to solder a wire between the 8 and center contact to do away with the red plastic switch. See pic

I replaced the original tach with a new tach which still has the red plastic switch, and it is behaving the same way as the original.

Where would there be a ground issue????????

 

[Supercharged111]

Does it use a tach filter? GM went back and forth over the years about fitting tach filters.

 

[pontiacgp]

Have you removed the cap for the coil to make sure all the wires are good and in place?

 

[gnvair]

I had issues with mine. I by passed the tach filter and that rectified the issue. I have 6 tach filters that I collected over the years. All except one gave gone open.

 

[azmusclecar]

I'm not sure what a tach filter is, nor do I know where to find it if my 79 Olds has one.

Can someone please point me to the directions in finding it and how to bypass it?

 

[azmusclecar]

Have you removed the cap for the coil to make sure all the wires are good and in place?

I haven't done this, when I don't see the correlation between the two..........can you explain why this would be a possible source?

 

[fleming442]

It will be a capacitor, on the tachometer lead, screwed to the firewall, between the distributor and the bulkhead connector.

 

[azmusclecar]

It will be a capacitor, on the tachometer lead, screwed to the firewall, between the distributor and the bulkhead connector.

Ahhhhhhhh I'll check first thing tomorrow and see if I can find it. Thank you....hope you're having a blessed Easter.

 

[airboatgreg]

Do you have stock ignition?

 

[azmusclecar]

I believe THIS is the tach filter, correct me if I am wrong..........I cleaned contacts and jiggled wires, no difference. Are these available or can I wire from
the tach lead off the distributor right into the wire going into the firewall?????