Factory Tach wiring

[85_SS]

The tach filter (capacitor) is to help with radio interference, and from my experiences (and many others) it is not necessary. I bypassed it on my old 84 SS when it started acting up. Oldsmobiles didn't even come with them. Chevy's had them mounted on the firewall (needs to be grounded to work properly) near the distributer. Wiring goes from the distributer, to the tach filter, to the tach itself. I'm not sure if a Pontiac that orignally came without a tach would be wired for one, you will likely have to run your own wire (this is what I did when I installed a Rallye Pak cluster in my parent's 87 Cutlass.

 

[jae]

I have the Olds ralley pack guages with that switch on the back. Do I still need a tach filter? Will it hurt to put another one in, if that is a tach filter? I am rewiring my car, and did not find a tach filter in the old harness. I dont know if it came with one or if I lost it. I bought one just to be safe.

The switch on the back is for 6/8 cylinder selection. If you have an 8-cyl put it to 8; a 6-cyl, put it to six. As stated, if you have a filter it is there so that you can get a clean signal into the tach to get a proper reading, that's it. It's mostly for RF suppression, to help shield from interference / electrical noise. Follow the instructions, if you have them; again, some aftermarket tachs will have the filter since these tachs are for the most part universal. If it's a factory tach it may / may not have an inline filter;e may not be a need for it or it is on the firewall / under the dash or in the gauge pack itself.

If you want to experiment you can not run the filter and see how the tach reacts. If it is bouncy / erractic then you are possibly getting "noise" and you need the filter.

 

[Poncho-gp]

The filter would have to be hooked up or some wire would as it wouldnt have any thing running from the distributer to the tach Again this a Factory Tach with NO INSTRUCTIONS being put in a car that didnt come with a tach . I just need to know what the wire would wire into from distributer.

 

[dan2286]

The filter would have to be hooked up or some wire would as it wouldnt have any thing running from the distributer to the tach Again this a Factory Tach with NO INSTRUCTIONS being put in a car that didnt come with a tach . I just need to know what the wire would wire into from distributer.

Does the distributor have a terminal that is not being used where the connector plugs into? I think there would be an empty spot in the connector where the tach wire would plug into if the car came with a tach. If so you would need to get the brass piece that connects into the connector, connect a wire to that, and run that wire to the tach.

I dont know if the distributors are different for cars that came with a tach or didnt. From what I can see on wiring diagrams there is one wire specifically for the tach, so that terminal will either be on the distibutor and not being used, or it will not be there at all. If it isnt there, you will probably have to get a distributor/connector from a car that came with a tach.

Also, this is an HEI distributor, right?

Did you find out where to plug wire into at the back of the guages?