Swapped my tired 79 distributor yesterday for a new MSD Street Fire and noticed what I had thought was a radio suppressor, attached to the tach power cable but is actually the tach filter, GM part 14020025 (discontinued). It still works but I figured it is 35 years old so should be replaced. I went to three parts stores to find a new one, but not available. I found one on eBay for $100 and some other places for around $50.
Here is a photo of the filter I found on the web.
I called Summit and talked with tech Tom who told me they don't have the filter but he is very familiar with the distributor and the tach and to disconnect the filter and throw it away because the distributor has inside what the tach needs to run. Not true.
Without the tach filter hooked up, the tach doesn't work. Plugging in the tach filter, the tach works fine.
I went on several forums and read that the filter steps down the voltage from 12 to 9 for the tach but I don't think that is true either.
Does anyone know what that device does, exactly? Does it step down the voltage or can I bypass it and just connect the tach power cable directly to the distributor? Notice there are two wires. I believe this filter completes the circuit between the tach ground and power. As I said, it still works but I am going to need a new one sometime in the future. Thanks.
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