Tachometer Inop

[pnora]

My 69 Chargers factory tachometer is inoperative. I have a Mancini ready to run distributor which has its own tachometer source. The tachometer was rebuilt 15 years ago and has sat in the box until I started putting the car back together. I assume it is ok. I verified that an aftermarket tachometer will work so the distributor is good. The power supply, ground and tach signal is present at the tachometer. From what I can figure out is the older tachometer electronics cant configure the signal. Has anyone had any experience with this?

 

[Demonic]

Yes. Tic-tock-tach as from the factory is points only. Buy the board from here:

https://www.rt-eng.com/

 

[Billccm]

I agree the rt-eng.com tach board is a great product.

 

[pnora]

I agree the rt-eng.com tach board is a great product.

I am aware of the RT boards as I have rebuilt several GTX and RR tachs. I was wondering if there was any tach adapters that worked to convert the signal.

 

[Billccm]

Do you have access to a function generator? You can check the tach operation with a function generator square wave. You can also verify your tach signal with an oscilloscope.

 

[Billccm]

http://www.average-guys-car-restora...ing-tach-for-68-road-runner-project-beepbeep/

 

[Billccm]

http://www.average-guys-car-restora...-for-68-road-runner-project-beepbeep-part-ii/

 

[pnora]

http://www.average-guys-car-restora...-for-68-road-runner-project-beepbeep-part-ii/

Thanks for the help. I was trying to avoid removing the cluster as the dash is back in. I did see this item which looks like it converts the digital signal the MSD creates. https://www.ebay.com/itm/142171581596?ViewItem=&item=142171581596

 

[rrTor-Red]

Thanks for the help. I was trying to avoid removing the cluster as the dash is back in. I did see this item which looks like it converts the digital signal the MSD creates. https://www.ebay.com/itm/142171581596?ViewItem=&item=142171581596

The cost + shipping for a relay? Here is one place you can get the same, as well as other sites too, but cheaper

https://www.wiringproducts.com/automotive-relays

 

[pnora]

↑
Thanks for the help. I was trying to avoid removing the cluster as the dash is back in. I did see this item which looks like it converts the digital signal the MSD creates. https://www.ebay.com/itm/142171581596?ViewItem=&item=142171581596
The cost + shipping for a relay? Here is one place you can get the same, as well as other sites too, but cheaper

https://www.wiringproducts.com/automotive-relays

What I showed is not an actual relay. It is a coil pulse simulator. From what I read the newer distributor creates a 12 volt square wave and will not drive the older style tachometer. This unit somehow interprets the square wave and converts it to a signal the tachometer will accept. For the 30 bucks I will roll the dice.

 

[Billccm]

There are various types of converters. In multi spark there are several pulses per actuation that need to be converted to a single pulse. A simple converter may just use a RC circuit to sort of integrate the pulses into a single sawtooth like wave. Other converters are a bit more elegant and accurate and use a pulse stretcher or one shot technique.
I understand the desire to not pull the cluster. Let us know how the converter works for you.

 

[pnora]

There are various types of converters. In multi spark there are several pulses per actuation that need to be converted to a single pulse. A simple converter may just use a RC circuit to sort of integrate the pulses into a single sawtooth like wave. Other converters are a bit more elegant and accurate and use a pulse stretcher or one shot technique.
I understand the desire to not pull the cluster. Let us know how the converter works for you.

Once installed I will let you know. The company that rebuilt my cluster told me that the tach was rebuilt and was rebuilt for the old point ignition. That was 15 years ago and it has been in dry storage until the recent assembly of the car. They said send it back and they would only charge for the parts to convert it to the new style electronics. If this conversion kit works fine. If not I know what I will have to do. I messaged the guy selling it and he seemed to be very knowledgeable on my situation. So we will know in a few days. Thanks for the suggestions.