Signal level of ignition driver blue lead.

[WoodOnWater]

Hi all,
I am trying to get a Beede tach to function with my '73 Thunderbolt 500. I am not getting it to register through the tach lead. I believe that the Beede tach needs at least an 8v signal to register. I would think that the signal strength at the switch box where the tan and blue wires attach would be 12v though it is possible that the value would be otherwise. Most likely the blue lead controls the ignition sequence. The tan pulls the signal for the tach and goes to ground when the key is switched to OFF, killing the engine.

Does anyone know what the controling voltage of the blue Ignition Driver lead is?

 

[Faztbullet]

Re: Signal level of ignition driver blue lead.

The blue is the HS side of ignition and will carry 20+ volts. The 50hp with ignition driver used a special tach or regular tach with module to operate. Your best bet is to modify wiring and bring signal source off rectifier. The original tach was a Mercury A-91-45294A3 or 91-4816A6 and module 52552A3 .
http://www.ebay.com/itm/52552A-3-TA..._Accessories_Gear&vxp=mtr&hash=item43a9f77f7a

 

[WoodOnWater]

Re: Signal level of ignition driver blue lead.

Thanks, Fazt,

Two questions:

What does the module do to the tach signal?

Where would you pull the signal off of the rectifier? 12v output or off of the stator input to the rectifier? How many pulses per revolution?

Well, maybe four questions.

 

[Faztbullet]

Re: Signal level of ignition driver blue lead.

What does the module do to the tach signal?

Balances and clips voltage from what I remember.....

Where would you pull the signal off of the rectifier? 12v output or off of the stator input to the rectifier?

Stator input to rectifier......

How many pulses per revolution?

Should be 12 pole...............
You will need to modify wiring on internal harness so tan is not jumped to brn if you go with rectifier imput

 

[WoodOnWater]

Re: Signal level of ignition driver blue lead.

Should be 12 pole...............
You will need to modify wiring on internal harness so tan is not jumped to brn if you go with rectifier imput

Nice. I hadn't thought about splitting the jumpered wire.

 

[WoodOnWater]

Re: Signal level of ignition driver blue lead.

Tach is up and running. I'll be splitting out the jumpered wires. It was reading 1000 rpm at idle. Seems a touch on the high side. No matter. It's working and now it's a matter of dip switch setting to get it indicating properly. Your information was the key. Thanks.

Here is my project.

http://www.boatdesign.net/forums/powerboats/putting-all-together-15377-2.html

Post #13 was some photos.