[DeTomaso] Fw: Fw: More Problems....

[Will Demelo]

Hi Bill.
I am using an 8910 tach adapter. This the one I was using before the spark incidence and it worked. I believe the difference is that one is current limiting and the other is not.
Is anyone else using an 8910 out there?
The white wire between the 6AL and the tach adapter are connected together with the original coil wire. This connection should be voltage to ground, correct?
Also, the red wire (not violet on my 8910) is connected to the red wire on the 6AL along with the switched +12v wire from the ignition circuit. When testing the red(violet) wire for voltage, do I disconnect the red wire from the tach adapter and test to ground while running and look for AC value? or do they stay connected and test to ground? 
Thanks will

----- Original Message ----- 
From: SOBill at aol.com 
To: wdemelo at cogeco.ca 
Cc: detomaso at realbig.com 
Sent: Friday, May 16, 2008 1:45 AM
Subject: Re: [DeTomaso] Fw: More Problems....



Will,

You can verify that the 8920 (if that is what you use) is working in the car using a multimeter.
With the engine running the White wire between the 6AL and the 8920 should read around +2.8 V DC. This indicates that the 6AL is providing a 20% duty cycle +12 volt square wave to the 8920. This voltage will not change with the speed of the engine because the signal duty cycle % does not change. If the White wire reads 0 V DC, you may have a bad connection. If The White wire reads +12V DC, the 6AL tach output signal is bad. If the White wire different than +2.8 V DC, something is wrong with the 6AL.

With the engine running, the Violet wire tach signal out of the 8920 should read as follow:

1,000 RPM = 1.27 VAC, 2,000 RPM = 2.62 VAC, 4,000 RPM = 4.75 VAC

This indicates that the 8920 is putting out the normal point/coil type signal to trigger the Pantera Tach. Note that we are reading AC voltage here because we want to see the inductive ringing signal which occurs with each spark occurrence. The AC voltage on the Violet wire increases with engine speed.

The 8920 tach adapters are a potted assembly and cannot be repaired

I have an MSD 8920 tach adapter I use for testing tachs when I repair them. I would be glad to loan it to you.

Have fun,

SOBill Taylor


SOBill Taylor
sobill at aol.com





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