HEI wiring help needed

[2BLACKZS]

Recently bought a 75 coupe that has a few loose ends...
I feel like a heal for asking but, there is a blue wire from the batt top side of the HEI that's been hacked. It's now spliced to what appears to be a temp sensor coil(?)... and has a non original in line fuse in the link. What a mess. Should the blue wire be spliced to a switched power source? Also, could this have anything to do with my tach not working? I just started working on this project car so please..cut me some slack..ha ha. Thanks for the advice.

 

[74bigblock]

... there is a blue wire from the batt top side of the HEI that's been hacked. It's now spliced to what appears to be a temp sensor coil(?)... and has a non original in line fuse in the link.

Sounds like someone felt the need to get power from the battery lead to the tach (Only provides power when key is in the "on" position). This is the concept you want to stick with, but I wouldn't recommend sapping power from the tach to run accessories.

... What a mess. Should the blue wire be spliced to a switched power source?

You should consider running a line from the positive lead of the alternator (Just undo the splice from your battery lead and move that wire over to the alternator positive lead with a brass ring connector. Keep the fuse in place... it's a good thing to have. You could also look to see where the "stock" lead should be in your wiring harness. Consult an assembly manual for a '75 on that idea.

... Also, could this have anything to do with my tach not working?

Doubt it. If you have an electric tach, Check the lead nect to the battery terminal on the distributor... follow that to your tachometer... Check for voltage. I recall that '74 was the last year for manual tach... so if you have one of those I'd be surprised.

Good luck!

Dave

 

[Bob Chadwick]

I'm at work and doing this from memory.

5 wires to the coil. Three near the distributor, two of which are from the controller in the distributor and the center is a ground. On the outside, the one near the firewall is the switched 12v power source and the other is the tach wire.

 

[bossvette]

from memory also there is/should be a 10 gage red wire to the bat terminal which is the switched ignition; a brown smaller(18) gage to the tach the other connector goes into the distributor.

 

[Jack]

Looking down onto dist cap ... with connections at 6 o'clock position ... inboard there's a 3-terminal buss that goes into base of distributor. Outboard of that is a 2-terminal buss ... the one on right goes to a switched 12V source (it carries 12V power to ignition system when ignition switch is "ON") ... the left one goes to your electronic tach (it returns tach signal to tach). All should be connected ... but nothing else.
JACK:gap

 

[2BLACKZS]

Sounds like someone felt the need to get power from the battery lead to the tach (Only provides power when key is in the "on" position). This is the concept you want to stick with, but I wouldn't recommend sapping power from the tach to run accessories.

By the way it's been wired, it does appear that the goal of the (former) splicer was a power source.

Thanks all for the assistance!

Wade