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Discussion Starter · #1 ·
My 71 240 with automatic transmission had the distributor transplanted, it now has an electronic unit.

While working with the wiring to restore the tach to functional status, discovered two wires which come from the thermo relay below the coils on the left side inner fender.

The wiring schematic calls for the black wire to go to what appears the ground on the body of the distributor, and a Red Black wire to be connected to the negative side of the distributor and ignition coil. However, as soon as I make this connection, the car dies.

In order to check this circuit completely out need to know the location of a couple items. The thermo switch which actuates this relay, I would presume is on the transmission, but maybe I'm wrong, does someone know where it's at?

Next, I don't know what function this circuit does, does it purposely short out the distributor in case the transmission gets too hot or what?

The circuit in question is visible on the Late model S30 wiring diagram and not on the Basic model.

Can someone help me debug this, please?

Enrique Scanlon
 

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Re: 71 240 AT - w/ Elect Ignition - Thermo Relay H

The thermo switch and relay were used on the automatic transmission models to switch between the advanced to retarded sets of points (automatics had dual point distributors) under certain temperature parameters. Since you have converted to the electronic dizzy, just tape the wires off and forget about them. You can't use them unless you have some sort of a dual pickup system in the distributor. As far as I know there is no electronic dual pickup system to replace the dual point system AND retain its functionality. This was either emissions related or driveability related due to the auto trans. It was NOT a performance enhancing design like some of the aftermarket dual point distributors. I suppose you could use one of the dual pickup dizzys from a 280 and figure a way to wire the pickups to work through the relay, but if you have a good functioning ZX style dizzy, I don't think it would be worth the effort.
 

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Re: 71 240 AT - w/ Elect Ignition - Thermo Relay H

Thank you for the quick reply, wasn't sure what to do with the wires, other than tape them off.

Since the way I was taught to recondition vehicles, was that if the original wire harness had a wire for it, then there was a use for it. The only way to eliminate the use of a wire was if you could determine what it was worth and whether or not it applied to the vehicle at hand. i.e. automatic transmission harness wiring has a few wires not present for the manual, if using the AT wiring on a manual then ignore kick-down switch wire etc. conversely (as happened to me) if you get a manual transmission wiring harness then be sure to reproduce whatever AT specific wiring is required.

Thank you, printing your letter out and putting it into the Vehicle's Log

Enrique Scanlon
 
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