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TR5 & TR250 Forum

Alternator wiring

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TRZ250 Tom Z
Reedsburg, Wisconsin, USA   USA
I've replaced an alternator on a TR250 with the Delco7127 SI type. Everything has gone well and it fits in there nicely, but I'm not quite sure about the wiring configuration. The instructions from one of the other threads was specific to a TR6 and the wire colors don't quite match up.
So, the TR250 had a 4 wire hookup with a Brown/white (approx. 10 GA.) wire which obviously goes to the battery.
The second wire is black and is obviously the grounds.
The other two are about 14 ga. with one being brown/yellow and the other brown/green. There are two tab connectors on the alternator, #1 and #2. Based on the TR6 instructions I would assume that the brown/yellow goes to #1 and the brown/green to #2. Is this correct?
What throws me for a loop is the external regulator, the new one is internal, so how would the external one get disconnected in this hook up.
Thanks

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Easy method is to just pull the plug off the external regulator, add a jumper between the brown/red and brown/green wires, and tie the plug up someplace. Then brown/yellow goes to pin 1 on the Delco and brown/green goes to pin 2.

BTW, you may want to add a shunt to the ammeter, as the Delco will way overdrive it when you first start the engine. Perhaps the TR250 version is more rugged, but my TR3 ammeter has started to stick at full scale after just a few dozen starts.

I think (not certain) that 8" of 16 AWG should be about right to convert it to 60 amps full scale. (That is based on a measurement a friend took on his 72 TR6 ammeter, which I am assuming is the same as the TR250.) One way to check is to turn on the headlights (engine off) and note the reading without the shunt, then install the shunt and try it again. If you get about 1/2 of the reading noted without the shunt, it has doubled the full scale value.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild



Edited 1 time(s). Last edit at 2017-02-05 10:08 PM by TR3driver.

TRZ250 Tom Z
Reedsburg, Wisconsin, USA   USA
Perfect, just what I needed. And thanks for the tip on the shunt.

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