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TR2/3/3A A TR3A wiring question

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71TR6

71TR6

Jedi Hopeful
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I've installed a new wiring harness in my TR3A and came across this interesting green wire lead to the dash cluster. (yes, it is green rather than the black in the picture). There's a ring tongue with a lead coming off of it that goes to something else. The only thing I can figure from the schematic is either the wire end or ring probably goes to the fuel gauge but I can't figure out what the other goes to.

I'm sure someone will look at this and quickly say "yeah, that goes to _______" so guidance is appreciated!

Thanks!

IMG_0550.jpg
 
Green is power to the fuel gage with gr/bl going to the sender. Not sure why the maker left a pig tail
here ,might be a good power to the heater?? It is often good to check the continuity of each wire to confirm
that it is what its supposed to be, AM harnesses are always suspect.
Mad dog
 
If they are grounded....Those go to the speedo and tach (usually 2 eyelet connectors, but may be a separate lead between them). The heater was not included in the harness, since it was an optional. If they are powered, then I do not know...
 
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Got the flu..ran my edit time out. The tach and speedo are mounted to the leather or plastic and do not get a good ground...thus the need for the extra ground eyelets.
 
John is still correct. There are extra ground eyelets for the tach and speedo case to supply extra grounds for those dash lights. Usually 4 eyelets which loop around the case and hook to the brass knurled nuts and back to ground as a separate subsystem of grounds; they are black wires.

steve
 
Thanks everyone! I bought the harness from TRF (303004/CLO) in 2015 the year I bought the car (yeah, its been a long restoration). Looking at the schematic on the link Mickey provided, it might be a TR3 harness given the link between the wiper and fuel gauge. I double checked the TRF catalog site for that part number and it SHOULD be correct for the TR3A. (> Wiring Harnesses: Wiring Harnesses, TR2, TR3 Models B :(page 4) <)

I'll just start to assemble and with an eye on connecting the lead to the heater motor switch.
 
Just be thankful that you are NOT wiring a Tr6.There are 6 different factory schematics and only two
harnesses sold, to cover them all.The AM harnesses are a "compromise" and are not really correct
for any one car! Guaranteed to drive you to drink.
Mad dog
 
The wire will not be long enough to reach the switch. I'd connect it to one of the wires from the heater fan, run the other fan wire to the switch and then ground the switch.
 
There may be some confusion:

The ground wire from the heater fan goes to the the dash support bracket. The hot lead from the heater fan goes to the rheostat on the dash, and then to the chosen power source (the fuse, wiper switch, or ammeter). The heater rheostat is not grounded, except to the dash. (Note: make sure the heater is downstream of the ignition switch, so you can't run the battery down by leaving the heater switch on!)

There is no ground in the harness for the heater. It grounds directly to chassis via the dash support.

The harness does have a ground provided for the tach and speedo...usually 2 eyelets on a green or black wire. They go under one of the knurled nuts on the instrument mounting brackets. If there is only one eyelet, then a jumper must be used between the speedo to reach the tach. These grounds are only shown (in passing) on some of the wire diagram versions. Without them, the bright headlight signal and instrument back lighting will be intermittent, at best.
 
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John: what is the difference between what you suggest (ignition feed to the rheostat and ground the heater fan) and what I have seen on several cars (ignition feed to the heater and ground the rheostat)?
 
The hot lead from the heater fan goes to the green wire in your picture which comes off the fuel gauge.
steve
 
auprichard said:
John: what is the difference between what you suggest (ignition feed to the rheostat and ground the heater fan) and what I have seen on several cars (ignition feed to the heater and ground the rheostat)?
Click to expand...
The difference is if you want it as the factory recommended, "or", as someone over the last 60 years installed on the fly. If the question is "where did this lead go to from the factory harness", which is what I thought we were answering, then the answer is to the Tach and speedo. It has nothing to do with the heater. There are no wires provided for the heater in the factory harness. The heater came with it's own harness and instructions in the body section of the manual.

If you like, we could come up with a much better way than the factory did in, well, literally everything on the car! But,...your car, your choice. When the question is "is there a better way of doing it", then your way is an option?!?
 
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