Engine Temp Warning Light?
 

72 C10 with the gauge package option 253, amp, oil temp gauge.

The dash light for this "Engine Temp Warning" does not work when KOEO or while cranking the motor over. I have 2 senders. One on T stat housing base with a green/white stripe wire to it and a sender on the head (6 cyl) that has what appears to be a dark green (possibly black) wire to it and is a heavier gauge wire than the one to the other sender

Which one of these senders is associated with the Engine Temp Warning light?

I did pull that bulb and with bulb in its socket continuity test fail, Blub test good. Scraped brass insert that bulb slides in and now have continuity with bulb inserted in socket.

Temp Gauge works.

Both senders appear to be original but the wire on T stat base appears newer so may have been spliced or replaced at some point in its life. I have not un-taped that loom to see if that wire color, green with white stripe, is continues or is spliced into another color, original, wire.

or is the Engine Temp Warning light with the gauge option nonfunctional?

Re: Engine Temp Warning Light?
 

The engine temp light with the gauge option is not functional. It is not wired.

Re: Engine Temp Warning Light?
 

Yes, temp light is non functional / not wired with the full gauge cluster. I believe the only reason it's even present is because it's part of the gas gauge assembly ... which is the same as used in warning light clusters.

As for the engine having 2 temp sending units, I think one of them may be a temp switch for TCS (Transmission Controlled Spark) ... an early emissions system that GM used on many early 70's vehicles.

Re: Engine Temp Warning Light?
 

It's a 3 OTT....

these pics show the sensor locations

One on head, DS and the other just under the T stat housing

Re: Engine Temp Warning Light?
 

Dang that's a Purdy engine bay

Wish mine looked like that

Re: Engine Temp Warning Light?
 

The 3 OTT trucks had TCS also. Mine did, but I don’t remember what color the wire was. I don’t see a TCS solenoid on your firewall by the heater box.