Question.
I know resistance produces heat. But can the opposite happen?
Will heat from another object, cause resistance to increase in a circuit? Or at a suspected poor connection, even though the circuit is not producing its own heat.

Generally speaking heat increases resistance. So take a DC circuit at -40 and it will have less resistance then the same circuit at 100. So yes if another object is causing your circuit to absorb heat the circuit resistance will increase. Also a suspected poor connection if it is actually is a poor connection = increased resistance = more heat = more voltage drop.

Thats what i was looking for.
Thank you sir..

I only know what I learned in USN BEEP school…E=IxR.
Hope that helps.

In a nutshell, yes, a bad connection will produce heat ie..resistance.

Resistance of copper wire increases around 0.2% per degree F. A 100 degree temperature increase will increase the resistance 20%. Curious what the context of your question is. Under normal conditions temperature fluctuations don’t cause issues unless you are talking about extreme temperatures or wiring that was marginal to begin with.

Im chasing a very random issue with my truck.
It randomly idles up to around 1K rpm after driving awhile. Someone put a new pigtail for the throttle position sensor, so its spliced into the harness, not original.
I noticed only when the motor and engine bay is hot, i can wiggle the spliced portion and the motor will idle up, and i can also idle it down where its supposed to be by doing that, but only when at operating temp.
If you do it when its at the ambient air temp, nothing happens.... i was wondering if heat could play a factor in causing connection issues. I did find a poorly done wiring job under the heat shrink tubing. So i fixed that last night. No issues so far.
I just had a theory in my mind and wanted to know if it was possible.

A poor electrical connection is a catch 22 situation.

The current flow through a poor connection causes heat.
Heat causes the conductor and connection expand. Just as heating any metal causes expansion.
The more it expands the poorer the connection.
The more the metals expands, the worse the connection becomes.

And yes,external heat could have impact on connection due to the expansion of metal conductors.

I had a brake light issue. On warm days and a if you held brake pedal down for more than 3 minutes, I would get a light out signal on dash. After months of chasing ghost, it was an defective fuse, only failing when hot.

And... this situation is not confined to DC current, also applies to AC power as well.