73 Electrical Gremlins

[ODZKing]

Has anyone ever had this issue? Installed a new heater motor last fall. First chance I've rally had to use it since the weather has been so crappy.
I was going to a cruise-in the other night with the 73 and had the A/C on. Everything fine until I switched the fan to high. Fan works fine but the oil pressure gauge and fuel gauge die.
Didn't notice at first and though, ooh better get some gas. Then I thought, wait I just put gas in this.
Not sure what made me try it but turned the fan off, gauges come back up (slowly as they should). Only seems to do it A/C mode, fine on vent, and on heat mode. And ONLY in HIGH setting, not med or low.
Switch? Something with A/C ... any ideas?

 

[oldbee]

First thought is weak ground.

 

[ODZKing]

As posted on the other forums, there was no issue in any of the heat modes, and it was at idol, driving, any speed.
So I went out to try a few things. First I tried unplugging the blower motor. and naturally with it unplugged I could hear the compressor kick on but no fan and no issue at full speed. All right, next plug the blower motor back in. Make sure it is tight and HUH! Problem gone. Now here is the part I don't understand ... IF it was getting a bad connection why did all 3 speeds work and furthermore WHY is it OK now? Connection obviously but?

I cleaned connection, bend the plugs a bit so they are presses together tightly and issue seems to have disappeared. I also put a new connector on the one end, may replace both at some point but I'm going to drive it for a while and see if this happens again. It is also right over the exhaust manifold on passenger side ... and is not a tight connection.

 

[oldbee]

That’s the way it goes! A little corrosion,less tension on connection (?). Ya never know.