1970 Cuda Electric Gauge question

[elevenssc]

Here's the deal...I've noticed that the temp gauge on my 1970 Cuda slowly indicates hotter when I idle in traffic when it is 70F outside.  It goes back to the middle of the gauge when I get moving again.  I've upgraded to a 26" radiator, replaced everything in the cooling system accept for the wire that leads from the temp sender to the gauge in the dash, and the gauge in the dash.  The fan does not have a shroud, so I know that needs to be done.  However, I remember cruzing this car 20 years ago (yes, time does take it's toll on stuff), idling in traffic all night with a 22" radiator without any temperature issues.

The reason I ask the question is today, while idling in traffic, the temp gauge was indicating hotter, and my fuel gauge indicated emptier.     Once back at speed, the gauges returned to normal.  I'm thinking that this is now electrical related.

I know that these cars have marginal electrical performance at idle when new, much less when they are 38 years old.  Has anyone else experienced this phenomonon, or have I discovered a unique gremlin?  Is there a voltage regulator that I need to replace?  Upgrading the alternator is another option, any suggestions?

Thanks for your help

[FJ5_440]

This probably has more to do with the lack of a fan shroud than with an electrical issue.  While you are at idle, there is less air flowing through the radiator and less cooling going on.  The fan that was designed to combat that problem and move air through the radiator at idle is much less effective without a shroud to direct the airflow through instead of around the radiator.  You might also want to take a look at the clutch unit of the fan to be sure it is not worn out.  It is pretty common for the temp to go up a little when sitting at idle.  I don't remember my cuda doing that 20 years ago either, but I generally drove it like I stole it and may not have noticed the temp gauge unless the top of the radiator blew off.

[Chryco Psycho]

if it was a voltage issue both guages would move up not one up & one down , if the car is running lean or the timing is retarded it will heat more , I have solved more than a couple of heating issues by advancing the timing a few degrees & dialing out some of the vacuum advance as WSM can tell you