Low/barely registering EGT?

[Comatose]

I've had my plane since early July, and put about 40 hours on it in that time. 1966 M20C, with the ARI cowl.

Back in July and August my EGT gauge was working nicely, and it was always easy to set the mixture via EGT. Now that its gotten significantly chillier, I've had the following happen. I'm not sure if they're defects, quirks or just the way it is, as I haven't seen a season change before in this plane:

My EGT gauge barely registers. Maybe a little wiggle now and then, but I start running rough (and approximately at the mixture lever position I'd expect) before I get usable information registering on the EGT. It is WAY too low to lean 100 degrees ROP via the gauge, which is where I like to fly. I'm back to the old "pull it out til you run rough, then push in... some" routine.

On climbout my cylinder temperatures are where I'd expect, 390 degrees or so, but once I level off it is everything I can do to keep them in the green arc. On the low side. With cowl flaps closed. Oil temp is normal at 180 degrees or so.

My cruise speed seems to have picked up a little, but I figure that's mostly a function of the cooler temps. I had been cruising at 145ish knots at 7500 feet WOT/2500/100 ROP. Now I'm getting more like 150 knots.

The only thing that really bothers me is the EGT. Does anyone else have three-season-only gauges? Does any of this add up to something I should have checked out, or is it just the way it is?

[carusoam]

Do you have the simple Alcor single EGT gauge?

This is my favorite instrument.  It requires no electricity to operate, only the voltage generated by the thermo-couple itself.

Unfortunately, it does not come with enough strength to register the needle sometimes.  Or, the range that it is operating in falls off the scale.

Fortunately, there is a simple remedy and it is nearly readily accessable.  At the back of the instrument is a simple screw adjustment that allows for scale adjustment or exercise.

In the event that the gauge has gotten "rusty" exercise the screw.  In the event that the colder temperature has made the needle fall off the scale, make an adjustment....

Then purchase a JPI.....

-a-