On my 99 VMAX when the grips are set to a comfortable temp with the adjusment dial the thumb warmer is way too hot... any ideas how to adjust or what may be wrong?

My 2003 Polaris does the same thing - and i have 3 positions for the warmer setting - i find them all to be too hot. I jsut turn it on and off as needed.

My 2003 skidoo also does the same thing on the thumb setting. I have to run it on the low setting and turn it on and off. The handwarmers on the other hand need to be left on High most of the time.

Perm

MABEE NOT THE ISSUE HOWEVER,
JUST BEFORE I STARTED TO BLOW ALL MY LIGHT BULBS.
MY GRIP WARMERS WERE GETTING SO HOT IT WOULD MAKE MY GLOVES STEAM.

THEN A FEW RIDES LATER THE LIGHTS ALL BLEW OUT.

TURNED OUT TO BE THE VOLTAGE REGULATOR..

I WOULD THINK THAT WOULD BE MAKING ALL GRIP AND THUM WARMERS TOO HOT THO.

IF I WAS YOUR PROBLEM..

It is just the nature of the beast, the thumb warmer always gets hottest. This is because the element is large for the surface area it has to go through, then it is also made out of plastic, which takes less time to heat up than the metal of the bars and plastic and rubber of the grips do. All this lack of resistance allows for the thumb warmer to heat up more and faster than the grips.

I had the same issue, it is normal. I fixed 4 of these sleds. Get a resistor for hot grips, and an on/off/on toggle switch. I mounted the switch just to the right of the hand warmer control. Find the wire coming from the warmer control that goes to the THUMB warmer, run this wire to the switch, on the high side of the switch, run a wire to the thumb, on the low side go through the resistor, and then to the high side. This will give normal operation when switch is set to high, no thumb warmer when set to off, and about half the temp to thumb when in low. I ran three sleds to over 10,000 miles set up like this. Thumb almost always on low.

Thats kind of ironic because on the 06's the handwarmers are too cold. :D