Hi, Since you are new to the hobby (congratulations) is your antenna
correctly mounted (grounded OK)? How is the coax cable run, could you
have "pinched" it
or cut it pulling it through metal parts of your car, maybe causing a
short in the cable?
It sounds like it is an antenna issue. It sounds like the radio is
folding back it's power
for protection. If you don't have an swr meter, get one or borrow one.
Also, see if you can borrow a magnetic mount antenna for a quick test. If
that works OK then it is an antenna / coax problem. One more thing you
can try if your antenna seems ok.
Add a small coax jumper (a foot long or so) between the radio and the
antenna coax. Once in a blue the added length of coax can cure some SWR
problems.
73 and good luck!!

Dan wrote:

I just got my first mobile, a used HTX-212 (45W on high power).. When
I have the car engine off the transmit bars only light up about half
way. When I drive they go up farther but I still have trouble hitting
the repeater while my HT hits it with no problem. Are these power
fluctuations normal?

Thanks,
Dan
KE5BCC