I just brought home my "new" 1989 D100, and on the way home I noticed the temperature gauge was reading very low, less than 1/4 of the way from cold to hot. Also, about 20 minutes into the trip the "MAINT REQ'D" light came on. Is the thermostat stuck open, or something else? The engine is a 318.

Did you check the coolant level before you began driving? Maybe it was low, or maybe there was an air pocket that finally worked out, or maybe something is leaking.

The thermostat could be stuck open, low temp could turn on a "check engine" light. The computer in that 89 moniters the engine temp. Gene

On my 06 Magnum RT AWD, I had the same thing, low temp and "check engine light" on . . . was thermostat stuck open . . . got it changed, and everything fine . . . welcome to the age of ECU's and computer control !

That light was required for emissions. Means to have your EGR serviced.Appoxmently every 50K. If I remember there is a switch behind the cluster to flip and reset. Shouldn't be causing any performance issues. You may need a 195* thermostat don't think the two are related.

Yeah, my mechanic told me the light was set to come on every so many miles. The low temp on the gauge I think is caused by the instrument voltage regulator. It looks like the fuel gauge and the oil pressure gauge are also reading low.

the older trucks had different gauge calibrations. All of my older Mopars read about 1/3 gauge when fully warmed up/