Chrysler Repair: 94 lebaron convertible guage question, blown head gasket, voltage gauge

Question
Hi Roland, I have a 94 lebaron convertible with approximately 145,000 miles that within the last 2 weeks had an engine replaced due to a blown head gasket/head. Everything was fine after the replacement, however within the last 2 days it has developed a problem where the voltage gauge does not work and the temperature gauge is starting out at high(H).  I know it's charging and the temp is fine, but was wondering if you have any insight as to why just these 2 gauges would be misreading at this point.   As I understand the voltage regulator on this is at the computer and not at the alternator, but I could be wrong about that.  does it sound like a voltage regulator problem?

Thanks,
-Paul

Answer
Hi Paul,
I assume this is a conventional cluster with analog gauges.
The temp gauge is powered by a simple resistive sensor on the right side front of the engine with a violet/yellow wire and that goes to pin 11 of the black plug at the cluster. So check at the sensor for whether the wire is attached and if so then check the continuity of the wire to the cluster. The sensor should read more than 455 ohm when cold, and then it drops to 64 ohms when truly H. On that basis I suspect the wire is actually shorted to ground somewhere between the sensor and the cluster so check that possibility as well.
On the voltage, that is controlled by the pcm which manipulates the alternator. If the charging seems to work (battery voltage around 14v when the engine is running, then the issue is in the cluster. I don't see a wire from the charging system proper to the cluster, rather just a system voltage wire that also powers the other warning lamps and gauges at pin 9 of the red plug. So if that wire also is used to show the voltage reading then and it too shows around 14v then I suspect thate is a disconnect on the circuit board. You can look at the board between the pin and the voltage gauge to see if there is 'break' or cold solder joint.
There is a ground wire (black/orange) on pin 14 of the red plug, but if that were not connected the fuel gauge and other functions would also not work.
So I think the voltage gauge issue is in the circuit board proper. So look on the board where the gauge is located to find the connections of it and then trace those leads on the board.
Please read the PS below and respond.
Thanks,
Roland