Hello Carl_Lab,
yes the temperature sensor is also fed to the main A/D, like V/A/Ohm
I strongly assume, that DCI , ACI are ok, but ACV is not working?
Have a look in the CLIP, analog PCB A1, 3458-66501, sheet 1/5.
There you see 8 relays, which feed signals of different modes into the DCV main input MUX, that is K3 (to R17). Input to this relay K3, are relay K5 for ACAL, the T- sensor from label W3A over K6, to ACV circuit over K9, and Ohm test current over K2. These should all work, and latter Ohm test current gives an Overload. Self test will not include input signals coming from the jacks, so there's the problem.
The signal from Volts Hi Input do not arrive at this relays MUX, so K1, K7 are not operating, either defect (both???), or they do not get proper steering signals from inverter driver U2, and from 'Defeat' FFs U22A,B. Check clear line of these FFs, pin1, or pin13, should be +5V normally, but maybe they are permanently shut off by the processor. overload detection, U10A and related circuit.
You could check first , if you get continuity from input of both relays pins K7-1, K1-3, 'Volts Hi Input', to the front jacks.
Maybe something is broken in between there.. see also input switching diagram
Frank
PS: I assume, that 100V and 1kV DC ranges give static zero reading, disregarding input voltage?