Something's not right. Both on voltage in and voltage out. Voltage in to the board is 12-13.5V DC, cleanly measured by a decent multimeter, as it is straight juice from the harness.
If you're using an original instrument panel voltage regulator, rather than one of the new solid state units, the voltage cycles from 0-12, giving a sort of averaged 5V signal. Pretty goofy, but a digital multimeter has a hard time giving you an accurate measurement because of the cycling. The old "mechanical" IVR's use a bi-metal strip that heats up when connected, causing it to deflect and break the circuit. As it cools down, it reconnects, until it heats up and deflects, ad infinitum, hence the on/off 0v/12V output. Most digital multimeters have a damping function to smooth the voltage readout, the damping gives very low readings as for the output. Old needle style units will usually show the pulsing, and the actual voltage out.
Alternately, if you put a test light on the signal out from the IVR, an old mechanical style will visibly pulse on and off. If it pulses bright, your IVR is working.
First step I'd take is to throw away any old style IVR, and put in a new style solid state. Period. Every old bimetal IVR I've bought in the last several years didn't work, or failed very shortly after being put in. The solid state units have been reliable for me.
As far as the circuit board, they are easy to check out continuity of the traces. If there's continuity, the only other problem can be grounding between a trace and the instrument cluster case. Make sure the instruments themselves are properly centered, so that the posts don't touch the case, and that all the insulators are in place, there should be no problems. I've used several repro circuits, have yet to have a problem with one.
Carl
