waiter;

That 14 volts is most certainly too high as an output, and it suggests the unit is shorted from input to output...and routing an unreduced battery voltage through to the gauges...if this was a thermo-mechanical unit that symptom would point to the unit not cycling, but being an electronic replacement, it is shot electronically!...more here: http://sw-em.com/voltage_stabilizer.htm

If your electronic replacement of the OE thermo-mechanical is not lasting, I suggest there are only two possibilities:

1. The replacement was faulty and died under electronic infant mortality...possible...was it a commercially made unit or a homebrew? Please give source and any other data on unit...maybe some other readers can post experience/missexperience with same unit. OR

2. It is being hurt because of the loads it is subjected to have increased to a level beyond what it is intended to supply...are the gauges powered by it working OK? have you made any changes to vehicle E-Syst?...can you measure load current on VS...unless someone can post an actual measured current magnitude, I expect it should no more than a couple hundred milliamps (strictly my estimate).

1a. [I just thought of this additional one...it's really an extension of No. 1.] VS is being hurt by overvoltages caused by loadshedding when turning of inductive loads such as Blower, Wiper, Starter etc. (this suggests a poor ground at those loads...very possible in a vintage vehicle, but this SHOULD have been taken into account and accommodated in the design of an electronic replacement unit, with an overvoltage clamp of some sort).

Please post back with your resluts/findings!

Good Hunting!