Fordnatics List Archive

This read-only message was archived from a public mail list.
Mail From: (email redacted) (George Chang)

I've dug into the instrument voltage regulators of two
Fords, both of which were close to being given away to neighborhood
kids. Maybe these points will be helpful:
1) The instrument voltage regulator (IVR) has nothing to do
with the black box that tells your alternator how hard to work and
when. The IVR sits on a printed circuit board and uses a simple
bimetallic switch to generate a pulsing current that averages about
half or a third of the battery/alternator voltages. This way your
instruments work, even if your voltage regulator (black box) is off
or your battery is low.
2) The corner auto parts stores don't stock IVRs. Maybe Ford
dealers do. Since my Fords were in such terminal condition, I took
the liberty of monkeying with my IVRs in good old shadetree fashion.
3) Your Factory Shop Manual has a good section on checking
the output of the IVR. I found it easiest to crawl under the car
with my VOM, disconnect the fuel level sender, and measure the pulsing
voltage at that point.
4) Since several of your instruments are off calibration
in the same way, there is a good chance that there is an IVR problem.
The IVRs on my old Fords had an adjustment screw that one could play
with. You can easily adjust the average output voltage, once you
open up the sealed can. However you should work very slowly and
carefully when you open the sealed can. It wasn't designed to be
reopened, and the parts inside are a bit on the fragile side. Also
be sure to make your adjustments in several small steps. Don't
ask me how I know!

I hope that these observations will be helpful. Good luck!

George