Help with 92 XLT Fuel Gauge and Tach please

We recently purchased a 92 XLT 2WD in pretty good condition, but with a few issues. The first was the driver's power window, now fixed. The others that I'm now dealing with are seemingly common ones, but a couple of questions remain after having search this and other resources.

The problems (NOTE - I added other search terms in () to make it easier for others to find, including "guage" because that's how some seem to spell it ):

1. The fuel gauge (gas guage) seems totally non-responsive - it doesn't slowly fall as it might with a cracked float, it apparently isn't working at all. I understand the idea of checking ohms, but what's the best way to check? Is it removing the left rear tire and accessing the connector at the tank/pump, or ??? Any tips/tricks or specifics to check?

2. The tach (tachometer rpm) is doing the "jump to 3000" thing when the key moved to the on position - key on, engine off, prior to starting - and then remaining in the 3000-4000 once started, regardless of RPMs. I removed the tach, cleaned the pins and motor mounting screws, nuts, and pads, and reinstalled. Didn't fix it. I've found vague references to "a thing under the battery," etc., but nothing concrete. Any suggested tests, fixes, tips/tricks, anything? I can get a replacement at a wrecking yard, but I'd like to isolate it to the tach itself before I do this.

Thanks in advance for any ad all help.

was there any burn spots on the back silicone board? maybe in the top left?

i dont know what you can do with your gas guage... infact i did a search looking for information on how to fix mine and stumbled across your thread. but heres the problem with your tach...

when mine did exactly what you described, it was the fact there was some sodder joints in the back of it that were cracked. With the sodder gun i hit them for a min and it fixed them. a month later i havent seen a problem...

Some guys just went out and bought a new tach all togeather... $50 from ford. Others were able to just clean the 3 metal studs in the back of the tack (that plug into the back of the plastic cluster) and it worked fine.

if its not the tach, then its the coil pack... and if it was your coil pack then your engine wouldnt be running

its your Tach, i can bet money on it

I would check the tach as described above because apparently he had the same problem.

If that doesnt pan out it could also be the IVR, Instrument Voltage Regulator, behind the instrument panel.

The fuel gage is 90% probably the in tank sending unit, they get holes in them and the float no longer works, these trucks are NOTORIOUS for this.