Dashboard Amp gauge reading high.

Diagnostics with automobile dash gauges is like trying to diagnose pneumonia with a six-year old's Play Doctor plastic medic kit. Unreliable and vague would be a compliment.

My Doodge Spiritual's dashboard voltmeter says I have 12.5 volts running down the road and around 8 volts with the air conditioner and lights enabled. Of course the readings are absurdly in error. Perhaps on a par with one of those 8-Ball fortune telling toys.

I will list this for drill.

The work involves tapping into one of the three or four alternator stator to rectifier connections. Solder a stub, a connector, then run a single wire into the cab.

That wire gets connected to a standard Bosch relay. Right to one of the two magnetic coil connections. The other connection goes to chassis negative.

Ignition powered wire to the perpendicular power terminal of the relay

Exiting the CENTER terminal of the relay, another wire runs to the inlet of a warning lamp, an audio piezo alarm or both.

AC voltage from a stator connection to chassis negative is 8-volts. Enough to pull the relay contact points apart. This cuts the alarm circuit.

But if the alternator fails to charge and the ignition key is turned on, current will flow through the relay contacts and to whatever alarms are present. Naturally with the key turned off there is no power to the contacts.

Not only alerts the driver to a failed alternator but also to a thrown drive belt.


I've used this circuit successfully for decades.

I think you have found your problem! A Bad battery!

Took the van for a drive today and noticed that when I am stopped at a traffic light with the headlights and heater fan running full blast the needle would drop below 0 on the gauge but when I pulled away the needle would go back up above the 0 mark.
Also noticed the voltage gauge for the 2 house batteries was at only 12.32 after being plugged in for 3 days.

in my old 72 dodge
i installed a 5v flat pack regulator, heat sunk it to the dash, PN 7905?
cost 75 cents

i used Drock buck converter to fix the 12v regulation problem in 95 Safari DP
i also had to fix a ground problem with the dash board gauge panel

Im well aware all the parts books list the widespread external mopar VRs that were used well before, but after 1988 on the 318 engines, and after 1989 for the 360 engine, all Dodge vans use a voltage regulator internal to the engine computer until they stopped making them in 2003.

The dashboard voltage regulator is seeking to hold 5 volts. The technology to hold this voltage is from the 1930's, and costs 37$ for a new one.

I instead installed a 3 amp Drok buck converter for under 7$.

I do not know if the stock dash ammeter is requiring this 5v source or not, Mine has been gone for many years now.

I looked VR up for a 1990 B250 with 318 or 360 engine and both showed the flat firewall mounted solid state regulator we had on our 1970's B300 used.

In that van, there was a little VR on the back of the instrument cluster. I'd get erratic readings if it was bad, OR the ground connection was loose. Small metal-cased thing, not much bigger than the small automotive circuit breakers. If I became alarmed at rising Coolant Temp, I'd notice I also had More Gas and Higher Oil Pressure than just awhile ago. Knew it was time to work on the Cluster. I don't remember if the Ammeter was also affected.

I have the same vehicle as the OP but one year earlier. The engine computers are interchangeable.

The voltage regulator is inside the engine computer, not the alternator.


Does your alternator look like this?
But double V belt pulley.


The dashboard Ammeter on mine, the needle did not move enough to alert me to alternator failure in 2004. A simple voltmeter would have. These Ammeters are not the same mopar ammeters of yesteryear, which funnelled a lot of current through he firewall.

The only times I saw the stock ammeter gauge raise a significant degree on mine, was when the engine battery itself was well depleted in addition to the house battery, and this happened only as long as the engine computer chose to seek 14.7 or 14.9v right after startup.

Usually the engine computer would seek to attain/ hold 14.9v for a few minutes then was 13.7v max with the occcassional blast back upto 14.9v for no discernable reason.

A tachometer now resides where the stock Ammeter did.

I will Theorize that perhaps your engine battery is not isolated from house loads due to 'isolator' failure.

BUt I would just throw my DC clampmeter over a cable first and see if high amps are indeed flowing into engine battery. Then the same for house battery.



Usually if the VR in the engine computer fails, then there is no charging occurring. Voltages with engine running will be below 12.8 and keep falling.

What is your voltage when your ammeter reads sky high?

Are the fuel gauge and temperature gauges also reading high?

Have you cleaned the engine battery post clamp surfaces, and the battery to firewall ground( behind battery) and the battery to engine ground?

Any other weird electrical occurrences?

Have you pulled the computer codes via the 'key dance'

There are ways around having the engine computer regulate the voltage with this vehicle. I spin a pot on my dash and watch voltage at battery terminals, and amp flow into the battery, respond accordingly.
It gives me joy. It is enlightening.

Ignore it and go.

Dashboard ammeters are notoriously inaccurate.

First, clean the battery terminals and the top of the battery. At a minimum, spray it down with a strong spray from a garden hose. Max sure the battery terminal on secure.

Get a digital multi-meter. The $6 Harbor Freight meters are not very good, but their $24 meter is not bad. Craftsman has a few to choose from in the $35-$50 range. No need to spend more than that.

• Check and record the battery voltage before starting.
  It should be between 12.0 and 13.0
• Turn the key on, high beams on and heater blower on high for about 5 minutes.
  Check and record the voltage. It should be above 11.0
• Start the engine. Check and record the voltage. At a high idle, it should be above 13.8 but below 15.0
• Go for a 10-15 minute drive with all accessories turned off. Check and record the voltage at idle. It should be between 13.2 and 13.8

The last reading is the one that would indicate over charging. But over charging could be caused by a high load.

Some Chrysler/Dodge vehicles from a bit earlier than the OP's rig did have ammeters.
Have you added anything lately? It's possible to add a load down stream of the gauge and have the meter show a higher reading than it really should. I have a vintage car that did this after adding a rad. cooling fan. Doesn't hurt anything.