Does the guage panel have an independent voltage regulator?? or could the problem be that the panel just grounded out?

I was driving, yesterday, on my way to pass my state inspection, when the Oil/ gas/ temp guages all pegged to the right, or high side. The electrical did not move. I first thought that the truck was overheating - but when I saw the other guages moving - I knew the problem was elsewhere. Are all three of these ground out guages? I know the temp is.

 

The voltage regulator is located on the back side of the gauge cluster and attached to the printed circuit. It is removeable and can be replaced.

 

The instrument voltage regulator is attached to the circuit board by a connecter that is exactly like the connections on a 9 volt battery. Just pull the old one off and insert the new one. Autokrafters(a sponsor of this site) sells replacements for $34.00.

 

This is a symptom of a bad IVR. All the guages (temp, oil, fuel) get common power from the IVR then 'sense' off the sender which is a variable resistance device that controls current through the guage. If you connect a test light to between the wire and the sending unit (or ground) you should see a pulsating current (the light should flash). Sounds like yours isn't, meaning that the mechanical part of the IVR has failed and is not breaking connection to reduce the overall current flow in the circuit.

As far as the amp meter goes, it does not take power from the IVR. If it works at all, it's not very accurate and if I remember correctly it is wired incorrectly to tell if you battery is discharging. You'd be better off with a voltmeter.

 

im curious about the ammeter wiring, please tell me more!

 

it is not a real gauge it doesn't work the needle is always in the wrong spot you should just install a nice after market triple gauge set with a real oil pressure gauge amp meter and coolant temp that way you know where everything is at.

 

Usually when all the gauges peg (except the ammeter) the instrument panel voltage regulator has lost it's ground connection. There are LOTS of threads on this problem here and how to fix it. The easiest fix is to clean the ground connection, a no cost option.

 

Ok, from what I've read on this thread the amp meter does not work off of the IVR. Got it.

The amp meter on my truck hasn't worked since I got the truck a couple of years ago. It's a 74 F350. Could the meter be bad or the wiring? Is there a test I could do to determine why it's not working? Or else I could just go out and buy an after market voltmeter as suggested earlier. Thanks.

 

There are several threads here on repairing the amp meter also. The basics there are again bad connections. pull the "nuts" off the back of the meter, clean the flex circuit, smear on some silicone dielectric, then re-install the nuts. Clean the other flex circuit contact points and smear them with silicone dielectric (spark plug grease). The dielectric grease helps seal the moisture and oxygen out of the metal to metal contact point. Clean the other connectors in the wiring harness and solder any bad connections. The ammeter works on a very small current produced by the shunt wire in the wiring harness. If there is any corrosion anywhere the ammeter will not work.

Corrosin in the crimp connectors and between the connectors themselves is the biggest problem with the electrical systems in these trucks. The next one is probably rust and dirty ground connections which is really the same thing.

 

amen torque1st, im going thru all the grounds on my truck and am learning that just because a cable looks ok on the outside it doesnt mean that its a good electrical connection!

 

The problem with ammeters in general is that they read charge if there is current going to the battery (if they are correctly hooked up). They read 0 if the battery is fully charged,..... OR if the alternator has failed! So how do you know which it is?

I don't think Ford's application of the ammeter was entirely correct. And it is prone to problems.

A voltmeter is much more telling as to the overall health of the charging system.

 

how do i get a good ground to the voltage reg

 

Just clean the flex circuit connections. Don't forget the silicone dielectric grease.


If the alternator has failed the ammeter will show a discharge from the battery.

The Ford ammeter worked great unfortunately if people wire around the shunt it won't work correctly or if the connections are corroded, which happens with a 25 year old vehicle.

I like a voltmeter myself. Since I am completely rewiring my truck I will be installing a digital voltmeter in the dash in the stock ammeter location. You can also install a 280Z voltmeter in the same location.

A LED digital voltmeter can be purchased from: http://www.hlabs.com/
http://www.hlabs.com/technical/instrument/, model VM-1

There are modifications to the unit that need to be made to control the display brightness. A relay, and a transistor to turn it on along with some other circuit changes are made. You can interrupt the trace to R1 (33 ohm) from the + 12 volt supply for dimming the display.

The 280Z voltmeter looks like the picture below. What looks like an LED to the right is actually a red lens that is illuminated by a light bulb. A person could probably rig up a comparator circuit to drive an LED for a charge light. I am not sure if you could use a STD Ford idiot light circuit to drive the light bulb but it could be looked into.

 

My 74 has a voltmeter that looks stock. Was the ammeter an option or stock and the voltmeter the option or did the PO replace with a voltmeter along the way? I am planning to rewire and want to be sure of what is supposed to be there. Thanks

 

I have personally never seen a voltmeter in one of the light duty pickups. Some of the HD trucks had voltmeters. The reason it is so hard to find a voltmeter for the LD trucks is that it is an upside-down gauge. Explorers and maybe some Rangers have upside-down voltmeters but they have no real voltage scale on them.