Hey guys, I have two 72's now and both of them have never seemed to have a functioning alt gauge. They never move or flicker they just stay dead center. Id like to start testing and figuring out how I can properly repair these or maybe just replace the gauge itself? Not sure where to start as far as testing to see if the gauge is ok. these have the printed circuit on the back of the guage cluster and I dont want to start sticking my power probe to anything im not sure about. Any thoughts questions or advice would be much appreciated. all the other gauges seem to work just fine speedo, temp,oilpressure,and fuel gauge (well it never reads right but moves somewhat accordingly if there is fuel or not in the tank) no dummy lights all real gauges.
Rich
1973 f350 super c/s 460/c6 22k orig miles
1972 f350 srw crewcab special 390
1972 f250 4x4 sport custom 390fe Red
1972 f250 4x4 custom 360 FE " Ranger Ric"
1972 f250 4x4 custom 84k og miles 390
1971 f250 4x4 sport custom 56k og miles. 360
1970 f250 4x4 428 fe hp60 205 d60
Dont eat yellow snow.....
disconnect the cluster from the wiring and run a 9 volt battery with wires to each side of the terminals of the gauge. if it swings over to one side o rthe other the gauge is good.
these alt gauges in these trucks never did move much if at all.
A 9volt battery? interesting. These gauges are just assentially ampere meters right? only showing charge discharge? Ill have to get a 9 volt and a clip that will fasten to the terminals with the two wires coming off it that I can connect to the gauge terminals. Thanks for the great reply Fordman!
Rich
1973 f350 super c/s 460/c6 22k orig miles
1972 f350 srw crewcab special 390
1972 f250 4x4 sport custom 390fe Red
1972 f250 4x4 custom 360 FE " Ranger Ric"
1972 f250 4x4 custom 84k og miles 390
1971 f250 4x4 sport custom 56k og miles. 360
1970 f250 4x4 428 fe hp60 205 d60
Dont eat yellow snow.....
There are two 4 amp fuses in the engine compartment for the amp meter. There should be two in-line fuse holders, one near the starter solenoid and one near the alternator/regulator. These are at each end of the resistive wire with the amp meter in the middle.
Ford uses a "resistive wire" instead of a shunt. The previous owner of my truck didn't like the shunt values and made a custom resistive wire. I must say it works nice, but I have no idea how do replicate it.
I went looking for the two 4 amp fuses. I found a couple wires with a plastic bulge in them that read "fuseible link" but I have no clue how to open them and check the fuse. You wouldnt happen to have a pic or maybe I can post what I found.... But I figured id check those out first its easy to do.
Rich
1973 f350 super c/s 460/c6 22k orig miles
1972 f350 srw crewcab special 390
1972 f250 4x4 sport custom 390fe Red
1972 f250 4x4 custom 360 FE " Ranger Ric"
1972 f250 4x4 custom 84k og miles 390
1971 f250 4x4 sport custom 56k og miles. 360
1970 f250 4x4 428 fe hp60 205 d60
Dont eat yellow snow.....
the fuseable link you found is a junction of several wires. dont bother opening it. it is a fuse in there. fuseable link means . that wire wire can burn in two if the wire gets too much through it. so the wire is basically a fuse in itself. if the wire burns into it has to be replaced with the same kind of wire so it will still be a fuseable link.
oooh ok. That makes sence. So the 4amp fuses for the alt guage are acually servicable? meaning I can check and replace with new fuses if they burn out? If thats the case I need to look harder...
Rich
1973 f350 super c/s 460/c6 22k orig miles
1972 f350 srw crewcab special 390
1972 f250 4x4 sport custom 390fe Red
1972 f250 4x4 custom 360 FE " Ranger Ric"
1972 f250 4x4 custom 84k og miles 390
1971 f250 4x4 sport custom 56k og miles. 360
1970 f250 4x4 428 fe hp60 205 d60
Dont eat yellow snow.....
i am unaware of any fuses other than in the fuse box on a 72. in 68 some wiring harnesses had a fuse on the inner fender. that i think was part of the charging system. i think. but ant fuse you find is replaceable.
Racer Z wrote:Yes they just show charge/discharge.
There are two 4 amp fuses in the engine compartment for the amp meter. There should be two in-line fuse holders, one near the starter solenoid and one near the alternator/regulator. These are at each end of the resistive wire with the amp meter in the middle.
Ford uses a "resistive wire" instead of a shunt. The previous owner of my truck didn't like the shunt values and made a custom resistive wire. I must say it works nice, but I have no idea how do replicate it.
Fordman, these are what im looking for if they exsist.
Rich
1973 f350 super c/s 460/c6 22k orig miles
1972 f350 srw crewcab special 390
1972 f250 4x4 sport custom 390fe Red
1972 f250 4x4 custom 360 FE " Ranger Ric"
1972 f250 4x4 custom 84k og miles 390
1971 f250 4x4 sport custom 56k og miles. 360
1970 f250 4x4 428 fe hp60 205 d60
Dont eat yellow snow.....
the 68 diagrams are the only ones that show the fuses. my 68 has the fuse . but itsnt a camper special and doesnt have a field relay. my inline fuse. which isnt hooked up. doesnt seem to do anything. it may control my alt gauge i dont know. since the alt gauge in these trucks barely works or moves unless something is really wrong with the charging system. if you have a fuse. it will be near the starter relay wiring loom on the passenger side inner fender.
you are correct, I checked out a 69 today and I saw the inline fuses....those are not there in my 72.....thank you for the referance diagrams....
Rich
1973 f350 super c/s 460/c6 22k orig miles
1972 f350 srw crewcab special 390
1972 f250 4x4 sport custom 390fe Red
1972 f250 4x4 custom 360 FE " Ranger Ric"
1972 f250 4x4 custom 84k og miles 390
1971 f250 4x4 sport custom 56k og miles. 360
1970 f250 4x4 428 fe hp60 205 d60
Dont eat yellow snow.....
I've got a '72 Camper Special with the same gauge issue. I've got the Ford Truck Shop Manual, which has a diagram for the charging system. There aren't fuses in the '72. Here's what I've researched:
The diagram shows a connection at the Alternator Output Terminal (Charge Out), with the wire running to a common connection between the Ignition Switch, the Ammeter Guage, and the Resistive Shunt Wire. (It doesn't show where the three-way connection is, but mine was under the hood, by the Alternator.) The connection to the Ignition Switch continues from the Ignition Terminal as a Green/Red Stripe wire to the "S" terminal of the Voltage Regulator, which can be ignored.
The other two wires from the three-way connection are the important ones:
One wire travels to the Ammeter Guage at the guage cluster, through the Alt Guage pc board, and continues back to a splice with the Resistance Wire, and then onwards to the vehicle battery. Wire colors are not identified. The Resistance Wire is run in parallel with the Alt Guage, spliced at the three-way from the Alt Out, and the feed to the battery. They are shown as spliced together and becoming a BLACK wire, which travels to the POSITIVE side of the battery. If I remember, the wire from the Alternator was black, too. They should be very heavy gauge wires.
Several important items to remember.
There was a Ford Service Bulletin about changing the Resistance Wire and connection at the Ignition Switch. I'll have to dig it up. Second, the Alternator puts out a lot of Amps, which need to go straight to the battery, NOT through the Amp gauge. The wires Ford used are large, but not large enough, in my opinion. The Camper Special had a heavy duty, dual pulley Alternator that could generate 140 Amps! You're talking #6 or #8 guage wire at 12 volts needed, not #10 as provided.
Under NO circumstances do you want the full charge of the Alternator to go through the wiring harness in the cab, to the gauge cluster and back to the battery. It will melt the insulation off the surrounding wires, which will cause the battery to direct short to ground. Turning off the Ignition Switch will do nothing. You'll get to watch your truck burn to the ground. Seriously.
The Resistance Wire is designed to handle 99.9% of the electrical current. A fraction of the charge current runs in parallel through the Alt Gauge (That's why a dinky 9 volt battery will move the gauge needle). Don't get the wires crossed up!
You're better off installing a Voltage Gauge, if you can. I'm looking for something that will look stock, and fit the Alt Gauge space, for mine.
Hope that helps, a little!
Ed Glenn, New Mexico
1972 F-250 390/2V, 4 speed manual.
Ongoing restoration project
Both my 69 and 70 have a plastic inline fuse holder at each end of the "resistive shunt wire". One fuse is near the alternator, just after the 3-wire connection, and the fuse is near the starter relay. These two fuses protect the amp meter and the shunt wire. Keep in mind that these fuse holders have had 40 years and many owners, they most likely have not lasted 40 years and have either been replaced or removed.
Good point about the fuses. I never examined my '68 or '70. In the 1972 Ford Service manual, there is a specific service bulletin, instructing the service tech to remove and bypass the resistance wire. The wiring diagram doesn't indicate the color, or location of the resistor wire.
Either way, the Alternator needs to charge the battery in a direct line, and the charging circuit shouldn't route through the cab dashboard.
As a matter of fact, if one of the fuses on the resistance wire went open, then the ONLY path for the alternator current would be forced through the Alternator Gauge. If anything should be protected with a fuse, it would be the Gauge!
Ed Glenn, New Mexico
1972 F-250 390/2V, 4 speed manual.
Ongoing restoration project
Not sure where to start as far as testing to see if the gauge is ok. these have the printed circuit on the back of the guage cluster and I dont want to start sticking my power probe to anything im not sure about. 
Any thoughts questions or advice would be much appreciated. all the other gauges seem to work just fine speedo, temp,oilpressure,and fuel gauge (well it never reads right but moves somewhat accordingly if there is fuel or not in the tank) no dummy lights all real gauges.
