Swapping ammeter movement w/ a voltmeter?

[im02crazy]

I've done a lot of searches and did find this was nicely done on a later model Dodge, but nothing for a WM300 or earlier series.

Has anybody done an alternator bypass (is this covered by Medicaid:)and swapped the ammeter movement with a suitable voltmeter guts?

Any thoughts? I'd like to also remove the glass and re-mark the scale to match the other dials modified to read 8 12 16

Thanks.

[im02crazy]

update

A bit more searching and I found Redline. I'm including here in case others might have an interest in a custom gauge redo.

http://www.redlinegaugeworks.com/sretro_mopar.asp

[Gordon Maney]

I am unsure what you are meaning by voltmeter bypass. You could certainly use a voltmeter, and it would be very easy to connect.

[im02crazy]

Thanks Gordon for your reply. Once I remove the ammeter and wire directly to the solenoid I want to replace the ammeter gauge with a new volt meter movement. Probably a Sun CP7985 because it's movement is from the top and its sweep looks about correct. I will re paint the needle and face as necessary and mount it so it looks as original as possible.

I have found a few guys who seem to have successfully done this. The Redline site (in an above post) has a full gauge replacement for a "1948" Power Wagon that looks great, but beyond what I want or can afford to do.

I'm not sure what the type face is on the gauges, but I've found a close match.

[Clint Dixon]

I've done a lot of searches and did find this was nicely done on a later model Dodge, but nothing for a WM300 or earlier series.

Has anybody done an alternator bypass (is this covered by Medicaid:)and swapped the ammeter movement with a suitable voltmeter guts?

Any thoughts? I'd like to also remove the glass and re-mark the scale to match the other dials modified to read 8 12 16

Thanks.

I'm curious as to why you would rather have a voltmeter than an ammeter?

[im02crazy]

Good question. It's not necessarily one or the other, I have thought of installing a shunt type ammeter after the bypass rewiring. That way I could see the actual amp load being pulled, and the alternator output.

Here's my thinking on volt meter over ammeter:

(1) I don't want to run a full load to the dash, then to distribution,

(2) an ammeter will show rate of current discharge from the battery, actual load on the battery. The voltmeter shows the voltage output of the alternator and can be compared to the battery standing voltage by reading the gauge before starting the truck. When the truck is running and the alternator is charging the voltage should read about 2-3 volts higher than the battery reading,

(3) a fault of the ammeter or wiring would prevent the engine from operating,

Overall, the voltmeter would give a better instant reading of how the actual charging circuit is doing rather than the amperage condition of the battery. Depending on load, it's possible that the ammeter could show a positive reading but the alternator voltage could be below the proper 14 volts output.

I'm open for other thoughts or recommendations.

[74w300uteline]

Great explanation of bypass at madelectric.com

However it seems to be focused on w series trucks. Not sure if it applies to FF power wagons

[53Crusher]

Relay Kits

I left my ammeter in, when I converted to 12V with alternator. Gauge still goes to the positive side when charging. I am assuming if the alternator goes out, the gauge will drop or go negative. I've always got my hand starter crank if I lose charging on my battery :-)

Like you, I was concerned with running too many components from the ammeter post. I found a 5 circuit relay wiring kit that I mounted in the engine compartment. Although I bought a kit, I'm sure you could make one as well. My main power comes from the starter solenoid, One circuit was run to a fuse panel inside the cab and the others run items such as electric fuel pump, HEI ignition, lights and horn. I get the added benefit of fused power that can still be switched from the ignition key.

I found my kit here:
http://hyperwireperformance.com/

[Clint Dixon]

Good question. It's not necessarily one or the other, I have thought of installing a shunt type ammeter after the bypass rewiring. That way I could see the actual amp load being pulled, and the alternator output.

Here's my thinking on volt meter over ammeter:

(1) I don't want to run a full load to the dash, then to distribution,

(2) an ammeter will show rate of current discharge from the battery, actual load on the battery. The voltmeter shows the voltage output of the alternator and can be compared to the battery standing voltage by reading the gauge before starting the truck. When the truck is running and the alternator is charging the voltage should read about 2-3 volts higher than the battery reading,

(3) a fault of the ammeter or wiring would prevent the engine from operating,

Overall, the voltmeter would give a better instant reading of how the actual charging circuit is doing rather than the amperage condition of the battery. Depending on load, it's possible that the ammeter could show a positive reading but the alternator voltage could be below the proper 14 volts output.

I'm open for other thoughts or recommendations.

All good points. Thanks!

[im02crazy]

Thanks 53crusher, that's a really nice fuse and relay box. I looked around locally for one, but couldnt find anything that well setup.
Dave

[53Crusher]

Idiot Light

Dave-

One other thing you might want to consider (and I forgot to mention).
When I did my 12v conversion, I purchased a new Delco 10-si alternator. Ran the BAT wire to the starter, as well as the F2 terminal (most people just run this to the BAT terminal on the alternator). From my research, the F2 terminal gets a more accurate voltage reading for the internal regulator from the starter. The F1 terminal was run to a LED "idiot light" in my dash. When I turn on the ignition, the light is on. As soon as I start my truck the alternator kicks in and the light goes off. HOPEFULLY if the alternator quits charging, the idiot light will come on to let me know. This is a general schematic of what I did.

[jackw19]

Alternator Light

Crusher, how's this circuit working out for you? I plan to do similar on a re-wire of my 1957 PG W200.

Also, have you had any problems w/ longevity of the 12v LED? Do you have any additional LED protection not shown in your posted circuit?

Thanks in advance.

[53Crusher]

Alternator Light

Jackw19- Welcome!
I installed this circuit last May, so I can't really give you a longevity report yet :-) So far, everything is working as advertised. I chose the LED on the hope that it would outlast any filament bulb i could have selected. Time will tell.........

[jackw19]

Just One More Alternator Light Question

Crusher, what would happen to the charging system if the LED failed (presumably failed open)?

I've never really understood the alternator idiot light circuit, but I thought it was important that the field wire be connected -- to important to have it run thru a lamp. But that seems to be the standard alternator setup.

Thanks again.

[53Crusher]

one more question

I struggled with this concept as well when I wired it up. The idiot light is one of the few items on my truck that doesn't ground through the base of the light. It has two terminals + and - on it. The positive side of the light is wired to the ignition switch and the negative goes to the alternator. When I turn my ignition switch on, but before I start cranking the engine with the floor starter, current is running from the switch through the light and actually grounding out at the alternator causing the light to be on. Once the engine starts, the alternator no longer acts as a ground and that side of the circuit switches to positive as well. Since the light is getting positive current from both sides now, it doesn't have a ground and the light ceases to function. If the alternator quits operating, it should act as a ground again and the warning light would come on while the engine is running.
If the light itself fails, I will know it immediately before I try to start the engine. Better yet, the alternator can still energize itself at higher rpm and function properly, I just won't get any warning light upon failure until I replace the bulb.
I'm not an electrician and others on the forum may have better explanations than this, but I am comfortable with the function of the light now and hope you will be as well :-)