Volt Gauge

[Paul in MN]

Wiring to voltmeter

All good reading.

Where is the best place to pickup the power going to the volt meter ?

I know it should be a keyed power source, but should I tap into a wire, plug a spade into the firewall connector, or run a wire all the way to the fuse box ?

I don't know the wiring of your truck well enough to give you a really good answer. Does your truck have 2 heavy leads connected to the back of the ammeter, one heavy lead to each screw terminal? If so you can attach both of those heavy leads to a single terminal on your new voltmeter, and connect the other terminal of the voltmeter to a good ground. This may sound strange (like are we creating a short circuit and putting everything at risk of melt down?). Just remember that a voltmeter is internally a very high resistance (1,000s of Ohms) so it limits the amps flowing through the ground wire to a few 1/1,000s of an amp.

The ammeter is an extremely low resistance device, it is made to be a "super conductor" possibly capable of conducting 100 amps. So if one side of an ammeter was connected to ground, the wire and insulation will burn almost immediately. As we are changing from ammeter to voltmeter in the dashboard instrument panel, we MUST be sure to understand the differences between the 2 different meters.

As to your specific question of where to hook up the voltmeter, it just becomes a matter of convenience, and yes I agree that it should be on a switched circuit, otherwise it will be a constant low level drain on the battery. Where behind that instrument panel can you find a key switched wire that will be "hot" any time the truck is running? The OEM's use of so many plastic shielded connectors makes that difficult, so use your DVM or DMM (volt scale!) to find the easiest place to hook on to for the + side of the voltmeter. The - terminal on the voltmeter needs to be wired to a ground, and you will probably find many groundings on the sheetmetal braces under the dashboard.

I hope this has helped.

Paul in MN

[n1265]

Well I did the Amp bypass last night, I decided to butt splice the black and red wires together at the amp gauge, solder then shrink tube them. ( I did this to get rid of the ring terminals I installed when I re ran the wires threw the firewall to get them out of the firewall connector)

The + lead for the volt meter I picked up from a switch for my Plow light ( rotating beacon ) and wired the light for the volt gage into the clearance light provision that was not used on the M880.( brown wire ) A pretty straight forward install, I used 16ga. wire. ( all connectors are crimped, soldered and shrink wrapped)

However, I am still not happy. when idleing, instead of my lights pulsating and the Amp gauge bouncing around, now my lights pulsate and my Volt gauge bounces around.I was really hoping that doing the bypass would help solve this.

Also, In anticipation of doing the 100 Amp Alt upgrade, I also ran a 8 gauge wire straight from the Alt to the starting relay. this is in addition to the stock 10 ga wiring that I just spliced together at the Amp Gauge.

Could running two charging wires to the starting relay cause this problem ? or any other ?


Also, On the back of my Volt gauge there is a terminal that is marked "S" with a plastic cap on it. What is this for? is it some kind of adjustment ?

when running the gauge reads between 14-16 volts.

[MoparFreak69]

Pulsation at idle tells me your voltage regulator is having troubles. There is supposed to be a diode circuit within it to keep the voltage at a nice steady level without any peaks (a diode could have failed which is probably what is causing your pulsation).

Having 2 charging wires shouldnt cause this. It will just provide an extra amount of conductor for the electrons to flow from the alternator to the battery.

If it is really bothering you I would consider moving up the alternator swap deadline to eliminate one possible source of the problem. Regulators are not that expensive, if you are going with an externally regulated alternator I would consider replacing the regulator at the same time. Avoid the import units if possible, they seem to be troublesome and not very reliable.

[n1265]

I have a new $40 Mopar external reg that I got threw summit sitting in the box waiting for the 100 amp alt. install

I have been holding off getting the new alt because the plowing season is coming to an end and the new re-man alt on there now only has 3k miles on it. But with it charging at 14+ volts maybe the reg it taking a Shi* It is new also but I have read where they do not last long
( China product from Autozone )

[MoparNorm]

The gauge needed for any wire is determined by the number of amps expected as maximum to flow through it (and total length of wire). Commonly a #12 gauge wire can adequately carry 20 amps continuously, #14 15 amps, #16 10 amps. In the case of wiring up a voltmeter, it is probably in the range of 1 to 10 milliamps, meaning probable maximum of 1/100 amp. Different gauge manufacturers will have slightly different numbers for current flow. But this range is adequate for this discussion.

A volt meter measures voltage from the + side of the truck's electrical system to the - side. It makes no difference where this measurement is made... at the battery, at the dashboard, at the cig lighter. The highest normal voltage is expected to be close to 15 volts as the battery is first charged, settling down to 13.2 volts. With this low voltage, and the extremely low amperage, the smallest of common wire gauges is adequate. And in your wiring supply, this might be 20 gauge. The advantage to using this thin gauge wire is the prevention of electrical fires. A very thin wire, if abraded by rubbing on a sharp sheet metal piece behind the dashboard, will quickly heat up and burn out acting as a fuse protecting the rest of the wiring from overloading and overheating. POOF!!!!, the thin wire is gone, there is some smoke and stink, the voltmeter no longer works, but that does not prevent the rest of the truck's electrical system from working normally, and it does not prevent the truck from running.

The wiring to an amp gauge is quite different, because it is built to carry temporary overloads of 60 amps or more as the alternator begins to charge a very dead battery. Thus the very heavy 8 ga coming off the alternator, but if its insulation is abraded (and resuls in grounding), the electrical harness is destroyed, and quite possibly the truck is burned. Lesson learned: do not use any heavier gauge wire than its particular circuit needs. I did learn this lesson in the college of hard knocks, a grad level course. The tuition was pricey.

Paul in MN

Good info.
Also at issue is HOW Dodge wired these trucks, back in the day, when generators and alternators were in the 35 Amp range it wasn't that big of a deal, but with high output alternators, running the primary voltage from the alternator to the Amp gauge BEFORE routing it to other components was the true culprit.
I just re-wired to by-pass the melted amp gauge and installed a volt meter in it's place. I like the theory of an amp gauge, but a volt meter has it's purpose too.
I picked up a gauge from Summit that is a "top down" needle just like the factory gauge and with a little customization, got it to fit into the stock cluster. I'll post a photo if I have one.

[KRB64]

freakin regulators...

You can get a MOPAR regulator at Summit cheaper than at the formerly known as Dodge Dealer. $25 vs $40!?!?

Why does this say for drag racing only?
http://www.summitracing.com/parts/DCC-3690731/

[n1265]

I don't know, But I'd like to. I just bought a black one from summit a few months ago, Mopar for $40....


would love to know what the difference is.

[MoparNorm]

You can get a MOPAR regulator at Summit cheaper than at the formerly known as Dodge Dealer. $25 vs $40!?!?

Why does this say for drag racing only?
http://www.summitracing.com/parts/DCC-3690731/

Because it puts out a constant 13.5 volts. In a stock system with alternator and battery, that would be called a welder.... = )
It would quickly burn up stock diodes in the alternator... and about anything else in the stock electrical system.

You want this one:

http://www.summitracing.com/parts/DC...76&prefilter=1

[MoparFreak69]

Why does this say for drag racing only?
http://www.summitracing.com/parts/DCC-3690731/

This regulator is designed for a drag car. When thinking drag car you need to think light weight. What weighs about 50 lbs and isnt needed to go from 0-300 in 4 seconds? A battery. This regulator allows you to run the engine/alternator without a battery, but not for very long periods at a time. As MoparNorm mentioned this is very hard on alternator diodes and therefore alternator life is drastically reduced. Drag racers dont care because when they have the need to delete the battery that means the engine is probably only running for about 20 seconds. 10 for the burnout and 8-10 for the trip down the strip. Usually tow rigs bring these types of rigs back to the pits.

[KRB64]

Because it puts out a constant 13.5 volts. In a stock system with alternator and battery, that would be called a welder.... = )
It would quickly burn up stock diodes in the alternator... and about anything else in the stock electrical system.

You want this one:

http://www.summitracing.com/parts/DC...76&prefilter=1

Thanks for the clarafication guys.

That MOPAR one from Summit looks more MOPAR than the one I got from the dealer. The dealer one matches the silver, plain cased ones I get from NAPA. I think I got took...

I asked them about the orange ones I used to get and they said they didn't do them anymore? Course the counter kid was young...

"I picked up a gauge from Summit that is a "top down" needle just like the factory gauge and with a little customization, got it to fit into the stock cluster. I'll post a photo if I have one." What was the Summit # for that one?

[MoparNorm]

I asked them about the orange ones I used to get and they said they didn't do them anymore? Course the counter kid was young...

"I picked up a gauge from Summit that is a "top down" needle just like the factory gauge and with a little customization, got it to fit into the stock cluster. I'll post a photo if I have one." What was the Summit # for that one?

The Orange box (ECU) comes standard with the Mopar Performance Electronic Ignition Kit, not sure about an orange regulator?
I won't be at my shop until sometime late tomorrow, but the Summit number is...http://www.summitracing.com/parts/SUN-CP7985/

Keep in mind that the "SunPro" lettering at the top is a part of the cover that is discarded. Except for the blue range band, it is identical to the factory unit in appearance. When you see the finished gauge, you will see how nice it came out...and most importantly, the owner is happy... = )

Not too many choices in a "top down" gauge needle.

[KRB64]

The Orange box (ECU) comes standard with the Mopar Performance Electronic Ignition Kit, not sure about an orange regulator?
...

Maybe thats what I'm thinking of.

[MoparNorm]

Crummy iPhone photo, I forgot my camera...doh!
It looks pretty good sitting in the cluster.

[n1265]

That does look good .

[USN78W150]

gauges

Mopar Norm,
You need to complete that cluster with an oil pressure gauge, sir. :)