Jim's commentary on this subject is better than mine. I agree with the fusible
link or
installation of a fuse in the ammeter circuit.
My 58 NAPCO will be straight stock but I can hide a fusible link in there
easily. My
Chevy Sub will absolutely have AC at least and I'd like to do a slight upscale
radio/casette/CD player upgrade (original appearing radio, hidden casette/CD, no
gigawatt amplifiers necessary), but I want to keep the stock gauges so I may
have to
innovate here. I'll probably put a fuse in the ammeter circuit and look at
adding an
extra couple of circuits for the aux stuff, hidden, of course.
This has been a good calibration for me; itl's important to understand what
people are
comfortable with. I work in close proximity with this stuff on a daily basis,
and it's
easy to take it for granted and to become complacent. Just got done this last
week
helping a mech engr coworker size a current shunt, and isolated voltage
amplifiers (one
millivolt for the current shunt and one higher voltage for the load) to take
data for a
high voltage fuel cell power generation test (for a robot, not a car).
Good luck whichever modification you choose and Jim's right; be careful.
Mark Noakes
58/56 Chevy Suburban, V8, 3-speed + OD
58 GMC NAPCO factory 4wd, 6 cyl, 4-speed, original power steering, wideside
(fleetside)
59 GMC Suburban
Knoxville,TN
On Sat, 04 May 2002, J Forbes wrote
>
> Hi all...
>
> On the "could they be stupid enough to run all that current thru a
> voltmeter" thread...yes, they ran all that current thru an AMMETER. But
> things changed a few years later, when they used an external shunt type
> ammeter (really a voltmeter) on the trucks, as on the 1964 model that I
> just worked on. With this setup, the meter just measures the voltage
> drop across the big wire which connects the battery to the rest of the
> truck wiring.
>
> If you read the Ron Francis ads (he has been making wiring harnesses for
> street rods for a long time), you'll see that others have the same
> concern about sending all that current thru the dash wiring. Chr*sl*r
> products used ammeters at full current up till sometime in the 70s, and
> often had wierd problems when the ammeter stopped working...such as the
> battery not charging, etc. The old Chevy ammeters are very reliable,
> though.
>
> In a perfect world, I replace the ammeter with an idiot light (connected
> to the brown wire on the alternator). This allows me to run the red
> underdash power feed wire straight out to the battery connection on the
> starter, where I install a fusible link. These modifications make the
> wiring more like newer GM cars/trucks, such as the 70s and 80s models.
> The late late model GMs have gone to big fuses for everything, there are
> 2 big fuse panels on my wife's 99 Silverado! one underhood, one
> underdash.
>
> The solution? If you are using the truck in a normal way, with no power
> robbing accessories such as killer stereos, A/C, funny lights, etc, then
> you can use the stock wiring. Make sure the terminals at the ammeter
> are tight, and that the nuts that hold the spades onto the ammeter are
> tight. It'll work fine, I've been running my orange 59 this way for 25
> years, with no wire smoke. It wouldn't hurt to add a fuse link (4 gage
> numbers smaller [bigger number = smaller wire] than the main feed wire,
> such as #16 link for the stock #12 feed wire) where the main power wire
> connects to the battery cable.
>
> If you are going to completely rewire the truck, using one of those
> aftermarket harnesses, then replace the ammeter with a piece of red
> translucent plastic, and put a light bulb behind it (some fabrication
> required). The light connects to the brown wire on the alternator, and
> the ignition switch wire. This lets you know when there's a problem,
> and lets you run the power feed wire safely without worrying about the
> voltage drop thru the ammeter and all that extra wiring. You can run a
> properly sized feed wire (number 10) and a properly sized fuse link
> (number 14), and all should be well.
>
> THat's my take...please be careful with wiring, it can be dangerous!
>
> Jim F
> 59s in AZ
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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