Wiring an ammeter

[Tinman]

I know ammeters aren't very common and are hard to find. But I have one on my 01 are really like it. I installed one on the 06 but it isn't picking up the charge of the alternator. I noticed the alternator is wired to the passenger battery on the '06 but it shouldn't matter. Both trucks have VDO externally shunted gauges with the shunt in the 10 gauge power wire from the drivers side battery to the power distribution unit. I thought about extending the wire from the alternator to the driver battery. Any suggestions?

 

[rbattelle]

I don't think that location will give you a reading on charging current. I think you're reading battery output current to the vehicle electrical system. You want to read alternator output current, so you need to move the gauge over to the alternator charging wire.

Ryan

 

[Tinman]

It is reading current draw just fine, but not charge. I was going to do exactly what you suggested, but thought I'd ask b/o the newer trucks being so computer controlled. Like I said, the 01 gauge in the same location reads current drawn and charge just fine. I was going to try extending the alternator wiring to the driver's battery and see what happens. You know, as I write this I remember the grid heater draw doesn't register on the ammeter either. It is on the passenger batt. but with that much draw it ought to be seen. Hummm..... I can see wide fluctuation in current with heater on the 01 and it is on the driver batt.

 

[rbattelle]

I don't think I'm understanding where you've got this thing. If you're measuring the current through the line that powers the main distribution panel, then you're only going to read current that passes through that line, which is the current being used by the vehicle subsystems. Since the grid heaters are not wired through the power distribution block, you won't read current in those lines. And since the alternator is charging the batteries through it's own wire, you won't read that current either.

Of course, it's possible I'm misinterpreting the 2006 wiring scheme.

Ryan

 

[J.BURCHFIELD]

rbattelle, sounds like you know what you are talking about. My needle only moves slightly toward the charge side when I start the truck but soon returns to zero. I hooked it up according to the directions that came with it years ago. what has always made me wonder it is a 60 amp gage but my alternator is rated 120 amps. I would greatly appreciate someone sending me a wiring diagram or telling me what I am seeing is normal. It seems to me the needle would show maybe a 30 amp charge at start up then back down to around 5 or 10 amps. At least that is what I remember from the old cars that came with ammeters. THANKS, Jim -- email address removed --

 

[Tinman]

Ryan, your right about the heater. I wasn't think about it correctly.



I have the shunt between the positive bat. post and the power distribution module. I does show current draw but not charge. The interesting thing is, on the 01 it is wiring the same way and shows current draw and charge. Years ago when I hooked up the 01, I have the grid heaters hooked the the shunt with everything else and when they where on, the needle was pegged at discharge. I had a wiring problem related to that (burned wires at the grid connector) so I moved the grid heater back to the bat. Now when the grid heater turns on, the needle move to about 90 amps of charge. I'll look over the 01 wiring real close and see if there is a difference.



The meter I have is 150 amp.

 

[rbattelle]

Well, I'm certainly no electrical engineer. But think of an ammeter like a flow meter in a water pipe - it will only measure the flow going through the pipe it's mounted in.

Regarding charging current, remember that a 136 amp is probably never going to be charging your batteries with that much current. It would probably overheat and explode the batteries. Batteries have a finite maximum charging rate (based on temperature, I believe), so the alternator is regulated to only produce as much current as the batteries can handle at any given time. My gut tells me that ~30-50 amp charging current is probably all you're going to see at any time, except in cases of extended high-current draw on the batteries (such as operating a winch or lots of off-road lights). Don't quote me on that 30-50 amp number - it's just a guess.

The grid heaters draw upwards of 100 amp (I think) each, so you wouldn't want to be monitoring that circuit unless you've got a super heavy duty ammeter.

Tinman, without really seeing exactly how the '01 electrical system works and how you've got it wired I'm not sure why you were able to read different things there.

Ryan