Hello All,
I've just done a 3G upgrade on my 76 Highboy using a P&P sourced alternator. I followed the excellent information and diagrams found in the forums, and all has gone well. I'm getting 14.6 volts at an idle and (almost) everything looks good.
My truck had a lot of "rat nest" wiring when I got it (trailer connections and snowplow) and I have been going through it making repairs. I have come to hate those push on connector taps. I have manufactured a new harness from the left front fender apron connector to everything aft, and I'm still in the process of correcting things behind the dash. Along the way I'm using a multimeter to check voltage and continuity.
Here's my question. Should I get a faint spark when I touch the negative cable connector to the negative battery post with everything turned off? I have traced this apparent current flow through the A terminal of the regulator. I have read that the A terminal is always "hot" as it is the sensing circuit of the regulator. So, is this spark transient artifact of the A circuit "sensing" or is leaving my battery connected going to end up in a drained battery?
I know I could experiment, or use a little elbow grease and cart the alternator into the parts store, but I thought maybe someone here could educate me a bit. I really do like to understand these things.
Anyways, thanks to all who post here. You folks have put together one heck of a knowledge base.

 

This can be normal. It is a function of the ultra-low output impedance of the battery, any capacitance through the system, and any hot-at-all times loads that happened to be connected.

The battery terminal shouldn't be sparking every time you connect it. Maybe just the first time. If it keeps happening within short periods of time, there may be a parasitic load. The regulator could be bad as you suspect (see below), or you could have a door open (which will try to keep the dome light on). Always wear goggles when working around a battery.

The 'A' input of the regulator should not be drawing current with the truck OFF. With the old electromechanical regulators, the 'A' input was physically disconnected internally until the field relay closed. I would imagine that a modern electronic regulator (as would be the case with a 3G) would exhibit a similar high-impedance behavior.

The regulator is not supposed to be something that can drain the battery. It should not be drawing significant amounts of current with the engine OFF and if it is, it's bad.

 

Thanks for the insight fmc400.

I have checked, and I continue to get this faint arcing when touching the negative cable to the battery post that doesn't dissipate with repetition. I decided to charge up the battery since I had been tracing wiring and tested out my pick and pull MK VIII fan find. Those suckers sure do blow!
The battery came off the charger, and settled down @ 12.71 volts. I isolated every other circuit, leaving only the B+ terminal and the yellow wired A terminal connected, and verified that the spark was still there. After sitting about 36 hours, my battery voltage is @ 12.66 volts. I thought: "Well, batteries tend to settle in after a charge, maybe I'm still OK?" At this point, I connected up an improvised continuity tester using an incandescent instrument panel bulb. Across the battery posts, light. Across the disconnected negative post and connector, no light. I just picked up some LED side marker lights for my flatbed (still working on completely rewiring the back end of my truck). When I connected the LED across the negative terminal and negative connector, I did get a faint light from the LED array. So, I do have a very small draw going across there. Right?
I guess I'll pull the alternator and go have it checked out. No biggie, it just looks so good on there, and that 14.60 volts at an idle sure had me jazzed.

 

Set your multimeter to amps, connect the meter leads accordingly (they're usually different for volts/ohms vs. amps), and put the meter in series between the negative battery post and the negative battery cable. If the meter shows the system drawing more than 70 mA with the truck completely shut down and the doors closed, the draw is too much. If the draw is below that, you're fine.

 

its probably your radio memory draw.

 

Yeah mine sparks when I touch the cable to the battery as well. I think it goes to the radio memory as mentioned above.

 

Thanks, you guys.
I don't have an ammeter on my present multimeter, another tool for my wish list. Damn, seems like any project you start on these old trucks will nickle and dime you to death. Presently I'm trying to finish up this firewall-back wire harness "roll your own" project. I think I'll keep an eye on my battery charge for now, everything besides the alternator is isolated out. I'm waiting for my Delta Current Control to arrive for that Mark VIII fan install. After playing with that for a while I'll sort out this alternator. Thanks to all, I'll keep you posted.

 

You'll get there. Be patient and methodical.

Btw, I'd rather put a few bucks to keep my rig going than living with a $400 monthly payment for years and years.

 

you will always have a current draw as previous said. something always wants juice. I just did the three g upgrade and is working great. Now working on my dual battery. lotta late nights. just have to find the right feed for the constant duty solenoid. then how to get a feed for the new volt meter for the second battery, so it doesn't drain the battery. I have the second battery tray, had to modify for these newer batteries. next will be the fuse block install from my wife's tarus to replace the realays for my headlight upgraded and all my stereo and aux lighting. My back is killing me wiring the switches and guages. I keep saying It's my hobbey,but it's a bitch sometimes.....

 

Folks - while radio memory does draw power at all times, it should hardly be any at all. It's only a "sip" to keep an oscillator running. If there is a concern that a truck is drawing too much current while shut off, the only way to gauge this quantitatively is to measure the current with a multimeter.

 

Does your hood have a light bulb underneath it, my 77 does, and so does my 79,,, if your hood is open when doing this, which I am going to ASSume it is, could this be your draw?

 

I agree 100% on spending large payments on something that is depreciating from the minute you sign the papers, plus taxes and full coverage. This truck is just for handy around the place, my hobby and favorite toy. With a few dollars and some sweat equity this truck would be well worth the $4000.00 1976 MSRP again. My wife don't see it though. CLEAN, shiny, an automatic, and something she could climb into and drive would be more acceptable... But that's what makes it Mine! Mine! Mine!
Actually this truck serves another purpose, it can transport me back to growing up in the 60's and 70's running around these back roads, the boy part of my Dad's one man and a boy construction company. I don't know why Dad drove Fords, he wasn't very mechanical, just what he always owned back then. He did buy a new Ford pickup around 73-74, must have been a F100, 6 cylinder, automatic. That A/C sure was sweet, made it hard to climb out and get to work that summer.
Well, I finally got my bed and tail lighting strung up and tested seems to check out OK with just one glitch. The turn signal blinker didn't work in either direction, so I pulled the one out of my other truck. When I went to pull the original, non-working one it was very warm. So, I changed out the flasher and it did not work immediately, but then started flashing at a pace that seems to vary in time interval. I have ran a ground wire that originates at the back attachment screw of the Duraspark module and is the terminating ground for every light assembly. I'm wondering if there might be more impedance going on here than should be, causing the flasher to misbehave. I intend to insert several ground to chassis points on this ground circuit and see if this clears up. A new electronic flasher is on my list so I can end up all LED at completion of this project, I think it might be wise to get all of the bugs out before introducing a $25-30 flasher into the mix.
As for the harness, I've used Cerrowire 16 AWG primary from Home Depot which turns out to be cross-linked polyethyline insulated. I've made mechanical butt connections were the wires cross and wrap around each other, and hit these well with 60/40 solder. I've covered each connection with double shrink wrapping.
Now that everything checks out, I'm gonna wrap my bundled wire in rubber stretch insulating tape and covering this with Scotch 88 vinyl tape before tucking it inside flex tubing. I realize this may be a glommy mess for some poor SOB in 2050, but for me, I hope this mess will be put to bed. Similar to how we did submersible pumps back in the day. Oh, yeah, I did wire in a new connection for my 74, F100 truck bed trailer too.
I've been draining the battery checking lights so I've lost track of voltage drain across the alternator. I'll get back to that soon.
Hey, folks, I do appreciate your support. I better get back to work.

 

I hear ya with working on your truck. All I hear about is garage time till midnight plus.
after work that's my down time.....sort of. we all know how one thing ya want to do turns into an extra couple hours! My garage is my happy place, but the wife doesn't want to her that. I try to get my daughter out away from Facebook and help, cause she will be driving soon. In want her to know what's going on with a vehicle. the list is endless with a old truck. just got new front shocks on tonight. what a difference, a quick coat of spray on the front springs and control arms,axel. looks better.gotta link up some picks.........

 

Hey, Y'all

Sorry to open this can of worms and not stay with it.
I just went downstairs and pulled out my backup 3G from my Pick and Pull excursion (I didn't mention I had a stash before, see how I am).
So, I connected a ground cable to the alternator frame and placed the the alternator B+ terminal cable on the positive battery post. I get no spark when touching the alternator grounded cable to the negative battery post. I then plugged in the connector that has the yellow A terminal. I'm getting the same faint spark (I have to turn the basement lights out to catch it) when I now touch the cable that is grounded to the alternator frame to the negative battery post. The other end of the yellow wire connects to the heavy B+ charge cable, (I soldered this connection into the lug on the alternator side of my Mega fuse and protected it with a 16 gauge fusible link). The green/red wire is isolated on the other side of a pulled fuse, and the white wire, well, we all know where that goes.
In conclusion, both of these alternators are exhibiting the same behavior, not that this means either one is functioning perfectly. I haven't mounted and tested the output of this backup alternator. The upside of this, for me, is that I can take this one in to Oreilly in the AM and have it checked out. I really didn't want to fool with pulling the alternator mounted on the truck, changing the pulley and all. Maybe it is being lazy or obstinate, but I just have a gut feeling this alternator is OK, and it looks soooo good on there.
Thanks, fellow FTE'ers I'm sure we will get to the bottom of this.

 

Hey, Marty

You know it brother, wiring up all of these lights on my flatbed and trailer harness in a way that is neat and that I can feel confident with has been a real cluster cuss. A lot of connections and splices for the tail light and grounding circuits especially. A lot of standing back, scratching my head, thinking and rethinking where i wanted to go and getting there efficiently.
I think I too will conjure up a heavy duty headlight circuit in the near future. The one from LMC Truck looks like it plugs into an existing headlight socket to power the relays. Easy, but not very elegant. I've discovered that both headlight circuit splice at the dimmer switch, splitting and running from there forward, right and left. I'm thinking you could power a relay for high beam and a relay for low beam on each side, forward of the fender connector. Then bring your heavy current right off the battery terminals. Fused, of course. I'm thinking if you loose one relay, the other side would still be lit.
Overkill maybe?
What do you all think?
Am I hijacking my own thread?