65 F100 with round speedo and 2" round amp gauge on one side, and a 2" round oil pressure gauge on the other. Don't have the amp gauge wired up, just sets there. Thought if I would check to see if any members have found an aftermarket harness, can't have one made up, not sure what circuit consist of. It would be the least expensive route to go. Never have been enthusiastic about wiring it up to begin for fear of toasting the dash harness. Checked with couple of Performance auto suppliers who carry the amp gauge but don't sell the harness separate. Considered replacing with another gauge. Not sure which gauge would be most useful. Perhaps tach, but then it would seem one could go blind trying to keep trac of rpm on 2" gauge. There the vacuum gauge, but then again, not sure what I would be looking for, think want to keep needle between 18-22 in" of vac., can see an accident in the making. What a dilemma, any suggestions, or source would be appreciated.


dave

 

This is easy; I just added an amp gauge, factory, just like you describe but with the sweep speedometer, to my Sweet Southern Comfort.
1. Install an INSULATED stud on the fender apron near the alternator. I used one from an old bus.

2. Disconnect the main BAT harness from the back of the alternator, and connect it to this stud.

3. You will need a 2 - wire heavy duty harness for this part. (I have one extra that needs one of the large ALT connectors, contact me off line if you want it; it came out of a camper special.) Run the two wires to the back of the dash, connect the 2 small eyes to the studs on the back of the ALT gauge. MAKE sure they do not touch, nor that they ground out.

4. Connect one large eye on the other end of the wires to the insulated stud so that it makes electrical contact with the wire that used to sit on the BAT terminal of the alternator. Connect the other large eye to the BAT post of the alternator.

That's it.

Of course, you can do this using heavy duty wire; probably 10 GA will work.

 

Banjo, read your thread and got me thinking. Went out and started looking thru boxes of extra parts and came across 2 or 3 wires, one may be 1 leg of an amp harness. During infancy stage of my salvage parts shopping days would remove items had no idea what they were for but felt may come in handy. One of the wires I came across is a heavy ga wire (blk/wht tracer) with large and small connectors on each end. There is also what appears to be a 2 peg 25 amp junction block on one end, not sure, I may have attach junction block as not to loose it. Looks like it will reach from instrument to fender apron and has a firewall plug incorporated in the wire. Came across another heavy ga wire (blk/yellow tracer) with large connector on 1 end and female plug type connector on the other. Looks like it will reach from instrument to alt. If read thread correctly, appears all I need to do is replace female connector with loop type and walla have the harness. Not sure why I could not use this junction block as an insulator, one side of block says 12v and the other 25 amps. Also, replaced all the harnesses in engine compartment. May look at splicing the fused wire from the old alt. harness for extra protection. Will have to think about it, not sure want a splice in the circuit, and perhaps over kill. Rambling on here, it's what happens with my second, perhaps third cup of coffee. Really appreciate the input Banjo

dave

 

my wiring seems to be a little different, mine has alternator wire going to the insulated block, second large black wire going from block to the gauge, other wire from gauge goes back to the positive side of solenoid...

 

Hiball, that works just as well. Maybe even better, since the correct wires on on the alternator.
The point is that the AMP gauge is in series with the alternator output with respect to the batttery.
The one part you do NOT want in the AMP gauge circuit is the starter. It will draw more amps than the gauge can handle, and will burn it out.
Besides, you don't need to monitor the starter; you know it is drawing current , and whether or not the battery is charged for it to work the moment you hit the key.

 

I guess you could wire it either way, I was just making note that this is how my truck came from the factory or dealer installed!!!

 

Actually, there was a factory installed and a dealer installed version.
The factory version had the oil and water temperature gauge wires and connectors incorporated into a single harness. The harness also included the bulb socket for lighting the gauge. (There may have been more wrapped into the single harness, that's all I remember.)
The dealer version used a single set of 2 heavy duty wires to put the amp in series with the alternator. No other wires were part of that harness.

 

Sorry, seems making extra work. Curious if insulated block is 1 or 2 post. Appears the variation relates to 1 of the wires coming off the instrument, either goes to 'batt' terminal at alternator, or to the starter relay. In the case where wire goes to the starter relay, is there a wire that connects to the 'batt' terminal on alternator. Also, wonder if 2 post, what wire color codes are for the additional wires. I will hold while you run out and check. Appreciate the input.

dave

 

I guess mine is the dealer installed version from what Banjo described, just two large #10 wires from the gauge, one goes to the junction block (only has one post), the other to the Batt/pos side of the soleniod, the other wire to the junction block comes from the alternator harness

 

I have harvested from 2 amp gauge equipped trucks, and both had insulators which crumbled upon removal. As I remember, there was a single stud on both, and both were held to the innder fender with a self tapping screw.

 

my insulator crumbled years ago, I just but a bolt and nut through the 2 wire ends and taped it up...LOL, its been that way since about 1980

 

I found some real nice buss bar insulators for some 480 volt panels works real well for a new post when my old one crumbled.

Jon

 

speaking of amp gauges.....mine looks like I tach when I have it hooked up. I mean it swings worse then my palomar 6 tube palomar linear amp did on sideband...lol

Iv not ever seen one swing like that. Is that how the old alternators and amp gauges do?
I know they somewhat work on "the given draw opposing the battery up and down charge" and the amount of input vs output in a balancing act thus showing only the difference from the battery and alt current flow. lol but should it swing that much? possible causes? Battery weak, alt only charging at higher rpm's? what you think

 

Think will see if can find a fused junction block. Assume the circuit would exceed the 25 amp block I salvaged. Seems electric automotive supplier should have something simular with higher amp capacity. Will kinda puts my concerns to rest with high amps to instrument cluster. Seems if circuit was fused may save instrument, and most importantly the darling truck from becoming toast. Can't visualize the circuit using the starter relay, so will go with wire from gauge to insulator, or fused junction block, and the other wire to alternator. Appreciate input, couple other projects, should have hooked up next few days.

thnx
dave

 

Dave, if you send me your email add I can send you a picture of the circut