Parasite draw

[vitamin_c95]

Hello,

As title states, I have a battery draw on my 71. I lose about a half a volt every 8 hours my battery stays connected. I've searched this forum for ideas, and YouTube. What I've found is that I have a 1.9 amp draw. I'm just curious if I tested my diodes correctly, as I think that's my problem. Multimeter on diode setting, I put my black lead on the battery connection of alternator, red on case and it shows .535. Hook the red lead to the battery connection with black lead grounded, it's showing 1.9. This is without the battery itself connected. Does this mean my diode have gone bad? Did I do this right?

[Steeveedee]

Could be. Generally, if a hot diode goes bad the alternator will be warm to the touch (from the current running through it), even if the engine hasn't been running. If the engine isn't running and you pull the hot wire off the back of the alternator, it should not spark, and no voltage should be present between the wire and the post on the alternator.

[rpmerf]

Do you have a generator and voltage regulator, or has it been converted to an internally regulated alternator?

Is there any non factory wiring? Alternator, HEI, gauges, radio, lights?

Here is what I would do. Disconnect the battery. Go to the driver's side junction. Remove the alternator or generator and voltage regulator wires. The only things connected should be the shunt (big wire to the battery), the red wire running in the cab, and the ammeter wire. Test the draw from the battery again. If the draw has dropped to an acceptable level, the issue is the alternator, generator, or voltage regulator. If it is still high, the problem is in the cab. Start removing fuses one by one to see if one drops the draw. If none of the fuses drop the draw, move to items that do not go through the fuse block. According to the schematic, the power wire that comes into the cab splits into 4 places: fuse block, ignition switch, horn relay, and headlight switch. You can pull the connector at the back of each of these 3 items to see if the draw drops.

http://outintheshop.com/faq/wiring/w...s/image002.jpg

http://outintheshop.com/faq/wiring/w...s/image003.jpg

[vitamin_c95]

I'll recheck with this idea. When I checked from my memory, I had my meter hooked between the neg cable and battery. The draw disappeared when I unhooked the regulator in the core support. I was unsure of my findings so when to here and YouTube to check diodes and symtoms. I was never good at electrical work

[rpmerf]

I did have a similar issue with a voltage regulator. Go out to the truck and the battery is dead. 1+ amp draw. Unhook the regulator and the draw was gone. I opted for a 12SI alternator conversion. If i remember correctly, the alternator was about the same price as a new voltage regulator.

Voltage Regulator - $51.79 - https://www.rockauto.com/en/moreinfo...31690&jsn=1093

12SI 78 AMP 9:00 w/ internal regulator - $54.79 - https://www.rockauto.com/en/moreinfo...21891&jsn=1255

Another option might be to open up the regulator and see if there is anything that looks obviously off inside. I had 2 regulators fail on me. The first one I opened up. One of the components let the magic smoke out.

[andrewpclayton]

Ugh i know the frustration of this one... i chased a draw for weeks, and turns out mine was really easy as i was turning the key all the way to the left before removing it. Good luck