Parasitic draw with new Tundra alternator

[EricG]

Hi guys - this past summer I used Photoman's bracket to install a 130A Tundra alternator. I ran a new cable from the alt to the + battery terminal by way of a maxi fuse. Taped up the old cable and left it in place, as described here: https://forum.ih8mud.com/showpost.php?p=7435209&postcount=12

After the install I began experiencing a parasitic draw on the battery - come out after a few days and the battery was dead. I had done a bunch of stuff at the same time as the alternator install, so I didn't necessarily attribute it to that. The parasitic draw may not have started right away either - don't recall exactly. And since I have a dual battery setup, I didn't dig into it right away.

So today I finally went after it. Disconnected the - terminal and found that I'm drawing about 1/3 amp with the key out. Pulled the fuses on various accessories I installed, thinking that would be more likely then the factory wiring. No affect.

Then for grins, I started pulling stuff off the positive terminal. When I removed the new alternator cable, the phantom load disappeared!? Confirmed it by holding the multimeter leads in place while my son touched and removed the alt cable.

So why is my new alternator showing a 1/3 amp draw? I replaced the brushes before I installed it, and had it tested at Advance Auto. It charges fine, gauge works, etc. Could I have messed up the connector wiring (https://forum.ih8mud.com/showpost.php?p=7403436&postcount=4)? Other ideas? Or is this a red herring and my problem still lies elsewhere?

 

[EricG]

Did some googling and came across this thread on another forum - discusses a bad positive diode in the alt as a possible cause - anybody ever sean anything like that? Is it a servicable part on these?

http://forums.anandtech.com/showthread.php?t=2254082

 

[Otamiway]

Eric,

I have not experienced and parasitic draw at all. I doubt it is due to the plug(2nd link).

FWIW..... I did not tape off the original Alternator cable but instead attached it to the Alternator side of the new Fuse(instead of running a new cable to AM 1)

Good luck with your search.

 

[Photoman]

Try to set a multimeter to a small scale AC volts. With the motor running see if the meter reads .5VAC or more between battery positive and battery negative.

Bill

 

[EricG]

Try to set a multimeter to a small scale AC volts. With the motor running see if the meter reads .5VAC or more between battery positive and battery negative.

Bill

So I guess that would tell me something about that diode? I'll try it tonight or tomorrow morning. Thanks.

 

[Photoman]

So I guess that would tell me something about that diode? I'll try it tonight or tomorrow morning. Thanks.

Basically, an alternator makes AC which is rectified to DC with the diode bridge. If a diode is going bad it can leak AC. Here is a picture I did earlier this morning on my 1993 with a 150 amp alternator I just put on. It is better to do the test with the meter positive lead on the alternator "B" terminal and the meter negative lead to ground.

Bill

 

[azTony]

What is that white stuff?

 

[Tapage]

Basically, an alternator makes AC which is rectified to DC with the diode bridge.

pretty nice info Mr. Bill ..

 

[EricG]

Try to set a multimeter to a small scale AC volts. With the motor running see if the meter reads .5VAC or more between battery positive and battery negative.

Bill

Nope - 0.03V

 

[Photoman]

There are circuits still being fed from the new alternator wire, the same as the old stock setup. Try pulling all the fuses and see if the drain stops, not just the new circuits you installed.

Bill

Edit to add picture. Just read the lower right box. These are the circuits that are fed from the battery positive via the alternator "B" post. When the new wire alternator wire is disconnected these circuits are disconnected, so there could be a drain from one of these circuits or another circuit they feed.

 

[EricG]

There are circuits still being fed from the new alternator wire, the same as the old stock setup. Try pulling all the fuses and see if the drain stops, not just the new circuits you installed.

Bill

Edit to add picture. Just read the lower right box. These are the circuits that are fed from the battery positive via the alternator "B" post. When the new wire alternator wire is disconnected these circuits are disconnected, so there could be a drain from one of these circuits or another circuit they feed.

Yea, of course - that should have been obvious to me

Anyway, I've now pulled every fuse in both the under-hood fuse box on the DS fender and the in-cab fuse box by the driver's left knee. The only ones that had an affect were the 50A AM1 fuse itself, and the dome fuse which dropped the load from 0.31A to 0.29A. Also pulled the EFI & horn relays, unplugged my brake controller and pulled the wire from the brake controller auto-reset breaker and pulled the fuses from my battery controller. No change

One thing I did notice is that when I touch the multimeter probe to the battery post & cable I here a very faint hum from somewhere under the hood. Just at the edge of hearing, but if I had to guess I'd say it's coming from either the top of the engine or the DS firewall area. But again, I can barely hear it - if it wasn't for it starting and stopping when I make contact, I wouldn't know it was there. Maybe a relay somewhere? Gonna take one of the kids out and see if younger ears can pinpoint it better.

Open to any suggestions! What is powered through AM1 but doesn't have a fuse in the fender or DS knee fuse boxes? Trying to orient myself to the FSM EWD now...

 

[Photoman]

The fuel pump relay might be located where you are saying? You could try the piece of hose up to the ear trick to try to pin the hum down.
It sounds like you are on to something with that hum business.

Bill

I did not see you mention it but you probably pulled the headlight relay?

 

[EricG]

Pulled the 15A headlights fuses, didn't see the relays. The fuel pump relay occured to me also - I just got a spare one from a part-out but couldn't find it under the hood. Will search some more.

My daughter couldn't hear the hum, so either its psychosomatic, or the old man's ears aren't so bad anyway

 

[turbocruiser]

Eric, I'm just giving out guesses here in the hope it helps but if it isn't relay related (as in head lights, hazard lights, fuel pump, etc) then what about a fan somewhere for something like cb radio, ham radio, regular radio, amplifier, etc.? Depending on how any accessories were wired in, one of them might be permanently pulling voltage. I've seen some crazy weird wiring for stereo systems and other accessories like cb radios and since so much stuff is stuffed into the dash that might sound similar to what you were hearing. Again just as good a guess as I can come up with ( I don't have the EWB unfortunately so I can't really track down that one fuse for you); you have already eliminated almost everything else. Hope you find the culprit as soon as possible.

 

[western flyer]

Back to your second post about a bad diode in the alt itself: on my 69 AMX I had a similar drawdown problem. Turns out is was a bad diode(s) in the alternator. I searched replacing just the diode(s), but ended up just replacing the whole alt. The problem originated when I had a room-mate that hooked up a battery backwards (long-story) and fried the diode(s). In the FSM for the AMX it actually mentioned the diodes in the alt. and reversed polarity problems, and IIRC it had a test for the diodes.

In short, I suggest trying another alternator and/or figuring out a test for the diodes on you current alt.

Merry holidays everyone.

J

 

[EricG]

Well, it's not the fuel pump relay. Warming up a bit, then going out again to try nd locate that hum with some tubing. It's definitely under the hood, not in the cab.

Eric, I'm just giving out guesses here in the hope it helps but if it isn't relay related (as in head lights, hazard lights, fuel pump, etc) then what about a fan somewhere for something like cb radio, ham radio, regular radio, amplifier, etc.? Depending on how any accessories were wired in, one of them might be permanently pulling voltage. I've seen some crazy weird wiring for stereo systems and other accessories like cb radios and since so much stuff is stuffed into the dash that might sound similar to what you were hearing. Again just as good a guess as I can come up with ( I don't have the EWB unfortunately so I can't really track down that one fuse for you); you have already eliminated almost everything else. Hope you find the culprit as soon as possible.

Here's the summary of the aftermarket electrical stuff I've got.

Stereo wiring is pretty stock, and CB draws from the hot wire for the stereo. That stuff hasn't been touched for years and run from the regular accessory power, so pulling fuses should have found it.

The 2M radio, inverter, cooling fan, extra 12V plugs run off a dedicated line which is fused 8" from the battery. Pulled that fuse also.

Slee headlight harness - I've pulled the + leads from the battery post and have pulled the headlight fuses. Still want to find those headlight relays.

Dual battery controller - there are two fuses associated with this, I've pulled both of them. Going to pull the main cable from the primary battery also, but I don't expect anything.

Brake controller - Pulled the wire off of the auto-reset breaker, unplugged the harness from the controller unit.

So, other then the hum I'm kind of at a loss here. I'm going to try pulling the fuse box on the fender and have a look for worn wires or such - it seems like the problem must be between the AM1 fuse and the rest of the fuses. But the hum doesn't seem to come from that area. Need to look at the EWD some more and see if there's anything else that runs from AM1 but doesn't have a fuse??

How confident should I be that the low-range AC test rules out the alternator rectifier issue?

Thanks

 

[EricG]

Back to your second post about a bad diode in the alt itself: on my 69 AMX I had a similar drawdown problem. Turns out is was a bad diode(s) in the alternator. I searched replacing just the diode(s), but ended up just replacing the whole alt. The problem originated when I had a room-mate that hooked up a battery backwards (long-story) and fried the diode(s). In the FSM for the AMX it actually mentioned the diodes in the alt. and reversed polarity problems, and IIRC it had a test for the diodes.

In short, I suggest trying another alternator and/or figuring out a test for the diodes on you current alt.

Merry holidays everyone.

J

Yea, still concerned about this. Stopped at the toyota dealership yesterday and found that the rectifier is not an individually available part. And a new alt is pretty pricey to just swap out - and it's a PITA to get at.

 

[EricG]

Went out with a piece of plastic tubing - it sure sounds like the hum is coming from the alternator.

Thinking this through though ... pulling the alternator cable removes the parasitic load. But pulling the AM1 fuse also removes it. Wouldn't this suggest that the loss must be downstream of the AM1 fuse? If the problem is in the alternator, then pulling that fuse shouldn't have any affect, right?

I did a little looking yesterday and nobody appears to have an alternator in stock locally. Didn't try the boneyards.

 

[86tuning]

Try another alternator, or take this one out to be repaired by an alternator shop

 

[EricG]

Try another alternator, or take this one out to be repaired by an alternator shop

Yea, looks like that's the answer - was hoping it wasn't since it's a PITA to get it out and I've got a road trip coming up.

But I think it's definitely the alternator. I disconnected the alt from the battery, and connected the AM1 circuit to the battery via the original alt. cable. No more hum and no more loss. I suppose I could try a continuity test from the alt. terminal to ground also.