1.1amp draw on battery while off, not fused, any recommendations where to check next?

[PartyPony]

Hey all,

Greetings from San Diego!

I've owned an '84 Bronco II 2.8L for about a year now and it's been a reasonably well-behaved daily driver and surf/camp truck.

About a month ago, a few issues began:

1st: The fuel pump was leaking fuel. I replaced it and have had no issues since.
2nd: Original radiator sprung a pinhole leak along the seam near the upper radiator hose. I had it repaired, re-cored, and pressure tested at a shop that's been in business 99 years. Flushed coolant before removal and after install. Seems to be fine now.
3rd and current issue: When I stopped daily-driving the truck for the radiator leak, I found the battery fully dead in a week. Unchargeable. I bought a brand new battery. It was dead a week later. It then occurred to me that I've got a parasitic drain. The new battery charged back up so that's what I've got today.

I measured with my multimeter and there is a draw of 1.1amps while the car is off and the key is not in the ignition, and the doors are closed (dome light off, etc.). The 84 BII seems to have one fuse box under the steering column. Despite pulling each fuse with the multimeter hooked up in series, there was never a drop in amps that would indicate which circuit contains my draw. If I'm not mistaken, I've established that the draw is not on a circuit running through the fuse box. I pulled the relays one at a time, jiggled wires, replaced a suspicious section of green wire running to the EEC, and never saw a drop in amps from 1.1ish.

I checked battery voltage at 12.2v, started the truck, and the measured voltage went up to 14.5v. With the engine running, I turned on the radio, lights, wipers, everything and the voltage only dipped to 14.3v. After shutting the car down, the battery measured 12.6v, so I think the alternator is doing its job.

Seems like a reach, but maybe the aftermarket radio is wired incorrectly (seems fairly common), and also not wired to its fuse, which could be why pulling the fuse didn't indicate a drop in amps. I'm kind of at my wit's end with that one. If anyone has some better suggestions to check first before I remove the dash, I'd much appreciate them! I'm a bicycle mechanic, so while I can hold a wrench, I'm fairly green when it comes to both cars and electronics. I'll try to keep up if you keep it accessible. Thanks!

- Pete

 

[JerryC]

SWAG, alternator.

 

[PartyPony]

Thanks for the response, @JerryC.

In the meantime, I tested my unfused radio theory pretty easily by pulling the fuse and seeing if it turned on still – it didn't. So that doesn't hold any water.

You seem sure about it being the alternator. Would you mind sharing some of the thought process with me so I might understand the issue more? Thanks for the guidance!

 

[JerryC]

The alternator is a direct connect the battery, you said pulled all of the fuses.
I'm not sure, SWAG is Swinging Wild A-- Guess

 

[PartyPony]

Ahh gotcha, that one's new to me. Well today I'm going to spend some more time testing with my DMM, maybe replace a few other sections of bad wiring, and see if I can come up with something more to go off.

Side note: after reading about your experience with LED headlights a while back, I bought a set myself. What a significant upgrade in visibility haha. Literally night and day. Mine have a yellow DRL halo that reminds me of the classic yellow glow of the old halogens. Thanks @JerryC. Here's a pic of those from the other day - with a bike that I'm nearly finished doing a full frame-up rebuild on.

 

[Jim Oaks]

Let us know if you see a voltage drop when you disconnect the alternator. I had this problem on my Ford Ranger. Turned out to be a relay for my offroad lights, even though the relay worked perfectly fine.

 

[PartyPony]

Update: I replaced the alternator yesterday and the current flowing when off dropped from 1.18 to .45 amps. Pretty good improvement! I know .45 likely isn't as low as it ought to be, but it seems like it will be within tolerance for a daily driver. I may continue digging for smaller drains after some time off to Bronco to work on my bikes!

Before swapping out alternators, I ran a handful of voltage drop tests on the original unit and all seemed pretty regular – at least to my amateur eye. I also tested the diode on the B+ post to try to learn if maybe a faulty diode was allowing current to flow back to the alternator from the battery and it checked out just fine. I replaced some ground leads around the engine bay as well just for luck. Ultimately, I was pretty stumped and decided that the chance of a $55 alternator ending my trouble was worth the money.

This morning was the first day in a few weeks that I didn't have to hook my battery back up to drive to work!

 

[McWillies]

Have anything plugged into your cig lighter? My 89's cig lighter is a constant 12v (and is on most cars iirc). Also check to make sure your cargo dome light (if the 84 had one) isn't staying on when you close the hatch, that's a pretty common issue on these.

 

[ETnBronc]

PartyPony, I went through much the same deal as you on my 89. A fully charged battery would discharge to the point it would not start 2 days later. Replaced the alternator and all is good now. A bad diode in the alternator apparently caused the drain.