Batteries drained to dead, what is nominal drain on truck?

[BobsYourUncle]

18 days into a 3 week holiday, things were mostly well until this morning, sigh, here we go again....

Parked the truck at the campsite day before yesterday afternoon. Didn't run it yesterday. Went to head out this morning and the truck wouldn't start, batteries were dead. Enough juice to make the solenoid click a bit, that's all.

What the heck? Feb 4 this year, 2 new batteries, March 8, new alternator.

When I tried to start it I had a weird smell come out the AC/heat ducts. Not quite a burnt electrical smell but similar.

I'm baffled here. Thing was running fine until this.

Pulled the negative terminals, put on an ammeter, looked at readout. Started at 1.67A, bled down to about .11A and stayed there.

Left the batteries disconnected for about 7-8 minutes, hooked them up and ran jumper cables to my TT house batteries. Gave it a couple hours for the converter to charge them a bit.

Got it started, ran it a few minutes, alternator got hot rather fast, but it's working so I get that.

Took it for a run for about a half hour, seems to be ok now. Except that weird smell...

It's been a couple hours shut off now, going to go back out, pull the negs and do the ammeter test again.

My question regarding all this:

What is the nominal draw in amps that should I be reading? That is, the normal amount of parasitic drain? Milliamps I guess, not amps.

(TV in sig)

[MEXICOWANDERER]

A well-designed coach or vessel has a fire extinguisher right next to the battery switch next to the door.

[BobsYourUncle]

LittleBill wrote:
generally fan speed resistors are only used for the lower speeds, they are bypassed at High Speed.. GL

As true as this is, they do short out sometimes. Heat caused by resistance increasing from a failing connection gets the pigtail plug very hot until something starts to melt.

Last time this happened the plug end was a melted mess.

We are into a long weekend so I have 3 days off. Going to pull it apart and have a look.

[LittleBill]

generally fan speed resistors are only used for the lower speeds, they are bypassed at High Speed.. GL

[BobsYourUncle]

Update:

I made it home Sunday with no further problems.
Discovered the high speed quit working on my fan motor.

I am almost 100% certain that the fan speed resistor is the culprit.

Had this happen about 8 or so years ago. Driving, suddenly the cab filled up with smoke. Thought it was on fire, I hit the shoulder, nailed the brakes and actually bailed and ran a safe distance away. Wasn't on fire, so I started it up and drove away. Fan resistor had shorted out and melted the wire terminal block, causing the smoke and smell.

Same smell, I recognize it.

My theory is it shorted out just before shutting the thing off. Sitting overnight, it somehow drained the batteries. Not sure but I think the power to the resistor block is hot at all times.

Haven't got in there yet to check it, but will this weekend.

I think GM had a TSB on this issue some time ago.

[Harvey51]

Our 2018 Highlander SUV drew 500 mA when we brought it home in winter. Toyota mechanic said that was normal. Then I discovered that turning the headlights off instead of auto reduced it to 250. In the spring it went down to 100 mA. Any ideas why so much, other than Toyota has too many engineers working on features that use electricity? I put a battery post disconnect on it in case it goes high again in winter.

[JiminDenver]

Thanks! It's great to see you too. In fact I am happy to see most of the regulars are still here helping anyone and everyone that needs it. I hit the road 1/1/17 and haven't had much time to play on line since.

I have to agree about the Eco-Worthy 20 amp. It's been out 7 years and it is still a easy to set up, easy to use, inexpensive solution to a small system. They are only $69 now and still hard to beat for the money. A while back I installed a Eco-Worthy 40 amp MPPT with blue tooth for a customer. It's under $100 too.

The last time I used a Eco-Worthy 20 amp was for a video showing the difference in output between MPPT and PWM. It and a Solar30 each had matching 200 watt portables and the difference is over 3 amps which shows even a small system benefits from MPPT.

[BFL13]

JiminDenver wrote:
Bob, get a DC clamp meter. So much easier.

I wonder if the smell is a a ventilation door actuator that gets stuck on and resets itself once the battery goes dead. I would not think it would happen with the key off but who knows. It certainly sounds like a electrical part is hot but not burning.

There is a blast from the past! Good to know you are still in the game. 🙂

BTW my Eco-Worthy is still slaving away, doing a good job on my 275w panel. That was good advice you gave back then.

[BobsYourUncle]

Thanks for the help guys. 🙂
Truck seems ok at the moment.
Drove around today with multiple start stops.
Long as I can get it home Sunday without it happening again.
Easier to do the slow painful trial and error find the culprit process at home where I have access to all my tools and such.

[steved28]

theoldwizard1 wrote:

JiminDenver wrote:
Bob, get a DC clamp meter. So much easier.

Clamp meters are not always accurate below 1A. Not sure if 0.1A (100mA) would register on some.

Still, should be standard equipment for every RV'er who knows about current. I use mine all the time.

[theoldwizard1]

JiminDenver wrote:
Bob, get a DC clamp meter. So much easier.

Clamp meters are not always accurate below 1A. Not sure if 0.1A (100mA) would register on some.

[theoldwizard1]

BobsYourUncle wrote:
Pulled the negative terminals, put on an ammeter, looked at readout. Started at 1.67A, bled down to about .11A and stayed there.

Under 250mA (0.25A) is typical. As you said, it might take 5 minutes for all of the electronics to go to sleep.

Some electronics occasionally (once every 10 to 60 minutes) "wake up" to check things, but they go back to sleep.

[BobsYourUncle]

JiminDenver wrote:
Bob, get a DC clamp meter. So much easier.

I wonder if the smell is a a ventilation door actuator that gets stuck on and resets itself once the battery goes dead. I would not think it would happen with the key off but who knows. It certainly sounds like a electrical part is hot but not burning.

Yes, the DC clamp meter. It was actually on my list of things to buy before leaving on the trip. Never did get it, so had to use my old multimeter..

Agree with the something got hot. Trying to determine what is the hard part. Something stuck on, causing a hard drain on the batteries. Smell in the AC vents is the only clue I have.
Years ago I had the cab fill up with a similar smell and smoke. So bad I actually pulled over on the highway and bailed, thinking I was on fire. Turned out to be the fan speed control on the heater box. Apparently there was a recall on it years ago. I put a new one on and all was well.

I've checked everything, it all works.

[joebedford]

BobsYourUncle wrote:

joebedford wrote:
If you're using the truck's wifi, that will flatten the battery overnight. Ask me how I know (twice).

Trucks wifi? Not in 2007! 🙂

Sorry. Mine's a 2011. And the wifi was a free retrofit when they dropped 2G coverage in Canada.

[jkwilson]

Have you checked electrolyte levels?