Heat went out in the 2001 van. low speed blower didn't work, then med, then finally high. Determined it needed a new resistor in the blower housing.

I replaced that and the function switch in the dash as well.


Now it appears something is very quickly draining the battery when I reconnect the battery.


I cant imagine what could be shorted/open, it ran fine this morning when I moved the van to the garage to work on it.

Battery is at 11.8v but drops down to around 7 as soon as I put the cable back on.

I just don't see what could cause the sudden change in the battery usage. I had removed the motor cover to get at the radio. I had to take that out to get at the function switch. I did have it running without the cover, before I swapped the switch and resistor.


Also, I tried to start it with the function switch disconnected. It just clicked. I assumed this was a designed failsafe to prevent starting.


Any other ideas? Could something else have shorted near the battery? Could this be a broken wire or something else that may have occurred near there? What other components are near?

I'm at a loss here!

 

I'll bet you had the doors open and the interior lights on while working on the switch etc.
That is possibly why the battery has been discharged unless you disconnected the battery before starting the job. If it was the interior lights the battery may recover enough overnight to allow starting the truck. Otherwise the battery is tired and needs a charge or to be replaced.

 

I don't think that was it. Lights were off and doors were closed, as I had a small heater going inside the van. There is something draining the battery as soon as I touch the battery cable to the post. It drops from 12v down to 6 or 7 within 10 seconds or so, and will keep dropping if i leave the battery attached. Battery voltage recovers as soon as I pull the cable off.

 

The first question I would like to ask is, do you get any kind of heavy spark/arc when you touch the cable to the battery post ? If so, yes something is on somewhere or maybe a wire is in the wrong place. If you don't get any kind of heavy spark and the voltage just plain drops ,the battery is the problem. A voltmeter reading taken the way you are explaining it is not of very much value. If you were able to connect an amp meter between the battery cable and battery post it should show you how much is being pulled from the battery when you make the connection. Anything that can make the battery voltage drop that much in that short time is capable of doing a welding job and the sparks can lite up your life.
That is why I suspect the battery is discharged or ready for replacement.

 

Yes, there is a spark, but not a very big one, about what I get when jump starting a vehicle. The battery in the van is pretty new, and has never had a problem starting the van, even after sitting for a couple weeks. I really dont think the battery is the problem. At least not yet, I seem to be abusing it at the moment!
Can I try jumping it with another vehicle without reinstalling the battery, or is that going to fry the second battery.

 

The fact that the spark is not a heavy one ,might indicate something is on. If you connect the jumpers from a good vehicle battery to your battery while it is disconnected then start the other vehicle , it should charge your 1st battery some ( about 10 minutes) even enough to get your truck started. If that works for you , the battery didn't hold it's charge and is questionable.
You should be able to connect the jumper cables to your battery cable ends, but they need to be good solid connections and decent jumper cables not flimsy cheap ones.
You will still get the small spark when making the final connection, but the donor vehicle should not be running or have the key on. This is to prevent a voltage spike in the donor vehicle which could cause problems. Then you can try to start your vehicle and if it starts OK , Shut it off and disconnect the cables and have your original battery checked.

Reminder--neither vehicle should have the ign key on at any time when connecting jumper cables !!!

 

I am hesitant to try jumping it with my only remaining vehicle. Since I keep seeing this voltage drop, something else must be happening. So far the battery has been able to recover each time.
Here is what I have done so far, based on recommendations from one of those pay for an answer sites.

Replaced the resistor pack in the blower housing
Replaced the function switch in the dash

I tried putting the old components back, didnt do anything.
swapped the relay under the hood with an ajoining one.

Observed the pigtail for the function switch was slightly deformed/melted, and so believe it may have been shorted at some time, so I replaced the socket and pigtail wires from the function switch back into the wiring harness.

Now, I have all the new components in place, attached battery, tried to start.
This time I did get one quick click, but nothing more, and the battery voltage dropped quickly again.

I know the blower motor itself could be bad, but I don't think that would cause the huge load on the battery. At least not since the van started and ran fine earlier.
Any other ideas?

 

Did you try unplugging the replacement plug you spiced in? If you made an error in connecting the wires for the plug, the circuit is incomplete when you unplug the plug.
the resistor is only active when you turn on the key and have the function switch out of the off position.
If you suspect the blower motor has a problem, just unplug it and that takes the motor out of the circuit. The same applies to the resistor, unplug it. Nothing will work.
Usually if there is a serious electrical short circuit you should blow a fuse that controls the circuit. The way you are using the voltmeter is not right here. All it shows is the available voltage is gone when you make the connection. A good battery will go down a lot slower than what you are describing. If a starter is shorted for example, and you have the voltmeter connected to the battery when you go to start it even with a heavy drain the battery voltage will go down and the terminals will get hot due to the excessive current draw. If the voltage goes down as fast as you describe the battery just doesn't have it to give.