We are processing orders and shipping them daily Monday through Friday.
Toll free order line and fax: 888-250-8139

Vangon Articles - How can I find out what is draining my battery?!?!


Search by SKU or Keyword

Vanagain on Facebook!

How can I find out what is draining my battery?!?!

January 28, 2015 5 Comments Electrical Ken Wilford

Testing for Parasitic Power Drain:

Does your VW Van or Westy lose power when it sits for a day or two?

What you want to do is test your electrical system for what is called a Parasitic Battery drain.
When your van battery goes dead overnight, usually either the battery is at the end of its life span, or you left something on, such as a light. Occasionally something is drawing power that’s not of your doing. This is a parasitic draw, and it can cause the same result as leaving the headlights on: a dead battery in the morning.

1. Remove the negative side battery cable from the negative battery terminal.
2. Attach an ammeter(this measures amperage) between the negative cable and the negative battery post. wait a few seconds to several minutes for the car to go into sleep mode. i.e. when you make the contact with the test light the cars computer systems “wake up” after a bit of time they will go to “sleep”.
3. If the ammeter is reading over 25-50 milliamps, something is using too much battery power.
4. Go to the fuse panel(s) and remove fuses, one at a time. Pull the main fuses (higher amp ratings)last. Be sure to observe the ammeter after pulling each fuse.
5. Watch for the ammeter to drop to acceptable drain. The fuse that reduces the drain is the draw. Consult the owners’ manual or service manual to find what circuits are on that fuse.
6. Check each device (circuit) on that fuse. Stop each lamp, heater, etc. to find the drain.
7. Repeat steps 1&2 to test your repair. The ammeter will tell you exact numbers.

Prime suspects that I have found over the years:
1. Fancy Radio/Amps. These have a memory or some type of capacitors, that will drain the battery over the course of a couple weeks of sitting. You can either make a switch to turn off the draining circuit, or install a battery charger so that it will keep the battery up when the van is sitting.
2. Tail lights/crappy trailer wiring. Sometimes the brake light switches will fail and this will keep the brake lights on. This is pretty obvious since you will notice the lights staying on when the van is shut off and sitting. The other thing that can happen is that someone in the distant past (or you) has installed a trailer wiring kit from Wal-mart. Are you really going to tow something with this van, ever? You really shouldn’t. Highly suspect the trailer wiring whenever the van’s electrical system does anything strange. It is always crap! I usually remove it unless the person insists that they really need it.
3. Leaving interior lights on by mistake. That light above the glove box in the Vanagon or the one above the visor for checking your makeup. You left it on you naughty person you!

PS: If you don’t have an ammeter/volt meter you can also use a test light instead. In the directions above just substitute the ammeter with a test light. I usually use a small hose clamp to attach the spike of the test light to the negative battery terminal and the wire end should have an alligator clip on it so you can attach that end to the negative battery cable. If there is a drain the light will light up. Follow the directions above until the light goes out and you should find the drain that way as well. Some folks are very scared of meters, so this is for you if thinking about a volt/ammeter makes you run for the hills ?

Van-Again Copy Right 2015


Ken Wilford October 25, 2016

It could be a problem with your fuse panel itself. There is a large red wire that is feeding the panel directly from the battery. Try unplugging that from the back of the panel and see what happens. Also look at the battery and be sure there isn't another wire tied to the positive terminal that is going somewhere beside the fuse panel. On some 84-86 Wolfsburg Westfalias there is a second battery under the driver's seat that people are unaware of. If that is dead it could be causing a battery drain. Let me know what you find out.

Nirav V. Patel October 19, 2016

84 west // I have gone through these instructions and never saw a drop of +12v after removing fuses one by one. Tonight I pulled the connector from the rear of my ignition switch and pulled a very old stereo unit, to no avail. I'm still getting +12v from the negative terminal to the negative cable. Any idea on next steps?

Eric October 2, 2016

I finally found the problem was the fuel injection (digifant) relay in the engine compartment next to the fuel pump relay.

Ken Wilford July 12, 2016

Re-read the directions. You are only supposed to unhook the ground connection and place the light or meter between the ground wire and the ground battery terminal. Ken

Sammy July 4, 2016

When I put the meter between the terminals, positive (red) on negative battery terminal and and negative (black) on ground cable, a -12.54 shows up on the meter, now what?

Leave a Reply

Want to join the discussion? Feel free to contribute!