84 Vanagon Parasitic Draw

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sped372
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84 Vanagon Parasitic Draw

Post by sped372 » Mon Mar 14, 2016 7:18 pm

Spring has arrived and I'm getting a few minutes here and there to take care of a few issues on the 'new' camper. Before storing it last fall, I noticed I have a 35mA draw while parked that goes away if I pull fuse number 8... [books says dome lights, cig lighter, and stoplights.

I checked the interior lights and cigar lighter wiring for for strangeness or corrosion but found none. Removed suspicious trailer wiring splices but no change. Stereo is on a different circuit, already checked that. I disconnected the harness from the back of the stereo with no effect anyway, just to be sure.

I dropped the fusebox and everything near fuse #8 looks stock, the wire colors match the diagram in Bentley. One fused spade has a smaller red wire, and the other spade has two wires joined to the same spade. I pulled the smaller red wire, which feeds the dome lights, and it did not affect the draw. So, I've at least narrowed it to the remaining circuits... the cig lighter and what appears to be the brake light switches? Unless someone previously tapped into one of those someplace downstream.

Anyone else have any bright ideas? Otherwise I'll just have to keep trying to isolate it!
1971 Karmann Ghia - 1600 DP
1984 Westfalia - 1.9 WBX

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energyturtle
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Re: 84 Vanagon Parasitic Draw

Post by energyturtle » Mon Mar 14, 2016 7:45 pm

Man, I think your on the right track. I bet there's a splice in the cig lighter somewhere? Take the brake light fuse out, and check draw? Was this all at once, or intermittent? What was changed before it was stored? I'm curious, and will be waiting to here the verdict. Best of luck to you.

Scottie

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sped372
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Re: 84 Vanagon Parasitic Draw

Post by sped372 » Mon Mar 14, 2016 8:13 pm

Thanks, just bought the vehicle last fall, going through everything to prepare for this camping season. Guessing it has been that way for a long time, obviously I pulled the battery for storage.
1971 Karmann Ghia - 1600 DP
1984 Westfalia - 1.9 WBX

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sped372
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Re: 84 Vanagon Parasitic Draw

Post by sped372 » Tue Mar 15, 2016 9:53 am

I'm at work but thoughts are circulating in the back of my mind. Could something like a brake light pressure switch 'leak' slightly, allowing a tiny amount of current to pass even when the switch is off? It seems possible but you'd think it wouldn't be so very consistent in the number of mA leaking.
1971 Karmann Ghia - 1600 DP
1984 Westfalia - 1.9 WBX

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Amskeptic
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Re: 84 Vanagon Parasitic Draw

Post by Amskeptic » Thu Mar 17, 2016 8:05 am

sped372 wrote:I'm at work but thoughts are circulating in the back of my mind. Could something like a brake light pressure switch 'leak' slightly, allowing a tiny amount of current to pass even when the switch is off? It seems possible but you'd think it wouldn't be so very consistent in the number of mA leaking.
Alternator diodes are the usual culprit, after the clock/radio/stereo rig has been discounted.

Remove every single fuse and check battery (-) for slight sparkishness. If slight sparkishness is evident, unplug voltage regulator. Sparkishness gone? Excitor diodes. Remove alternator B+. Sparkishness gone? Main diodes.

I ran the Road Warrior for ten years with just removing the negative terminal from the battery until I got around to replacing the alternator.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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sped372
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Re: 84 Vanagon Parasitic Draw

Post by sped372 » Thu Mar 17, 2016 9:13 am

So it would just be leaking back through fuse #8 b/c that circuit is always hot (therefore clear to the alternator when the ignition is off)? Interesting. If this wasn't a camper (and if the Vanagon battery wasn't inconveniently located) I wouldn't be as concerned about it. I "need" to keep the battery connected for the interior light while camping, but don't want to worry about it going dead by the end of a camping trip due to constant leakage.
1971 Karmann Ghia - 1600 DP
1984 Westfalia - 1.9 WBX

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sped372
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Re: 84 Vanagon Parasitic Draw

Post by sped372 » Sun Mar 20, 2016 1:57 pm

I'm not giving up on my leaky brake switch theory just yet... I pulled the tail light housings since it was easy to peek in there, hoping for something obvious. Found a mangled turn signal bulb, which was good to find but obviously had no effect on my phantom draw. I did note, however, that pulling *both* stop light bulbs (left and right) drops my ignition-off current to 15mA. Either bulb installed and I'm back up to 32mA. Pull fuse #8 and I'm down to 6mA... it's all very repeatable. Didn't have time but I think my next check is to pull wires from the pressure switches...

Colin, rethinking this, it wouldn't be isolated to fuse #8 if it was alternator diodes, unless I'm missing something... right? I didn't pull all the fuses and run your check yet, but logically I can't see how it pans out if the current draw is isolated to one fused circuit.
1971 Karmann Ghia - 1600 DP
1984 Westfalia - 1.9 WBX

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sped372
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Re: 84 Vanagon Parasitic Draw

Post by sped372 » Mon Mar 21, 2016 11:10 am

Aha! Pulled the instrument cluster and lookey there, splices on the wires near one of the brake light switches. Where do they go? To the cruise control module. What happens if I disconnect the one on the 'always hot' red and yellow wire? My parasitic load drops to 4mA... so, at least I know the cause. Need more time to dig into the cruise, can't imagine it draws main power from that wire but is likely monitoring brake usage to cut itself out if you use the pedal. A minor victory nontheless! Worst case I can live without cruise and not have a dead battery after a week of camping!

Image

Image

I'm going to attribute my remaining 5 or so mA to the alternator like Colin described. I'll have to run the 'pull all fuses' test to check. I can live with that sort of phantom draw though.
1971 Karmann Ghia - 1600 DP
1984 Westfalia - 1.9 WBX

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Re: 84 Vanagon Parasitic Draw

Post by ainokea » Mon Mar 21, 2016 5:49 pm

You found part of the problem and that's great, but have you checked the ECU for some of that draw? I mention it because no one else has. Ainokea

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Re: 84 Vanagon Parasitic Draw

Post by cegammel » Mon Mar 21, 2016 6:02 pm

I never got around to a full diagnosis on my own voltage vampire, but an onboard battery charger plugged into the hidden outlet under the sink eliminates the fear factor. I plug in at night at home, and when possible camping. Battery is hot in the morning, and I don't have to worry about it. Also, leaving the charger hooked up gives me a little more oomph when starting on cold mornings...probably not best for the charger...

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sped372
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Re: 84 Vanagon Parasitic Draw

Post by sped372 » Mon Mar 21, 2016 8:14 pm

So a little more sleuthing reveals the following:

Cruise module has its own inline fuse tapped to hot side of fuse box. Removing this fuse does not affect parasitic load. Only disconnecting the line to the brake switch solved it.

Additionally, the remaining 5ish mA is mainly for radio presets on the aftermarket stereo. Pulling the fuse to the stereo netted me <1mA draw remaining once the cruise is disconnected. At least it all makes sense now. Guessing there are leaky diodes in the cruise module.
1971 Karmann Ghia - 1600 DP
1984 Westfalia - 1.9 WBX

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Re: 84 Vanagon Parasitic Draw

Post by ainokea » Tue Mar 22, 2016 1:45 pm

If the stereos memory is connected, that might also be a source of draw. Try connecting memory, yellow wire, to the red power in wire, You'll lose presets as the memory won't work until the unit is turned on. I've seen situations where stereo memory goes bozo and kills a battery overnite. Ainokea

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Amskeptic
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Re: 84 Vanagon Parasitic Draw

Post by Amskeptic » Tue Mar 22, 2016 7:37 pm

sped372 wrote:What happens if I disconnect the one on the 'always hot' red and yellow wire? My parasitic load drops to 4mA...
Do Vanagon brake lights go on with ignition "off"?

Earlier VWs, as you know, have ignition-switched brake lights.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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sped372
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Re: 84 Vanagon Parasitic Draw

Post by sped372 » Wed Mar 23, 2016 5:39 am

Amskeptic wrote: Do Vanagon brake lights go on with ignition "off"?
Colin
Yes, (at least I can confirm this for '84) I'm guessing/wondering if this was probably some federal mandate at some point? I can understand the logic, there could be certain scenarios where your ignition cuts out but you would still like to communicate to those behind you that you are on the brakes. Fuse #8 is always hot and has the dome lights, cig lighter, and brake light circuit on it.

I'm going to pop the cover on the cruise module but doubt there will be much to be learned. Most likely I'll just end up leaving it disconnected. It is definitely isolated to the circuit that is 'monitoring' the brake light switch, the cruise module is allowing a little current to bleed around the pressure switch since it is connected to both legs. It's completely independent from the main power to the module or it's main ground. You can disconnect either of those without affecting the parasitic draw. I'm only documenting all of this in case it helps someone else in the future.
1971 Karmann Ghia - 1600 DP
1984 Westfalia - 1.9 WBX

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Amskeptic
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Re: 84 Vanagon Parasitic Draw

Post by Amskeptic » Wed Mar 23, 2016 6:21 pm

sped372 wrote:
Amskeptic wrote: Do Vanagon brake lights go on with ignition "off"?
Colin
Yes,

I'm going to pop the cover on the cruise module but doubt there will be much to be learned.
Where is it located? I didn't think much was going to present itself to me when my 1989 GL idle stabilizer failed and stalled the engine every time I hit full lock or the A/C switched on.

Turns out that the idle stabilizer module was located at the right rear tail light and had ingested some water from the scoop. Cleaned it, re-soldered a connection, idle stabilizer worked fine for the rest of the time I had the car.
Colin
(shouldn't have sold it, I cudda done the dreaded head gaskets easily, but it was 1992 and I did not have the internet)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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