Date: Sat, 10 Oct 2009 22:56:53 -0700
Reply-To: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <email@example.com>
From: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Subject: Re: Brake light circuit current with trailer,
WAS: Re: No High Beams
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
It's always been working. I'm sorry I'm so wordy, the point I try to make
often gets lost in the exposition.
The brake lights on the Vanagon work fine. They draw 4 amps when the brake
pedal is depressed.
When the trailer was connected, the 8A brake light fuse (fuse 8, 1984)
popped when I depressed the brake pedal. This happened in August 2008 when
I was ready to leave to Bend, and it happened again a few weeks ago the
first time I hooked up the trailer after the move up here. In both cases I
removed the blown 8A fuse and installed a 16A fuse and all the light
My assumption was that the trailer lights -- tail lights, there are only
two bulbs there -- plus the van's brake lights were too much for a 8A fuse
But I'd forgotten that I had installed a powered 3 to 2 converter in the
engine compartment when I wired up the trailer pigtail. It works: when I
measure the current going through fuse 8 with no trailer connected, I
measure 4 amps. With the trailer connected, there is still only 4 amps. It
pulls power from the battery directly to light the trailer's bulbs without
additional loading on the brake light circuit.
The lamps all work as they should.
The measurements do not show any reason why an 8A fuse would pop but a 16A
fuse would hold when the trailer is connected, because as I noted, adding
the trailer does not add additional loading to the brake light circuit. 4
amps, either way.
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
On 10/10/2009 10:32 PM Scott Daniel - Turbovans wrote:
> maybe in the last line you mean the brake lights, and not the tail
> lights, come on when the brake pedal is pressed.
> so it's working then ?
> ----- Original Message ----- From: "Rocket J Squirrel"
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Saturday, October 10, 2009 10:05 PM
> Subject: Re: Brake light circuit current with trailer, WAS: Re: No High
>> You're right -- it's unclear whether the problem is fixed, or what the
>> problem was that caused the fuses to pop.
>> There are two flavors of 3 to 2 tail light converters: powered and
>> unpowered. Unpowered do the conversion and power the lamps from the same
>> circuits that drive the van's tail lights. Powered converters do the
>> conversion but have a +12 wire to draw trailer lamp lighting current from
>> the battery so the vehicle's lamp circuits don't see the load of the
>> I can tell the converter is working fine because the current through the
>> fuse is 4A when there is no trailer connected, and 4A when the trailer is
>> connected. The tail lights on the trailer do come on when the brake pedal
>> is depressed.*
>> * Or even mildly sad.
>> Mike "Rocket J Squirrel" Elliott
>> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
>> 74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
>> Bend, OR
>> On 10/10/2009 6:17 PM Scott Daniel - Turbovans wrote:
>>> so your problem is still not fixed ?
>>> to me, that's not really quite clear.
>>> and .........re :
>>> "The converter is designed to make
>>> sure that no additional loading is presented to the circuit. "
>>> really ?
>>> I never use them, but my understanding is that they are for converting
>>> from a '3 filament system ' ( vanagon - a separate filament for tail,
>>> turn, and brake )
>>> to a '2 filament system' ( where there is tail, and brake, but brake on
>>> one side turns into turn signal when the turn signal is engaged - a very
>>> dumb system I think, and still, oddly, used in brand new American cars
>>> .........without even amber turn signal lenses even ) ...
>>> but ....
>>> just divies up from 3 to 2, or .........where you are going the other
>>> way ..........from 2 to 3 if there is such a converter.
>>> I would start over.
>>> it could be that you have a bad converting gizmo.
>>> here is what I Actually recommend, which I have done to my utility
>>> trailer and it works dead frickin' perfect.
>>> Get motorcycle amber turn signals.
>>> They are often mounted on a rubber stalk too, so bumping them doesn't
>>> brake them off.
>>> I have mine under the rear of my utility trailer .
>>> this way, I have a nice 3 filament system with amber turn signals on my
>>> and same on my trailer.
>>> And the turn signal and 4 way flasher can handle the load of 3 or even 6
>>> turn signal bulbs all flashing at once.
>>> I think you have a bad converter unit perhaps, or are trying to use it
>>> incorrectly or something along those lines.
>>> I don't trust sealed electronic gizmo's like that very much anyway. If
>>> they work fine ......
>>> but if any doubt, get rid of that thing and wire it to truly match your
>>> Vanagon's system.
>>> then there won't be any balonie about blowing fuses etc.
>>> Find a motorcylce junk yard - used mc turn signal assemblies are cheap I
>>> would imagine.
>>> ----- Original Message ----- From: "Rocket J Squirrel"
>>> To: <vanagon@GERRY.VANAGON.COM>
>>> Sent: Saturday, October 10, 2009 5:45 PM
>>> Subject: Brake light circuit current with trailer, WAS: Re: No High
>>>> A continuation of a side thread.
>>>> On 9/29/09 I opened my big fat yap to comment on a thread in which a
>>>> member said that he was blowing high beam fuses after going to higher
>>>> wattage lamps (see "No High Beams").
>>>> I helpfully added that on my van, fuse #8 (fusebox, 1984) popped
>>>> after applying the brakes when my little trailer was hooked up.
>>>> the 8A fuse to a 16A fuse* fixed the problem.
>>>> I thought that contributing this anecdote to the thread would help
>>>> illustrate how adding more or bigger bulbs to a lighting circuit might
>>>> exceed the current rating of the fuse.
>>>> Ohm's Law says one 21W bulb will draw 1.75A at 12V, and around 1.95A at
>>>> 13.4V (alternator booted). With four 21W bulbs that's nearly 8A, which
>>>> would pretty quickly pop the fuse, although it should have taken a few
>>>> seconds, and not the brief moment that I witnessed. My guess was
>>>> that the
>>>> bulbs' inrush current** was responsible for the fast blow.
>>>> In the thread, a couple list members took me to task for not taking
>>>> current measurements, I was speaking through my backside. So I measured
>>>> the currents:***
>>>> With stock-type brake lights, no trailer: 3.9 amps @ 13.4V (1.95A/bulb
>>>> which is in agreement with the calculated 2A/bulb @ 13.5V.)
>>>> With trailer: Exactly the same. I had forgotten that I had wired in a
>>>> "powered" 3-to-2 tail light converter****
>>>> So. Why the heck did the 8A fuse pop the first time I pressed on the
>>>> pedal once the trailer was connected. The converter is designed to make
>>>> sure that no additional loading is presented to the circuit. And my
>>>> measurements confirm it. I think it's fair to say that if there was a
>>>> momentary short or glitch in the trailer pigtail or wiring, the
>>>> would have had to deal with it, not the dash fuse.
>>>> I should point out that this scenario played out exactly the same way
>>>> in August 2008 when I first hooked up the trailer for my Escape From
>>>> Science is baffled.
>>>> * These GBC "ceramic torpedo" fuses only come in three flavors: 8A,
>>>> 16A, 25A
>>>> ** Inrush current, I felt, was the reason why the fuse was popping so
>>>> quickly since light bulbs will draw 5 to 10 times as much current when
>>>> power is first applied than when they are hot.
>>>> *** My reader will recall that I can't be trusted with an ammeter:
>>>> none of
>>>> my ammeters have intact fuses in them. I've blown them all. To make
>>>> measurements I made a 0.01 ohm (+/-) "resistor" using 19'' of 40-mil
>>>> diameter solid-core copper wire soldered across a blown fuse. By
>>>> the voltage drop across this current-sampling resistance and
>>>> applying I =
>>>> E/R I had my ammeter. Easy as cake.
>>>> **** The trailer has two bulbs, one on right, one on left, Vanagon uses
>>>> four bulbs: right turn, left turn, and two brake lights wired together,
>>>> three circuits total. A converter is needed to drive the two-circuit
>>>> trailer from the three circuit van. A powered converter connects to the
>>>> battery to avoid additional loading on the original lighting circuits.
>>>> Mike "Rocket J Squirrel" Elliott
>>>> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
>>>> 74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
>>>> Bend, OR