Date: Sat, 10 Oct 2009 22:05:50 -0700
Reply-To: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Subject: Re: Brake light circuit current with trailer,
WAS: Re: No High Beams
In-Reply-To: <016301ca4a10$9ec5dd60$6401a8c0@PROSPERITY>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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 extra
bulbs.
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
KG6RCR
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
> vanagon,
> 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.
> Scott
> www.turbovans.com
>
>
> ----- Original Message ----- From: "Rocket J Squirrel"
> <camping.elliott@GMAIL.COM>
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Saturday, October 10, 2009 5:45 PM
> Subject: Brake light circuit current with trailer, WAS: Re: No High Beams
>
>
>> A continuation of a side thread.
>>
>> On 9/29/09 I opened my big fat yap to comment on a thread in which a list
>> 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 moments
>> after applying the brakes when my little trailer was hooked up. Changing
>> 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:***
>>
>> Results:
>>
>> 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
>> brake
>> 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 converter
>> would have had to deal with it, not the dash fuse.
>>
>> I should point out that this scenario played out exactly the same way
>> back
>> in August 2008 when I first hooked up the trailer for my Escape From
>> SoCal.
>>
>> 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 these
>> measurements I made a 0.01 ohm (+/-) "resistor" using 19'' of 40-mil
>> diameter solid-core copper wire soldered across a blown fuse. By
>> measuring
>> 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
>> KG6RCR
>
>
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