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Date:         Tue, 29 Sep 2009 23:06:20 -0700
Reply-To:     Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject:      Re: No High Beams
Comments: To: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
              reply-type=response

well......... I have a trailer, it's brake lights don't pop fuses on the stock brake light circuit, ( a volvo, not a vanagon, fwiw ) nor is that a common problem.

you don't have 6 volt bulbs in the trailer do you ? ( I doubt it ! , just checking )

well, some might scream, but I bet, IF THERE IS NOT SOMETHING WRONG or WEIRD somewhere, you can run a 16 am fuse on that circuit.

Though I *waould be suspecious* , because just hooking up trailer brake lights to the stock circuit is usally not a problem, far as I know. I'd check things carefully, all wriing carefully. I run a dedicated ground wire for my trailer, even though it will usually ground through the hitch.

do the lights flash extra brightly before the fuse pops ?

----- Original Message ----- From: "Rocket J Squirrel" <camping.elliott@GMAIL.COM> To: <vanagon@GERRY.VANAGON.COM> Sent: Tuesday, September 29, 2009 10:43 PM Subject: Re: No High Beams

> I'm not sure what "mismatched ground levels" means, but the trailer wiring > and the connector wiring in the van are new and clean. > > The facts are these: > > 1. With the trailer connected, and a new stock 8A fuse, the brake lights > flash only very briefly before the fuse pops -- I've done this a few > times, it's what happens. > > 2. If the fuse-poppin' overcurrent were due to a short, the lamps would > not flash at all. > > 3. Since they did light, the current was going through them. > > 4. Since the fuse popped moments afterward, the current was higher that > the 8A rating of the fuse. > > 5. Calculations, courtesy of Hr. Dr. Ohm, give us 7A for four 21W lamps in > parallel. Just short of the fusing current of the stock fuse, so if it was > going to go it would have done so after at least several seconds, not a > bare moment after power had been applied. > > What fits the facts is this: my Inrush Current Theory*: Yes my word you > may well ask what it is, this theory of mine. Well, this theory that I > have -- that is to say, which is mine...is mine. And this theory of mine > is this: four 21W bulbs in parallel will draw anywhere between 36A to 72A > for anywhere between a few tens of milliseconds to a few hundreds of > milliseconds, which is plenty strong enough to fuse a 8A link. But not, > apparently, enough to fuse a 16A link. > > Vanagon content: this is part of a thread that is discussing the safety of > putting on increased loads on the old wiring in our vans. > > ========== > * Yes, the hypothesis, Dear Dr. Feynman. > > -- > 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 9/29/2009 9:11 PM Al Knoll wrote: > >> Hey, you're right, could be an intermittant short. Only happens when you >> hook up the trailer. Mismatched ground levels? Hard to say without >> data. >> >> One small matter that needs clarification. The corrosion of which you >> speak >> in glowing terms actually increases the resistance of the circuit. Since >> it >> is a simple single loop current path and the supply voltage is not >> varying, >> the added resistance actually lowers the loop current. Not likely to >> melt a >> fuse specified for a lower resistance load. The connector junctions will >> heat up and melt but not because of additional current through the loop >> unless of course there is some sort of short to ground making a two loop >> circuit. >> >> However, like Dr. Feynman is noted to say "no matter how elegant the >> hypothesis, or how eloquent it's presentation, if it doesn't agree with >> the >> data, it's wrong" >> >> I don't have the data on the electrical banana but I do have the >> credentials. >> >> Takes a double 'ee' to make a dweeb. >> >> Pensionerd. Geeky Dweeb in thin disguise. >> >> On Tue, Sep 29, 2009 at 6:37 PM, Mike <mbucchino@charter.net> wrote: >> >>> It's not as much about in-rush, start-up current or even continuous >>> current draw in a normal circuit. You could install a slow-blow fuse of >>> the >>> original rating to counter start-up in-rush currents. >>> But, now factor in corroded contacts in the bulb sockets, poor >>> grounding >>> (both common complaints on our older Vanagons), and corrosion that >>> 'wicks' >>> up into the wire strands on the ends (invisible under the insulation), >>> and >>> it all adds up to more total, continuous current draw. This gets the >>> entire >>> circuit warm (even hot!) and will break down insulation and plastic >>> parts >>> over time (remember how our headlight switches melt down even with an >>> all-stock circuit?). >>> You need to do an actual ammeter measurement on the van, not a >>> theoretical >>> mathematical calculation based on book and diagrams. Your circuit is >>> far >>> from new and is now modified from stock. >>> When a conductor shorts to ground, accidentally, anywhere along it's >>> entire length, you now have a wire that'll blow (and WILL glow!) before >>> the >>> higher-rated fuse will blow. As I said, it's not a good scenario, no >>> matter >>> how you like to ratonalize it to yourself. You MUST upgrade the >>> conductor >>> to a larger cross-section to prevent this possibility. Alternatively, >>> you >>> could also add another conductor, in parallel, alongside the existing >>> wire, >>> but I don't like that idea much for a couple of reasons (what if it come >>> apart somewhere?). >>> Also, your wires are not running in "free air", but are cabled in a >>> harness alongside conductors, and thusly, the circuit needs to be >>> 'de-rated' >>> accordingly. This means that your calculations are wrong, so, an >>> engineer, >>> you're not! (neither am I, but I use my 'book-knowledge' and real-world >>> experience to guide me in making decisions to 're-engineer' things >>> sometimes....) Hope I've explained it properly. >>> >>> Mike B. >>> >>> ----- Original Message ----- >>> From: Rocket J Squirrel >>> To: vanagon@GERRY.VANAGON.COM >>> Sent: Tuesday, September 29, 2009 8:58 PM >>> Subject: Re: No High Beams >>> >>> >>> I don't dispute your knowledge and experience. >>> >>> Let's see how closely VW cut things. >>> >>> 97.58 (Bentleys) shows the brake light switches fed by a single 18 >>> gauge >>> wire through a 8A fuse (S8). 18 gauge wire is rated to carry 13 amps, >>> continuous, in free air, forever, if it has insulation rated for 60C. >>> There are insulations rated for higher-temperature operation, and the >>> wire >>> can be run up to 18A or more with better insulation. But I don't know >>> what >>> kind of insulation is used in the Vanagon, so I'll use this rating, the >>> most conservative I could find. >>> >>> The two brake lights on the Vanagon are 21W, so they each draw 1.8A, >>> steady-state, although the turn-on surge of a tungsten filament can >>> exceed >>> the steady-state value by 5 to 10 times because a cold filament has >>> lower >>> DC resistance than a hot one. >>> >>> So the initial turn-on current of the two bulbs together can be >>> anywhere >>> between 18 to 36 amperes, but that surge will be brief - somewhere in >>> the >>> tens to hundreds of milliseconds. Less than a second, anyway. >>> >>> Clearly the steady-state current draw of the two bulbs (3.6A) is well >>> below the 13A current rating of the wire and the 8A fuse. The fuse can >>> handle the brief turn-on surge. >>> >>> When I doubled the load by adding a pair of 21W trailer lights, the >>> fuse >>> blew the moment I stepped on the brakes for the light test. Maybe >>> because >>> the steady-state current (7.2W) exceeded the 8A rating of the fuse -- >>> that's darn close (anyone know the tolerances on these cheap fuses?). >>> More >>> likely, doubling the inrush current to somewhere in the range of 36 to >>> 72 >>> amperes popped the fuse. >>> >>> But doubling the brake light loading doesn't exceed the current >>> carrying >>> capacity of the wire. "Noxious smoke and fumes" are not likely to >>> result >>> from passing 7.2A through wiring rated to 13A @ 60C insulation. The >>> inrush >>> current of the bulbs is too brief to heat a length of wire 12 or more >>> feet >>> long by more than a few degrees. It certainly won't "glow like a >>> lightbulb >>> filament" even if I was passing 16A through it steady-state due to a >>> wiring fault. It would get darn warm and eventually the insulation >>> would >>> fail somewhere. >>> >>> Going from 3.6A to 7.2A in wiring very conservatively rated for 13A is >>> safe enough for me, especially since I only drive with the trailer a >>> few >>> times a year. I reckon the engine will give out before the wiring will. >>> >>> BUT -- Mike B. is right: DO NOT try this at home. Just because I jump >>> off >>> a bridge doesn't mean you should. I do not need a phone call from your >>> widow's lawyer. Never modify any wiring or electrical accessories on >>> your >>> van unless you know what you are doing and are willing to accept the >>> risks >>> of a miscalculation. >>> >>> -- >>> 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 9/29/2009 5:16 PM Mike wrote: >>> >>> > You should NEVER swap up to the next size fuse, when any type of >>> circuit >>> > fault causes the correct size fuse to keep blowing. >>> > The fuse rating is engineered to blow at nearly the maximum >>> > current-carrying capacity of the wire. If you add a greater load to >>> an >>> > existing circuit, and that causes the original size fuse to blow, >>> that >>> > means that the wiring is pulling more amps than the wire size is able >>> to >>> > safely handle. If you proceed to install the next-size-larger fuse, >>> you >>> > now have created a fire hazard that could cause a total loss of your >>> > treasured vehicle. When a wire draws too much current, it gets hot, >>> > melts insulation, the copper can even glow like lightbulb filament >>> along >>> > its entire length! Not good! At this point the wire becomes the >>> > weakest link and 'blows' instead of the fuse! Ii's also capable of >>> > filling the vehicle with noxious smoke and fumes. Do you want to >>> keep >>> > your family in this vehicle? I can't recommend it. >>> > >>> > Mike B. (licensed FAA aircraft mechanic, and licensed electrician in >>> 2 >>> > states) >>> > >>> > ----- Original Message ----- >>> > *From:* Al Knoll <mailto:anasasi@GMAIL.COM> >>> > *To:* vanagon@GERRY.VANAGON.COM >>> <mailto:vanagon@GERRY.VANAGON.COM> >>> > *Sent:* Tuesday, September 29, 2009 7:09 PM >>> > *Subject:* Re: No High Beams >>> > >>> > Actually, Rocket J. you can discern the wire size to the brake >>> lights by >>> > gazing at the current track in the bently. With that in mind you >>> can >>> > estimate the current carrying capacity, then see if the total >>> draw >>> > exceeds >>> > the reasonable capacity of the wire. If it does't then just fuse >>> to >>> the >>> > next higher value. If it does exceed the RCOFTW by some you >>> might >>> > have to >>> > run a second circuit. Works for all accessories of course. >>> > >>> > Pensionerd. >>> > >>> > On Tue, Sep 29, 2009 at 7:20 AM, Rocket J Squirrel < >>> > camping.elliott@gmail.com <mailto:camping.elliott@gmail.com>> >>> wrote: >>> > >>> > > Along those lines, I instantly blew the fuse for the brake >>> light >>> > circuit >>> > > when I connected up my little trailer and tested the lighting. >>> Not a >>> > > miswiring, just the additional load of the trailer's two >>> little >>> brake >>> > > lamps was sufficient to pop the fuse. VW must rate the fuses >>> > pretty close >>> > > to the expected load current so even a non-shorting fault is >>> > sufficient to >>> > > open the fuse. Had to swap up to the next-sized fuse there. >>> > > >>> > > -- >>> > > 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 9/29/2009 4:15 AM Frank Condelli wrote: >>> > > >>> > > In a message dated 28/09/2009 3:14:30 P.M. Eastern Daylight >>> Time, >>> > >> LISTSERV@GERRY.VANAGON.COM >>> <mailto:LISTSERV@GERRY.VANAGON.COM> >>> > writes: >>> > >> >>> > >> If you were to read my _Headlamp Relay Upgrade_ >>> > >> (http://frankcondelli.com/hdltrela.htm) webpage. It >>> > specifically says >>> > >> that it is necessary >>> > >> to change the 10 amp fuses to 15 amp when installing the >>> higher >>> > wattage >>> > >> bulbs. >>> > >> >>> > >> >>> > >> >>> > >> Mark Drillock got it, right on the button. Both fuses 9 >>> and >>> > 10 were >>> > >>>>>>> >>> > >>>>>> blown. >>> > >> I guess those little 10 amp fuses don't like the bigger >>> lamps I >>> > have in >>> > >> both >>> > >> units. And since I drive at night very seldom they could >>> have >>> > been out >>> > >> for >>> > >> some time.<<<<<<<< >>> > >> >>> > >> >>> > >> >>> > >> >>> > >> >>> > >> Cheers, >>> > >> >>> > >> Frank Condelli >>> > >> Almonte, Ontario, Canada >>> > >> '87 Westy & Lionel Trains (_Collection for sale_ >>> > >> (http://frankcondelli.com/trainsal.htm) ) >>> > >> _Frank Condelli & Associates_ >>> > (http://frankcondelli.com/busindex.html) >>> > >> - >>> > >> Vanagon/Vanagon Westfalia Service in the Ottawa Valley >>> > >> _Vanagon Stainless Steel Exhaust Systems_ >>> > >> (http://frankcondelli.com/exhaust.htm) >>> > >> _BusFusion_ (http://www.busfusion.com/) a VW Camper camping >>> event, >>> > >> Almonte, ON, June 11 ~ 14, 2009 >>> > >> >>> > >> >>> >>


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