| Author |
Message |
Steve Krane (Steve_krane)
Registered Member
Username: Steve_krane
Post Number: 23
Registered: 1-2007
Posted From: 76.176.102.234
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 25, 2007 - 10:23 am: | |
Let the smoke out of the + and - wires going to the headlight switch. The switch apparently failed when I shut off the lights after a few hours of driving. The switch is not original. I think it is a 20A switch. Why didn't the circuit breaker protect the wires? Are they just old and failed? Do you replace them? Test them? They are pretty important if you don't like smoke and possibly fire inside the bus. I told my 4 year old that a wire burned. She said, "it could burn people". |
Bob Wies (Ncbob)
Registered Member
Username: Ncbob
Post Number: 215
Registered: 2-2006
Posted From: 75.200.27.237
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 25, 2007 - 10:38 am: | |
Steve, I found a 50A toggle switch at NAPA for my headlight switch for a reasonable price. True it has a longer bat handle than the usual ones but it's a lot easier to find without looking because I usually flash my lights at oncoming buses...just to say 'Hi'.
NCbob |
Gus Causbie (Gusc)
Registered Member
Username: Gusc
Post Number: 465
Registered: 11-2005
Posted From: 63.97.117.35
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 25, 2007 - 5:37 pm: | |
These switches are very old and corroded from sitting so much.
The switch was probably corroded at the contacts which causes high resistance which becomes an electric heater which makes smoke.
I had a couple of switches on my 4104 fail but luckily they failed open.
They don't carry many amps normally because the HL circuit uses a relay to carry the high amps so you don't need anything larger than 20a or probably even 15a will work ok.
(Message edited by gusc on August 25, 2007) |
Tom Caffrey (Pvcces)
Registered Member
Username: Pvcces
Post Number: 1120
Registered: 5-2001
Posted From: 65.74.67.130
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 25, 2007 - 5:56 pm: | |
Gus, I believe that on our GMs, the headlight switch carries the full lamp current. Our switch is rated 30 amps, IIRC.
We DID burn one up a couple of years ago.
Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska |
Gus Causbie (Gusc)
Registered Member
Username: Gusc
Post Number: 467
Registered: 11-2005
Posted From: 63.97.117.35
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 25, 2007 - 7:09 pm: | |
Tom,
You may be right. I need to check my wiring diagram I guess!!
I probably confused it with my start switch. |
James Stacy (Jimstacy)
Registered Member
Username: Jimstacy
Post Number: 100
Registered: 1-2001
Posted From: 75.40.248.198
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 25, 2007 - 8:03 pm: | |
Watch the current ratings!!!! Many switches have a high current rating on AC (like 20 to 30 amps) but only have a 2 to 5 amp rating on DC. DC arcs more on break of the circuit especially on an inductive load. This can be very hard on contacts. Best to put in a sturdy relay (inductive, but small) to carry the load, and operate it with the dash switch. Switch will last forever. FWIW.
Jim Stacy |
Ed Jewett (Kristinsgrandpa)
Registered Member
Username: Kristinsgrandpa
Post Number: 339
Registered: 2-2003
Posted From: 64.24.208.205
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 25, 2007 - 9:29 pm: | |
Any time you break a DC circuit it produces a high induced current. That pits the contacts on a switch if it is not plated with silver alloy.(DC rated)
Then the next time you turn off the load it does it again only worse this time, etc...etc...
That is the difference in AC and DC rated switches, the AC only rated, non plated, switches burn up much faster causing burned wires, coaches, people, etc.
I've seen the argument on this board, people telling others that it's safe to use an AC only switch on DC. "It will work they say." I disagree.... You can wire your coach with bailing wire and it will work, just tape up the wire where it touches metal. "It will work"
The National Electric Code forbids it and for a reason. Over the years time and time again it has caused damage. If it were safe then the Code would allow it.
Jim Stacy is right "watch your DC amperage ratings on DC circuits.
Ed |
Steve Krane (Steve_krane)
Registered Member
Username: Steve_krane
Post Number: 24
Registered: 1-2007
Posted From: 76.176.102.234
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 26, 2007 - 2:27 pm: | |
Thank you for the information about DC vs AC current ratings. I think I'll replace some others. Marker lights for one. The marker light and headlight switches are at the upper right corner of the dash. I could feel that corner of the dash was noticeably warm even before the switch failed.
But what about the circuit breaker? The reason they are there is to provide a layer of safety for things like failed switches. The 4106 uses thermal breakers which automatically reset. I think the engineers intended for the breaker to protect the wires. Can you test them? Do you just replace them (47 years down the road)? Do you trust them? |
James Stacy (Jimstacy)
Registered Member
Username: Jimstacy
Post Number: 101
Registered: 1-2001
Posted From: 75.41.18.112
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 26, 2007 - 8:44 pm: | |
Steve,
When new, most breaker manufacturers only guarantee them for one cycle! Age doesn't help their performance. Some work for years, many die along the way. They always use an autoreset breaker on headlights for safety, but they all get tired eventually. Some old units trip early; some never trip under any load. I replaced all the old breakers at time of conversion. Not to infer, of course, that all the new ones would be good. Just use your best guess.
Jim Stacy |
Ed Jewett (Kristinsgrandpa)
Registered Member
Username: Kristinsgrandpa
Post Number: 340
Registered: 2-2003
Posted From: 64.24.211.231
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 26, 2007 - 9:11 pm: | |
Steve,
Let me tell you about my experience with load testing circuit breakers.
When I worked at a power house on the Ohio river just east of Cincinnati, I worked with Dayton Power and Light's test department for a couple of years. One of the things we tested were breakers, new breakers going into power panels.
277/480 and 120/240 industrial rated, not entry level like Lowes and HD sells. One box of 20 amp breakers had some that would trip at 15 amps and some would go as high as 35 amps before they would trip.
Do breakers wear out? I don't know. They probably would get weak if anything, tripping prematurely. Which is not much of a safety problem, but can be a PIA.
I do know of one that went bad and kept tripping on a 4905. It was on the headlight ckt. It made my brothers pucker factor go clear off the chart one night.
Good luck
Ed |
Gus Causbie (Gusc)
Registered Member
Username: Gusc
Post Number: 470
Registered: 11-2005
Posted From: 63.97.117.30
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 26, 2007 - 11:19 pm: | |
Steve,
A lot of heat in the switch panel comes from the light bulbs under all the labels, there are about three of them, and from the gage lights. |