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| [GMCnet] Electrical Problem, Turning on Head Lights blows 3 fuses - dash and exterior lights (head l [message #89958] |
Sat, 26 June 2010 01:02  |
J MASSEY
Messages: 4
Registered: June 2010
Karma: 0
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Junior Member |
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Iıve been off the gmclist for over 3 years. Being retired keeps you busy.
About to make a trip to Texas to wrap up storm damage repairs on the family
home
Thatıs taken two years to work thru since I can get loose only for a short
period in the Summer.
Coming home from a rally, I lost lights when it started getting dark.
Turning on Head Lights blew 3 fuses - dash and exterior lights
(head lights themselves are ok). I got home just after the sun set.
Repeated the problem several times with new fuses. Looking at the MHıs
wiring diagram, I suspect a bad headlight switch.
Browsing located the GMC Motorhome Photo Archive and some searching
stumbled across jharpers ³Headlight switch removal/replacement (How to)²
Photo Essay from 2004. Wonderful.
Is there a check of the switch I can make that can exclude it as the cause
of a short in the system without pulling the switch?
The wealth of information this community has assembled over the years
continues to amaze me.
Thanks,
JohnM
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| Re: [GMCnet] Electrical Problem, Turning on Head Lights blows 3 fuses - dash and exterior lights (he [message #89959 is a reply to message #89958] |
Sat, 26 June 2010 01:45  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| J MASSEY wrote on Sat, 26 June 2010 01:02 |
Iıve been off the gmclist for over 3 years. Being retired keeps you busy.
About to make a trip to Texas to wrap up storm damage repairs on the family
home
Thatıs taken two years to work thru since I can get loose only for a short
period in the Summer.
Coming home from a rally, I lost lights when it started getting dark.
Turning on Head Lights blew 3 fuses - dash and exterior lights
(head lights themselves are ok). I got home just after the sun set.
Repeated the problem several times with new fuses. Looking at the MHıs
wiring diagram, I suspect a bad headlight switch.
Browsing located the GMC Motorhome Photo Archive and some searching
stumbled across jharpers ³Headlight switch removal/replacement (How to)²
Photo Essay from 2004. Wonderful.
Is there a check of the switch I can make that can exclude it as the cause
of a short in the system without pulling the switch?
The wealth of information this community has assembled over the years
continues to amaze me.
Thanks,
JohnM
|
John I think you are saying that you blew the same fuse three times. If so, I would go looking for the short that caused the the fuse ti blow. I do not have the GMC wiring diagram on the shared use computer I am using right now to look at, so I can not tell you exactly what lights are on that fuse. I would start by looking at all of the exterior lights since they tend to get water in them and rust or corrode. Open each light and remove the bulb. Clean up the socket and the bulb bulb where necessary. Then turn on the headliight switch without the bulbs installed and see if the fuse still blows.
I do not know without the diagram if the parking and tail lights are on that same fuse. If they are, remove and clean them also.
A small word of warning. Many of the clearance lights are wired backwards. It does not hurt anything since they are mounte din fiberglass except that the bases of the bulbs are hot (+12 volts) rather than grounded. I have one like that and it is mounted very close to the awning. On day I was up there with a screwdriver working with the lights turned on and accidentally grounded the base to the adjacent awning blowing the fuse.
Good luck. I wish I could tell you more but I don't have the wiring diagrams in front of me right now.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Electrical Problem, Turning on Head Lights blows 3 fuses - dash and exterior lights (he [message #89966 is a reply to message #89958] |
Sat, 26 June 2010 02:16 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| J MASSEY wrote on Sat, 26 June 2010 01:02 |
Coming home from a rally, I lost lights when it started getting dark.
Turning on Head Lights blew 3 fuses - dash and exterior lights
(head lights themselves are ok). I got home just after the sun set.
Repeated the problem several times with new fuses. Looking at the MHıs
wiring diagram, I suspect a bad headlight switch.
Is there a check of the switch I can make that can exclude it as the cause
of a short in the system without pulling the switch?
Thanks,
JohnM
|
What year coach do you have. I'm looking at a 73/74 diagram and I see two fuses associated with the lights. There is a 20A for "tail & dome" and a 4A for "panel lights". The 4A is actually down stream from the 20A after going through the panel light dimming resistor. You mention 3 fuses, what is the third? Actually what is the labeling on the 3 fuses you blew. Based on what I can see so far if you are just blowing the 20A dome & tail light and the 4A panel then the problem does not appear to be in the headlight switch.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] Electrical Problem, Turning on Head Lights blows 3 fuses - dash and exterior lights (he [message #90219 is a reply to message #89958] |
Sun, 27 June 2010 22:48 |
J MASSEY
Messages: 4
Registered: June 2010
Karma: 0
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Junior Member |
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Thanks for the response Steve,
Well, I just checked the chassis fuse block and using the terminology from
diagram in my 1977 Transmode Operating Manual (page 64),
The Hazard Warning Light, Stop Light (SFE-20) fuse is blown and the Side
marker, ID & Clearance Lights, Tail Lights, Dome Lights, License Lights
(SFE20) fuse is blown. All other fuses continuity check ok on the ohms
multimeter selection.
Iıd sworn I replaced the instrument 4 amp fuse the first time but Iıve slept
since then. OK maybe itıs only those two fuse positions.
Iıve the Wiring Diagrams for the 1977-1978-Transmode-chassis-electrolevel-I
and 1977-1978-chassis-electrolevel-I. They look pretty much the same.
I have a 1977 Royale which is a Transmode, interior by Craftsman, pretty
well stock.
Having never had a failure of this sort before, finding a direction to go is
a bit random. Normally Iıd look for a likely part common to the failures.
Suggestions appreciated.
John Massey
1977 Royale
Bowie, MD
Steve Southworth wrote on Sat, 26 Jun 2010 02:16:18 -0500
>What year coach do you have. I'm looking at a 73/74 diagram and I see two
fuses associated with the lights. There is a 20A for "tail & dome" and a 4A for
"panel lights". The >4A is actually down stream from the 20A after going
through the panel light dimming resistor. You mention 3 fuses, what is the
third? Actually what is the labeling on the 3 >fuses you blew. Based on what I
can see so far if you are just blowing the 20A dome & tail light and the 4A
panel then the problem does not appear to be in the headlight switch.
>
>--
>Steve Southworth
>1974 Glacier TZE064V100150
>Palmyra WI
J MASSEY wrote on Sat, 26 June 2010 01:02
> Coming home from a rally, I lost lights when it started getting dark.
> Turning on Head Lights blew 3 fuses - dash and exterior lights
> (head lights themselves are ok). I got home just after the sun set.
>
> Repeated the problem several times with new fuses. Looking at the MH?s
> wiring diagram, I suspect a bad headlight switch.
>
>
> Is there a check of the switch I can make that can exclude it as the cause
> of a short in the system without pulling the switch?
>
> Thanks,
>
> JohnM
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| Re: [GMCnet] Electrical Problem, Turning on Head Lights blows 3 fuses - dash and exterior lights (he [message #90227 is a reply to message #90219] |
Sun, 27 June 2010 23:40 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| J MASSEY wrote on Sun, 27 June 2010 22:48 |
Thanks for the response Steve,
Well, I just checked the chassis fuse block and using the terminology from
diagram in my 1977 Transmode Operating Manual (page 64),
The Hazard Warning Light, Stop Light (SFE-20) fuse is blown and the Side
marker, ID & Clearance Lights, Tail Lights, Dome Lights, License Lights
(SFE20) fuse is blown. All other fuses continuity check ok on the ohms
multimeter selection.
snip snip
Having never had a failure of this sort before, finding a direction to go is
a bit random. Normally Iıd look for a likely part common to the failures.
Suggestions appreciated.
John Massey
|
OK - looking at a 77 diagram (thanks bdub) the common areas between the two fuses are the front and rear park/turn/stop lights. The light switch has no area common to both circuits. Likewise the turn/hazard switch has no common areas either. What is common is the wiring harness and the park/tail/turn/stop lamp sockets and bulbs. Now if two wires just shorted together there would be more bulbs lighting up than expected for a specific function but it would be unlikely that a fuse would operate. For the fuses to blow the wiring/circuit needs to be grounded.
I further suspect that, although you are finding two blown fuses, they are not blowing at the same time. What I would do next is to replace the fuses, step on the brakes, run the turn signals and then check the stop/hazard fuse. I suspect it will be blown. Either way, then turn on the lights and check the tail fuse.
So test sequence would be:
replace fuses
activate brakes and/or turn signals
check fuses
replace any blown fuses
turn on lights
check fuses
Then figure out where to go next.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] Electrical Problem, Turning on Head Lights blows 3 fuses - dash and exterior lights (he [message #90230 is a reply to message #90227] |
Mon, 28 June 2010 02:06 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| midlf wrote on Sun, 27 June 2010 23:40 |
| J MASSEY wrote on Sun, 27 June 2010 22:48 |
Thanks for the response Steve,
Well, I just checked the chassis fuse block and using the terminology from
diagram in my 1977 Transmode Operating Manual (page 64),
The Hazard Warning Light, Stop Light (SFE-20) fuse is blown and the Side
marker, ID & Clearance Lights, Tail Lights, Dome Lights, License Lights
(SFE20) fuse is blown. All other fuses continuity check ok on the ohms
multimeter selection.
snip snip
Having never had a failure of this sort before, finding a direction to go is
a bit random. Normally Iıd look for a likely part common to the failures.
Suggestions appreciated.
John Massey
|
OK - looking at a 77 diagram (thanks bdub) the common areas between the two fuses are the front and rear park/turn/stop lights. The light switch has no area common to both circuits. Likewise the turn/hazard switch has no common areas either. What is common is the wiring harness and the park/tail/turn/stop lamp sockets and bulbs. Now if two wires just shorted together there would be more bulbs lighting up than expected for a specific function but it would be unlikely that a fuse would operate. For the fuses to blow the wiring/circuit needs to be grounded.
I further suspect that, although you are finding two blown fuses, they are not blowing at the same time. What I would do next is to replace the fuses, step on the brakes, run the turn signals and then check the stop/hazard fuse. I suspect it will be blown. Either way, then turn on the lights and check the tail fuse.
So test sequence would be:
replace fuses
activate brakes and/or turn signals
check fuses
replace any blown fuses
turn on lights
check fuses
Then figure out where to go next.
|
Why don't you remove the 4 bulbs, inspect and clean the sockets, replace the fuses with the bulbs still removed, and see if either fuse blows. Then proceed from there. I still think you will find one socket corroded and shorted. It will not take you more than 15 minutes to check and clean them.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Electrical Problem, Turning on Head Lights blows 3 fuses - dash and exterior lights (he [message #90243 is a reply to message #90230] |
Mon, 28 June 2010 07:08 |
Jim Bounds
Messages: 842
Registered: January 2004
Karma: 0
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Senior Member |
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Pull the back off the instrument cluster, find the main harness just under the back of your dash radio and see if there is any heat damage there. Cut open the black wrap around the wires and seperate them out to check for this heat damage. I have seen "ghosts in the machine" caused by a partial meltdown of this harness due to the nichrome "toaster' wire there. Good luck, hope this helps,
Jim Bounds
----------------------------
----- Original Message ----
From: Ken Burton <n9cv@comcast.net>
To: gmclist@temp.gmcnet.org
Sent: Mon, June 28, 2010 3:06:41 AM
Subject: Re: [GMCnet] Electrical Problem, Turning on Head Lights blows 3 fuses - dash and exterior lights (he
midlf wrote on Sun, 27 June 2010 23:40
> J MASSEY wrote on Sun, 27 June 2010 22:48
> > Thanks for the response Steve,
> >
> > Well, I just checked the chassis fuse block and using the terminology from
> > diagram in my 1977 Transmode Operating Manual (page 64),
> > The Hazard Warning Light, Stop Light (SFE-20) fuse is blown and the Side
> > marker, ID & Clearance Lights, Tail Lights, Dome Lights, License Lights
> > (SFE20) fuse is blown. All other fuses continuity check ok on the ohms
> > multimeter selection.
> >
> > snip snip
> >
> > Having never had a failure of this sort before, finding a direction to go is
> > a bit random. Normally Iıd look for a likely part common to the failures.
> > Suggestions appreciated.
> >
> > John Massey
>
>
> OK - looking at a 77 diagram (thanks bdub) the common areas between the two fuses are the front and rear park/turn/stop lights. The light switch has no area common to both circuits. Likewise the turn/hazard switch has no common areas either. What is common is the wiring harness and the park/tail/turn/stop lamp sockets and bulbs. Now if two wires just shorted together there would be more bulbs lighting up than expected for a specific function but it would be unlikely that a fuse would operate. For the fuses to blow the wiring/circuit needs to be grounded.
>
> I further suspect that, although you are finding two blown fuses, they are not blowing at the same time. What I would do next is to replace the fuses, step on the brakes, run the turn signals and then check the stop/hazard fuse. I suspect it will be blown. Either way, then turn on the lights and check the tail fuse.
>
> So test sequence would be:
> replace fuses
> activate brakes and/or turn signals
> check fuses
> replace any blown fuses
> turn on lights
> check fuses
>
> Then figure out where to go next.
Why don't you remove the 4 bulbs, inspect and clean the sockets, replace the fuses with the bulbs still removed, and see if either fuse blows. Then proceed from there. I still think you will find one socket corroded and shorted. It will not take you more than 15 minutes to check and clean them.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Electrical Problem, Turning on Head Lights blows 3 fuses - dash and exterior lights (he [message #90252 is a reply to message #90219] |
Mon, 28 June 2010 07:49 |
Sandra Price
Messages: 709
Registered: May 2006
Karma: 1
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Senior Member |
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John, do you have a trailer plug on your coach? If you do, start from
there.
Bob Price
On Sun, Jun 27, 2010 at 10:48 PM, J MASSEY <johnmmassey@verizon.net> wrote:
>
> Thanks for the response Steve,
>
> Well, I just checked the chassis fuse block and using the terminology from
> diagram in my 1977 Transmode Operating Manual (page 64),
> The Hazard Warning Light, Stop Light (SFE-20) fuse is blown and the Side
> marker, ID & Clearance Lights, Tail Lights, Dome Lights, License Lights
> (SFE20) fuse is blown. All other fuses continuity check ok on the ohms
> multimeter selection.
>
> Iıd sworn I replaced the instrument 4 amp fuse the first time but Iıve
> slept
> since then. OK maybe itıs only those two fuse positions.
>
> Iıve the Wiring Diagrams for the 1977-1978-Transmode-chassis-electrolevel-I
> and 1977-1978-chassis-electrolevel-I. They look pretty much the same.
>
> I have a 1977 Royale which is a Transmode, interior by Craftsman, pretty
> well stock.
>
> Having never had a failure of this sort before, finding a direction to go
> is
> a bit random. Normally Iıd look for a likely part common to the failures.
> Suggestions appreciated.
>
> John Massey
> 1977 Royale
> Bowie, MD
>
>
>
>
>
>
>
>
>
>
> Steve Southworth wrote on Sat, 26 Jun 2010 02:16:18 -0500
> >What year coach do you have. I'm looking at a 73/74 diagram and I see two
> fuses associated with the lights. There is a 20A for "tail & dome" and a
> 4A for
> "panel lights". The >4A is actually down stream from the 20A after going
> through the panel light dimming resistor. You mention 3 fuses, what is the
> third? Actually what is the labeling on the 3 >fuses you blew. Based on
> what I
> can see so far if you are just blowing the 20A dome & tail light and the 4A
> panel then the problem does not appear to be in the headlight switch.
> >
> >--
> >Steve Southworth
> >1974 Glacier TZE064V100150
> >Palmyra WI
>
>
>
> J MASSEY wrote on Sat, 26 June 2010 01:02
> > Coming home from a rally, I lost lights when it started getting dark.
> > Turning on Head Lights blew 3 fuses - dash and exterior lights
> > (head lights themselves are ok). I got home just after the sun set.
> >
> > Repeated the problem several times with new fuses. Looking at the MH?s
> > wiring diagram, I suspect a bad headlight switch.
> >
> >
> > Is there a check of the switch I can make that can exclude it as the
> cause
> > of a short in the system without pulling the switch?
> >
> > Thanks,
> >
> > JohnM
>
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
IN GOD WE TRUST!
Sandra and Bob in the 51st Year of our State of Marriage
Lifes a Trip in The Roadhouse
73 Painted Desert
Huntsville, TX
Finally, all of you, live in harmony with one another, be sympathetic, love
as brothers, be compassionate and humble. Do not repay evil with evil or
insult with insult, but with blessing, because to this you were called so
that you may inherit a blessing. --1 Peter 3:8-9
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| Re: [GMCnet] Electrical Problem, Turning on Head Lights blows 3 fuses - dash and exterior lights (he [message #90288 is a reply to message #90252] |
Mon, 28 June 2010 12:26 |
 |
Bob M
Messages: 100
Registered: August 2005
Location: Carlisle, PA
Karma: 0
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Senior Member |
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I recently had a high beam/low beam problem that resulted in no highbeams and the smell of burning insulation. Turned out that the mechanic who replaced my chassis battery had knocked the wire loose from the high beam connection on the headlight. When he replaced it he put it in the slot where the low beam wire was already connected!! Duh. Hopefully, your problem is just something simple like mine was.
Bob Moss
77 Eleganza II
Bob Moss
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