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| L E D lights won't flash [message #160533] |
Thu, 16 February 2012 11:48  |
Wander Inn
Messages: 100
Registered: January 2010
Location: Phoenix Az.
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I just installed L E D lights for my front and back
turn signals, they will four way flash but the turn
signals do not work. What's the fix?
Mike
Mike & Chris Hughes
1977 Kingsley
Phoenix, Az.
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| Re: [GMCnet] L E D lights won't flash [message #160535 is a reply to message #160533] |
Thu, 16 February 2012 11:58  |
Kudzu
Messages: 377
Registered: November 2011
Location: Marshville, NC
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The LEDs may not have enough draw to trip the relay. Put an old bulb in
front or back and see if that does it. There is a module you can add to
overcome this but I don't recall the name.
Dan in NC
Caregiver to a 1976 Eleganza II
"Tzetze Fly"
On 2/16/2012 12:48 PM, Mike & Chris Hughes wrote:
>
> I just installed L E D lights for my front and back
> turn signals, they will four way flash but the turn
> signals do not work. What's the fix?
>
> Mike
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1976 Eleganza II
1996 Chevy Impala SS
1999 Kawasaki Vulcan Nomad
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| Re: [GMCnet] L E D lights won't flash [message #160554 is a reply to message #160533] |
Thu, 16 February 2012 17:12 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
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Pad each side with about a 20 - 25 Ohm 10Watt resistor. The single pair of LEDs aren't drawing enough current to heat the bimetal in the flasher.
--=johnny
'76 23' transmode Norris
'76 Palm Beach
________________________________
From: Mike & Chris Hughes <whose38@yahoo.com>
To: gmclist@temp.gmcnet.org
Sent: Thursday, February 16, 2012 12:48 PM
Subject: [GMCnet] L E D lights won't flash
I just installed L E D lights for my front and back
turn signals, they will four way flash but the turn
signals do not work. What's the fix?
Mike
--
Mike & Chris Hughes
1977 Kingsley
Wander Inn
Phoenix, Az.
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] L E D lights won't flash [message #160595 is a reply to message #160554] |
Thu, 16 February 2012 22:06 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
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| Johnny Bridges wrote on Thu, 16 February 2012 17:12 |
Pad each side with about a 20 - 25 Ohm 10Watt resistor. The single pair of LEDs aren't drawing enough current to heat the bimetal in the flasher.
--=johnny
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Johnny - you will have to explain "pad" as many of the non-electrically familiar will not understand a term that is standard in your business.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: L E D lights won't flash [message #160608 is a reply to message #160533] |
Thu, 16 February 2012 23:15 |
Larry C
Messages: 1168
Registered: July 2004
Location: NE Illinois by the Illino...
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The old incadescent bulb filiment has a resistance of about 50 ohm, plus or minus. The standard flasher uses that resistance to work.
This is why the flasher slows down when you have a bulb burnt out in a multi bulb stop light or stops blinking completely in a single bulb stop light.
A LED light has no where near that resistance so the flasher thinks there is no bulb working.
The Heavy Duty flasher ( generally put in for trailer towing, toads, etc ) has a resister built in and does not rely on the bulb filiment resistance.
Gatsbys' CRUISER  08-18-04
74 GLACIER X, 260/455-APC-4 Bagg'r
Remflex Manifold gaskets
CampGrounds needed, Add yours to "PLACES" />
http://www.gmceast.com/travel
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| Re: [GMCnet] L E D lights won't flash [message #160615 is a reply to message #160608] |
Fri, 17 February 2012 00:55 |
rssbob
Messages: 259
Registered: January 2004
Location: La Mesa, Ca. (San Diego a...
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No offense intended, however the note below is partially correct.
Let's talk about current flow.
When you apply 12 vdc to a standard bulb with a filament that has 50 ohms resistance it establishes a current flow of 240 milliamps. In our turn signal circuits there are several 12v bulbs in parallel, which increases the current flow by that amount for each additional bulb. The more bulbs you add, the faster the flasher will operate. Example 4 bulbs would draw 960 milliamps, almost one amp.
LEDs have very little resistance and if used by themselves would burn out as soon as the voltage is applied. So, we install a resister in series with each LED to limit the current to (as an example) 20 milliamps, much less than the standard bulb so the flasher unit filament will not get hot enough to cause the internal circuit to make contact. The LED running lights are a complete assembly that already has the current limiting resistor installed.
When you say that you can add a resistor to the circuit to make it work, it must be the correct value and it must be installed in PARALLEL with the led assembly. In order to know the correct resistor value you need to know the forward voltage drop of the LED, and know what current flow you want and then calculate from there.
I saw a post or two that said there are flashers on the market that were made for LED lights so I suppose that would be the easier way to go.
On Feb 16, 2012, at 9:15 PM, Larry C wrote:
>
>
> The old incadescent bulb filiment has a resistance of about 50 ohm, plus or minus. The standard flasher uses that resistance to work.
> This is why the flasher slows down when you have a bulb burnt out in a multi bulb stop light or stops blinking completely in a single bulb stop light.
>
> A LED light has no where near that resistance so the flasher thinks there is no bulb working.
>
> The Heavy Duty flasher ( generally put in for trailer towing, toads, etc ) has a resister built in and does not rely on the bulb filiment resistance.
> --
> Gatsbys' CRUISER :d 08-18-04
> 74 GLACIER X, 260/455-APC-4 Bagg'r
> Remflex Manifold gaskets
>
> CampGrounds needed, Add yours to "PLACES" />
> http://www.gmceast.com/travel
>
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Bob Sobrito
78 Palm Beach
La Mesa, Ca
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| Adjustable flasher [message #160620 is a reply to message #160544] |
Fri, 17 February 2012 06:26 |
bukzin
Messages: 840
Registered: April 2004
Location: North California
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Have any of you tried one of the adjustable flashers?
Can someone share a part number? Or supplier?
Bukzin
1977 Palm Beach
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| Re: [GMCnet] L E D lights won't flash [message #160623 is a reply to message #160595] |
Fri, 17 February 2012 06:33 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
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Oops. Parallel the resistor with the lamp. This is the cheap out if you happen to have a stock of resistors kicking around. The proper out is to change the flasher to a newer solid state one.
--johnny
'76 23' transmode norris
'76 palm beach
From: Steve Southworth <midlf@centurytel.net>
To: gmclist@temp.gmcnet.org
Sent: Thursday, February 16, 2012 11:06 PM
Subject: Re: [GMCnet] L E D lights won't flash
Johnny Bridges wrote on Thu, 16 February 2012 17:12
> Pad each side with about a 20 - 25 Ohm 10Watt resistor. The single pair of LEDs aren't drawing enough current to heat the bimetal in the flasher.
>
> --=johnny
>
Johnny - you will have to explain "pad" as many of the non-electrically familiar will not understand a term that is standard in your business.
--
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] L E D lights won't flash [message #160634 is a reply to message #160615] |
Fri, 17 February 2012 07:03 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Well, if we're gonna be totally correct, we also have to point out, the resistance of the light bulb (not the LED) changes drastically from cold to hot. When unlit, it is very nearly a direct short - the resistance is quite low. Illuminated, it's substantially higher. Take your trusty meter and measure the resistance cold. Then set it for current, and light the bulb. Use Ohm's Law to calculate the hot resistance (12/current in amps) If the bulb draws 250MA, it would have a resistance hot of just under 50 Ohms.. Measured cold, the same bulb will measure around 1 Ohm or less. A characteristic the lighting designer has to take into consideration, and one which is quite useful in other applications.
--johnny
'76 23' trandmode Norris
'76 palm beach
From: robert sobrito <rssbob@cox.net>
To: gmclist@temp.gmcnet.org
Sent: Friday, February 17, 2012 1:55 AM
Subject: Re: [GMCnet] L E D lights won't flash
No offense intended, however the note below is partially correct.
Let's talk about current flow.
When you apply 12 vdc to a standard bulb with a filament that has 50 ohms resistance it establishes a current flow of 240 milliamps. In our turn signal circuits there are several 12v bulbs in parallel, which increases the current flow by that amount for each additional bulb. The more bulbs you add, the faster the flasher will operate. Example 4 bulbs would draw 960 milliamps, almost one amp.
LEDs have very little resistance and if used by themselves would burn out as soon as the voltage is applied. So, we install a resister in series with each LED to limit the current to (as an example) 20 milliamps, much less than the standard bulb so the flasher unit filament will not get hot enough to cause the internal circuit to make contact. The LED running lights are a complete assembly that already has the current limiting resistor installed.
When you say that you can add a resistor to the circuit to make it work, it must be the correct value and it must be installed in PARALLEL with the led assembly. In order to know the correct resistor value you need to know the forward voltage drop of the LED, and know what current flow you want and then calculate from there.
I saw a post or two that said there are flashers on the market that were made for LED lights so I suppose that would be the easier way to go.
On Feb 16, 2012, at 9:15 PM, Larry C wrote:
>
>
> The old incadescent bulb filiment has a resistance of about 50 ohm, plus or minus. The standard flasher uses that resistance to work.
> This is why the flasher slows down when you have a bulb burnt out in a multi bulb stop light or stops blinking completely in a single bulb stop light.
>
> A LED light has no where near that resistance so the flasher thinks there is no bulb working.
>
> The Heavy Duty flasher ( generally put in for trailer towing, toads, etc ) has a resister built in and does not rely on the bulb filiment resistance.
> --
> Gatsbys' CRUISER :d 08-18-04
> 74 GLACIER X, 260/455-APC-4 Bagg'r
> Remflex Manifold gaskets
>
> CampGrounds needed, Add yours to "PLACES" />
> http://www.gmceast.com/travel
>
> _
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] L E D lights won't flash [message #160638 is a reply to message #160623] |
Fri, 17 February 2012 07:45 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| Johnny Bridges wrote on Fri, 17 February 2012 06:33 |
Oops. Parallel the resistor with the lamp. This is the cheap out if you happen to have a stock of resistors kicking around. The proper out is to change the flasher to a newer solid state one.
--johnny
'76 23' transmode norris
'76 palm beach
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I think you are making ore of this than necessary. As Johnny says Go to AZ and get a variable load flasher.
Some modern vehicles use the Body Control Module as the flasher. They have no separate flasher. In those cases you need to add a parallel resistor (I have not calculated the value) to make them work correctly. This system is NOT on our GMCs.
Install a new (correct) flasher.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] L E D lights won't flash [message #160646 is a reply to message #160608] |
Fri, 17 February 2012 09:09 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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This is a good article from Superbright LED's, on how to install LED's and answers may other question that many may have.
<http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fcarbulb-notes.htm>
http://tinyurl.com/ybcf6e7
J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 Buskirk 30' Stretch
1975 Avion (Under Reconstruction)
Michigan
On the road in Tucson
On Feb 16, 2012, at 10:15 PM, Larry C wrote:
>
>
> The old incandescent bulb filament has a resistance of about 50 ohm, plus or minus. The standard flasher uses that resistance to work.
> This is why the flasher slows down when you have a bulb burnt out in a multi bulb stop light or stops blinking completely in a single bulb stop light.
>
> A LED light has no where near that resistance so the flasher thinks there is no bulb working.
>
> The Heavy Duty flasher ( generally put in for trailer towing, toads, etc ) has a resister built in and does not rely on the bulb filament resistance.
> --
> Gatsbys' CRUISER :d 08-18-04
> 74 GLACIER X, 260/455-APC-4 Bagg'r
> Remflex Manifold gaskets
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] L E D lights won't flash [message #160649 is a reply to message #160646] |
Fri, 17 February 2012 09:24 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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Also, keep in mind that there are two different flasher schemes in the GMC. Early coaches used a single flasher for both turn signals and 4 ways. Those flashers aren't sensitive to the resistance and hence the number of bulbs. NHTSA passed rule making that required an indication for the driver if a turn signal bulb was inactive. That's when the GMC went to a separate flasher for the turn signals that would flash noticeably faster if a bulb was out. The flasher for the 4 ways was then separate and not sensitive to resistance.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: L E D lights won't flash [message #160663 is a reply to message #160533] |
Fri, 17 February 2012 10:45 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Here is the part that you need to solve your problem.
GROTE 44891
http://www.vehiclesafetysupply.com/product/GRT-44891.html
Or
http://m.summitracing.com/parts/GTE-44891
There is an extra wire coming from the flasher that you have to extend and screw to a good ground.
Stop reading here if you don't care why. 
For those that do:
The simple reason for the problem is that the LED light assembly actually has Too much resistance, (due to the current limiting resistors) stopping the factory circuit from working properly. The flasher uses the low resistance of the regular bulbs as a ground. (resistors in parallel reduce total resistance)
if the original flasher is a factory bimetal strip style, that is specifically designed for the vehicle, this is what happens: if one Bulb burns out the flasher has more resistance and then slows down or stops, indicating to the driver there is a problem.
If you add more bulbs by adding a trailer, there is is even less resistance and the flasher speeds up. (some of you experienced this and then changed to a HD flasher.)
When changing to LEDs Some people have used resistors (to ground) in the directional circuit to act the same as regular bulbs, fooling the flasher to work. (by providing the proper ground) These resistors get just as hot as a bulb (and use as much battery) therefore not really a good option.
By providing the ground to the new electronic flasher, the flashing circuit does not care what happens to the light bulb, it simply provides a pulsating voltage at a frequency of 75 to 100 ons and offs per minute .
I give you the part number because:
You know how it is when you get to the part store: (nobody knows anything) the only thing the person knows is how to answer the questions on the computer. (starting with what is the year and make of your vehicle). This of course stops any productive help because the GMC is nowhere to be found in the computer.
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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