LEDs in indicators

Submitted: Monday, Jan 29, 2018 at 13:23
ThreadID: 136177 Views:2686 Replies:6 FollowUps:8
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Hi one for the electrical gurus. I fitted LED globes in the indicator lights on my Jayco camper. They work fine as indicators but don't flash with the hazard flashers.
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Reply By: Blown4by - Monday, Jan 29, 2018 at 14:38

Monday, Jan 29, 2018 at 14:38
Depending on the tow vehicle and its flasher unit, sometimes LED lamps fail to illuminate or flash way too fast because the LED lamps draw such a small amount of current hence they offer an insignificant amount of resistance for the flasher unit to recognise them. You have probably seen some semi-trailers where the stop lamps flicker all the time they are illuminated instead of being 'on solid' as is required. Narva and probably others make a number of LED lamp load resistors for this purpose which is fitted to each lamp and provides the resistance required to make the LED lamps operate correctly. The other alternative is an electronic flasher unit which is designed to operate with the lower resistance LED lamps. Narva LED Lamp Load Resistors
AnswerID: 616466

Follow Up By: RMD - Monday, Jan 29, 2018 at 17:27

Monday, Jan 29, 2018 at 17:27
The OP has stated the lamps work properly when used as the indicators, ie Flasher unit not the issue, BUT when supplied with current from the vehicle it's flashers are working but the trailer isn't working properly. The current to supply each trailer lamp is coming through the same wires.
If the vehicle works ok, then anything connected to the vehicle is additional load and if anything, may make the flashers run slower.

Only if you lighten the electrical load does the flasher unit run fast.
Load resistors and the like isn't the problem as far as I can see.

Often with semi trailers the lamps are multi voltage and when fed 24v the LED lights see, first 12v and then 24v and they change in brightness. If the total load of the circuit is a bit much for the connections in the systems, ie, resistance, and the applied voltage to the LEDS keeps changing and that makes them vary

I have some truck LEDS white, orange and red stop/tail. They are buggers of things to make work without the brightness varying as it jumps from 12 to 24 mode. However, the OP hasn't got truck lamps, just replacement globes.
FollowupID: 887835

Follow Up By: tim_c - Friday, Feb 02, 2018 at 10:02

Friday, Feb 02, 2018 at 10:02
I would still look at the tow vehicle - older vehicles simply connected the left and right turn signal circuits together at the hazard light switch - newer cars aren't quite so simple with all of this being chip controlled now. It is probably a different program that runs the hazards compared to the turn signals.

How often do you use hazard flashers anyway? Unless you vehicle is physically unable to be moved, there should rarely any need to use hazard warning lamps (other than when driving thick fog where they are permitted) - if your vehicle is in a position that is causing a hazard, you should move your vehicle to somewhere it won't be a hazard rather than just flicking on your warning lamps.
FollowupID: 887998

Reply By: RMD - Monday, Jan 29, 2018 at 14:39

Monday, Jan 29, 2018 at 14:39
G'Day Bob
Did the original globes actually work while on Hazard running? I would suspect they didn't if the LED globes don't also.

Without further info I would think the negative side of each lamp is connected to the other side positive wire and when one side is operated the lamp earths through that side wiring.
I presume the fault is in the trailer plug and not the base on the vehicle because ( I presume) the vehicle all works normally.

Have you connected a power supply or battery negaive side to pin 3 of the plug and then applied power 12v +ve to pin 1 LHS and Pin 4 RHS to see if ti work correctly?

Just opening the plug may reveal some issue.
AnswerID: 616467

Follow Up By: IvanTheTerrible - Monday, Jan 29, 2018 at 19:47

Monday, Jan 29, 2018 at 19:47
The left and right indicators work separately so I cant see the plug being wrong.
FollowupID: 887849

Follow Up By: RMD - Monday, Jan 29, 2018 at 19:58

Monday, Jan 29, 2018 at 19:58
But they can earth through the other side and appear to operate normally. When both positive supplies to the L&R indicators are fed via the hazards then the earthing via the other side is negated and the lights won’t operate.
FollowupID: 887852

Follow Up By: IvanTheTerrible - Monday, Jan 29, 2018 at 20:08

Monday, Jan 29, 2018 at 20:08
They are LEDS. Light Emitting Diodes. Diodes only conduct one way. You cant conduct backwards
FollowupID: 887855

Follow Up By: RMD - Monday, Jan 29, 2018 at 22:33

Monday, Jan 29, 2018 at 22:33
We are not talking about back flow through a one way diode at all.
Not sure why you think that.
The lights on the trailer CAN find a return path through the wiring of trailer and the vehicle indicator system. There won't be current flowing backwards through the diodes at all. Simply power applied to a LED globe CAN, if it's earthing isn't correct, to find a path through the opposite side of the vehicle system. We don't actually know what is happening there yet. When both sides of the system are powered, ie, hazards are on. the power is applied to both sides and so one side or the other cannot find that path because there is the same polarity at both sides at the same time. It is a fault somewhere. Maybe in the plug.

Some systems rely on that happening to turn a light OFF. ie, ALt charge light on, engine stopped. Start engine, alt charges and same voltage appear across the indicator globe, which indicates it is charging. Some of those are LEDS too.
FollowupID: 887866

Reply By: Bob M73 - Tuesday, Jan 30, 2018 at 08:55

Tuesday, Jan 30, 2018 at 08:55
Thanks guys for all the input though I got lost a bit in some of the technicality. I can't see how there are any wiring issues as the lights work fine both indicating and when hazard flashing with normal globes in. The low resistance idea of the LEDs makes some sense to me though I would have thought that if one LED worked as an indicator then when more lights were being operated as in hazard flashers then the LED would work then too.
AnswerID: 616501

Follow Up By: Bob M73 - Wednesday, Jan 31, 2018 at 12:15

Wednesday, Jan 31, 2018 at 12:15
Ok I've now spent more time on this. At first I only fitted an LED globe to one indicator light. That was when that light didn't flash with the hazard flashers. When I fitted an LED into both indicators they both work as normal. The LEDs flicker slightly when operating but when indicating they are much brighter than normal globes. When the hazard flashers are used the LEDs are not as bright but serviceable and the increased brightness of the indicators make the change worthwhile. Thanks for all the comments.
FollowupID: 887919

Follow Up By: tim_c - Friday, Feb 02, 2018 at 10:10

Friday, Feb 02, 2018 at 10:10
We had the opposite problem - the caravan had two turn-signal lamps for each direction (one at the rear, one on the side near the front). While the Prado had no issue with the standard globes, the X-Trail flasher controller couldn't handle the load and the lamps would just stay on continuously. I replaced the front side turn signal lamps will LEDs to reduce the load and we can now tow the van with either vehicle.
FollowupID: 888002

Reply By: Iza B - Tuesday, Jan 30, 2018 at 10:39

Tuesday, Jan 30, 2018 at 10:39
If you disable either left or right indicator clusters, will the still connected indicator flash when the hazard lights are set?

AnswerID: 616502

Reply By: Member - Lyncol - Tuesday, Jan 30, 2018 at 23:22

Tuesday, Jan 30, 2018 at 23:22
Not knowing the vehicle type makes things tricky but some have two units one for indicators the other hazards, if so unit can be changed to recognise leds . Also has it got a controller at the back eg. BT50, Colorado?
AnswerID: 616523

Reply By: The Bantam - Tuesday, Feb 13, 2018 at 23:30

Tuesday, Feb 13, 2018 at 23:30
It is most likely you have a problem in the common negative ( there are no earth wires in cars).

when running as indicators the return path will be thru the indicator filament lamps in the tow vehicle.
when both sides are powered by the hazard flashers there is no return path thru the indicators in the vehicle because both sides are powered.

BETYA the is a problem in the common negative.

AnswerID: 616906

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