Anybody clued up with electrics? Having just fitted new led light clusters to our box trailer we’ve ran into some problems, firstly when coupled up to a MAN everything works fine until the side lights go on then the indicators flash rapidly. But when anything else is coupled up this doesn’t happen. The only problem is that the indicator flasher on the dash doesn’t work :-/ anyone else had this problem or know a solution? It’s driving me mad, I have stripped it down 3 times to check and check again everything is wired up in the right place! Cheers in advance.
you need to put resistors on the live feeds ot the LEDs, OR try to obtain a fixed flash rate flasher relay.
The rapid firing of the indicators is due to the relay thinking there is a bulb gone in the system, as it isnt pulling enough amps!
the resistors will force more juice through, thus fooling the flasher unit into thinking the bulbs are present!
the fixed flash rate relay solves all of these problems as they do what they say on the tin… flash at a fixed rate regardless of what they’re connected too, thus curing the need for resistors too 
ebay.co.uk/itm/2-x-24V-Balla … 564e5697ea
one of them on the live feed to EVERY LED flasher bulb and you’re away
If its a trailer and likely to be used on other vehicles, i suggest the resistors, as opposed the flasher unit! this will avoid problems if you stick another truck infront of it
HTH
B…
Thanks a lot mate! I’ll give it a whirl. Probably go with the resistors on the live feeds because we have a mixed fleet. It was baffling me because when the side lights were off the indicators would work as they should but when the side lights were turned on and the indicator wasn’t activated the both indicators would flash like crazy. Thanks for the quick reply matey.
dukeofdirt:
Thanks a lot mate! I’ll give it a whirl. Probably go with the resistors on the live feeds because we have a mixed fleet. It was baffling me because when the side lights were off the indicators would work as they should but when the side lights were turned on and the indicator wasn’t activated the both indicators would flash like crazy. Thanks for the quick reply matey.
No probs, let me know how you get on!
if the problem persists a vid and wiring diagram might help
Cheers
B…
Bungle666:
one of them on the live feed to EVERY LED flasher bulb and you’re away
You only need one on each side of the truck, not one per indicator LED. Just connect one between the left indicator circuit and earth and another between the right indicator circuit and earth and it should all start working properly.
Paul
repton:
Bungle666:
one of them on the live feed to EVERY LED flasher bulb and you’re awayYou only need one on each side of the truck, not one per indicator LED.
Paul
Correct.
Also, save paying £11 for a pair and get two Arcol 22R 50W resistors from RS for £1.74 each - its the same thing. They pull 26Watts @ 24V - so should deal with voltage drop down the trailer as well. You’re paying 6 odd quid just for someone to solder some wires to them on ebay…
Not only about current draw also down to test pulse every fifth of a second to check bulb integrity,The system sends a signal to check circuit resistance and LEDs register an infinite resistance below 5 volts (pulse voltage) so it senses a failed bulb.
semtex65:
repton:
Bungle666:
one of them on the live feed to EVERY LED flasher bulb and you’re awayYou only need one on each side of the truck, not one per indicator LED.
PaulCorrect.
Also, save paying £11 for a pair and get two Arcol 22R 50W resistors from RS for £1.74 each - its the same thing. They pull 26Watts @ 24V - so should deal with voltage drop down the trailer as well. You’re paying 6 odd quid just for someone to solder some wires to them on ebay…
So I need to buy 2 of these and connect them to the live feed on both sides of the trailer? Do I need one for each live feed wire, side light, indicator. Etc.
I’m still struggling with one aspect of your original post.
I can understand the indicators flashing erratically if the load is significantly lower than the flasher unit is expecting, and I think everyone is exactly on the money with adding a resister to the left and right flasher circuit on the trailer as described above.
What I can’t instantly reconcile is why the side lights being on or off would make the blindest bit of difference, the only link really being the earth return. Surely the tiny extra bit of current from sticking on the LED side lights wouldn’t cause the indicator current to drop significantly enough to change the behaviour of the flasher relay?! Suppose it’s possible…
If you are going the resistor route I suggest you start with resistors on the left and right flasher circuits on the trailer and see what does.
Personally I would be fixing the problem the fuse box end in the cab, as you can get 3 and 4 pin fixed rate flasher relays that work with LEDs and filament bulbs. They are about £12 on ebay I think. I don’t know whether MANs have a bespoke (expensive) unit like older Scanias did or whether they use ordinary units. If they do it is simple wiring - 3 pin just has negative, positive and load (goes to flasher switch), 4 pin has an extra terminal for the dashboard lamp.
Best of luck
th2013:
I’m still struggling with one aspect of your original post.
I can understand the indicators flashing erratically if the load is significantly lower than the flasher unit is expecting, and I think everyone is exactly on the money with adding a resister to the left and right flasher circuit on the trailer as described above.What I can’t instantly reconcile is why the side lights being on or off would make the blindest bit of difference, the only link really being the earth return. Surely the tiny extra bit of current from sticking on the LED side lights wouldn’t cause the indicator current to drop significantly enough to change the behaviour of the flasher relay?! Suppose it’s possible…
If you are going the resistor route I suggest you start with resistors on the left and right flasher circuits on the trailer and see what does.
Personally I would be fixing the problem the fuse box end in the cab, as you can get 3 and 4 pin fixed rate flasher relays that work with LEDs and filament bulbs. They are about £12 on ebay I think. I don’t know whether MANs have a bespoke (expensive) unit like older Scanias did or whether they use ordinary units. If they do it is simple wiring - 3 pin just has negative, positive and load (goes to flasher switch), 4 pin has an extra terminal for the dashboard lamp.
Best of luck
Thanks mate, I’ll try and get a vid up during the week if I get time. It is weird because when the lights are off then the indicators work fine but when turned on both the indicators flash, not like they would flash when a bulb is out but they both flash as fast as they can constantly even when the indicator/4 ways aren’t on.
dukeofdirt:
So I need to buy 2 of these and connect them to the live feed on both sides of the trailer? Do I need one for each live feed wire, side light, indicator. Etc.
In most cases you will only need two of these resistors (i.e. one pair).
You connect one between the left hand indicator live feed and ground. You connect the other between the right hand indicator live feed and ground. This has the effect of drawing more current through the indicator circuit so that the tractor unit thinks there is a normal filament bulb connected as the LEDs draw so little current the tractor unit thinks that the bulb has failed.
It doesn’t matter where physically on the trailer you fit them, but most people will fit them somewhere near the rear lights as that is where the cables are most accessible.
Doing that should make your indicators work fine.
The only cases you might need more resistors is if your truck has very sensitive bulb failure device and thinks one of the other circuits (i.e. brake or tail/marker lights) has a bulb failure due to it drawing too little current. If that is the case then you will need resistors on those circuits too. For the brake lights you can use the same type as for the indicators (as they are the same bulb rating for filament bulbs - 24V/21W) but for the tail/marker circuit you would need something of higher resistance as you’re only trying to simulate a 24V/5W bulb.
HTH,
Paul
I should probably add that, as per another post above, the behaviour you’re describing does seem rather odd. Electrics is an odd thing though, and sometimes seeming completely unconnected things affect each other, so I would do the resistors on the indicators thing first anyway, as it is something you should always do when replacing trailer lights with LEDs to ensure compatibility with all tractor units.
Then see what problems, if any, you’re left with and report back.
Paul
dukeofdirt:
semtex65:
repton:
Bungle666:
one of them on the live feed to EVERY LED flasher bulb and you’re awayYou only need one on each side of the truck, not one per indicator LED.
PaulCorrect.
Also, save paying £11 for a pair and get two Arcol 22R 50W resistors from RS for £1.74 each - its the same thing. They pull 26Watts @ 24V - so should deal with voltage drop down the trailer as well. You’re paying 6 odd quid just for someone to solder some wires to them on ebay…
So I need to buy 2 of these and connect them to the live feed on both sides of the trailer? Do I need one for each live feed wire, side light, indicator. Etc.
Correct. one per side of the trailer, per function where required - only required if you’re getting bulb failure warning in cab. For tail I’d suggest using an HS25 33ohm - search on RS and it’ll come up. They’ll pull around 16 watts and will even work with Iveco’s fine (they also detect for overload) which are a ■■■■■■■ to get working with LEDs properly
The reason lighting can affect the indicators is due to how LEDs work.They are polarity sensative unlike ordinary incandescent bulbs and in reality the electron flow is from the negative side of the battery(earth) to the positive side.
All the power for the lights,indicators,stops etc flows down through the earth,then the bulbs,switchg and back to the battery.The earth lead on a susie (white) is always thicker than all the other wires as this wire has to carry all the current.
This explains a "bad earth " on indicators.It is not a bad earth it is a bad return.The electons flow down the “earth” lead but cannot ,due to a bad connection or corrosion make a clean return.
The power then sits on the earth tag and will take the next easiest route back to positive through the brake lights and side light bulbs.
Just had to replace the rear Led’s on one of our trailers as the indicator cluster was beginning to fail…looks like they were in sets of 4 or 5 bulbs in a triangular fashion and only had one line left and this couldn’t be seen when the brake lights were on…£300 later for a complete unit and it’s all good…give me normal bulbs any day…one blows, I put another in! Same as the led markers…takes a week from ordering to arrival, minutes worth of work with a normal bulb…PITA these led’s! Tail lights on my car are similar to a long, curly element from an electric fire…hate to think how much they’ll be to replace…bet it ain’t 2 quid like an ‘old fashioned’ buld!!
I would be also looking at what is happening with pin 2 (black) and pin 6 brown on the susie, which are supposed to be LH side lights and RH side lights respectively. I’m wondering whether 2 and 6 are bridged somewhere giving weird earthing results. I would also try disconnecting one of the side light circuits if practical (either in plug or in lamp / connector block) and seeing how this affects the indicators, and whether both side lights still come on, simply as a test.
Basically disconnect things one at a time and note behaviour!
Thanks for all your help guys, nice to see you can still use this forum for help rather than reading about fannys moaning about how bad every other truck driver is. Bit of an update on the trailer, I didn’t end up doing the work on it myself as it needs to be on the road ASAP so one of the lads took it to an auto electrician for them to sort. They fitted resistors on the indicators which cured all the problems on the MAN. However, yesterday I hooked my premium up to it to do a little local job and I had the same problem as I always had. Everything worked fine apart from the indicator tell tale on the dash wasn’t flashing when indicating (the indicators worked fine). So I popped back to the garage that did the work for them to have a look and after much head scratching they couldn’t work out the problem, they tried wiring the resistors up the opposite way and nothing. Eventually they sorted it by wiring normal indicator bulb to each indicator just after the junction box on the chassis! They think for some reason the resistors weren’t compatible with the renault! I’m glad it’s ended up their problem to be honest thanks again for the advice, I’ll post up the solution when it’s sorted for future reference if anybody has the same problem.