Ask The Experts!

Indicator repeaters

Total Posts: 1
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Posted: 4 years ago
Apparently some cars don't need a trailer repeater for their indicators if manufactured since 2005 and they have an integral checking system for the car (and trailer) lights. Has anyone else come across this?
Total Posts: 228
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Posted: 4 years ago
Yup my car is a volvo xc 70 and if any of the lights are out on the caravan it shows on the dash
Total Posts: 270
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Posted: 4 years ago
Eye eye, my 2008 Rav4 doesn't have a repeater, saves having yor eardrums pierced and doing your head in with the noise when indicating, only trouble is I haven't managed to work out exactly how it will tell me if there's a problem...
Total Posts: 314
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Posted: 4 years ago
my 2002 Freelander has a built in 'trailer light' on dash that tells you all is well (or not)!!
Total Posts: 169
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Posted: 4 years ago
i thought it was the law to have an audible alarm when indicators were used
Total Posts: 45
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Posted: 4 years ago
When I had the towing electrics fitted to my '09 Passat, I wasn't even aware of the change in regs since I last towed. The repeater which came with the kit was fitted in the boot and is just audible enough to be effective and not intrusive.
I'm not aware of any in car repeater warnings as mentioned on Volvo and Land Rover.
Total Posts: 122
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Posted: 4 years ago
MY 62 Yeti Elegance has a green warning light and clicker when a bulb blows like when a flasher is working. I was informed by main dealership it would do same when towing van which did away with extra relay but fridge would still work my electrics are 13 pin. My wife on one trip kept informing me I was still indicating which I said I wasn,t so I pulled in to service station and checked book and found out a brake light had blown after doing test,it does same if you leave hand brake on if only one notch from off.I believe it is to do with the resistance (ohms) if the filiment in a bulb brakes the resistance drops which brings in the alarms but how does it work when you have more bulbs in circuit those on your van they must over come the lost resistance of the one bulb which has blown in car or van. I can only think that the extra resistance created on the cars relay tells the engine management box that the resistance has IE doubled and adjusts to suit. has anybody have other thoughts on this or knows exactly how it works
Total Posts: 22
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Posted: 4 years ago
Modern car electrics are controlled by the ECU. When you plug your trailer or caravan lead into the car, then turn on the ignition, the ECU senses the trailer/caravan is connected digitally by sensing the extra load on the wiring. Next, the ECU sends a digital pulse down each wire for each part of the lighting system. Example, a digital pulse is sent down the left direction indicator line. If the buld filament is not broken, the signal will continue through the filament and back through the ground return. This is sensed and marked good. The system is repeated for each line. Obviously, if the filament was faulty, the signal would not return, so a faulty bulb

Now, as the ground return is normally a single common wire, sending the same pulse down each lamp wire wouldn't be any good, so a different digitally coded pulse is used for each lighting wire. This way, the ECU knows which bulb, if any, is faulty, so can tell you which it is.

So, what is the easiest way to check that the car sensors are working correctly? Simply remove each caravan bulb in turn, but just one at a time, turn the ignition on each time, and you should get the relevant faulty bulb warning on your dash.
Hope that helps.
Total Posts: 22
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Posted: 4 years ago
Oops, I missed a bit. See above:- **Obviously, if the filament was faulty, the signal would not return, so a faulty bulb** error will be flagged and shown on the dashboard display.