C5 2.2 Diesel Estate Hi Level Brake Light

[Guest GS2C5]

Hi all. My first post and I need help to change the LED unit. In the handbook it gives no info. at all and it doesnt mention a fuse for the circuit. MOT due 21/8/08 so any advice welcome.

GS2C5

[Guest Allan's-C5]

Hi all. My first post and I need help to change the LED unit. In the handbook it gives no info. at all and it doesnt mention a fuse for the circuit. MOT due 21/8/08 so any advice welcome.

GS2C5

 

Hi GS2C5

 

As far as I know, the high level LED brake lights are fed off the same fuse (F5) as the main left brake light (the RH light is on F12), thus if non of your high level LED’s are working yet your other 21watt lights are, then your high level probably have an open circuit.

 

This happened to me when I first purchase my 2002 car 2nd hand. The high level lights can be accessed by opening the rear hatch window and removing two centre T30 Torx screws and another two T30 outer flat head bolts from the hinge assembly to release the top outer casing which holds the module from behind as I remember.

 

The light fitting itself can be taken apart and consists of a simple pcb with four clusters of 4 parallel LED’s connected in series with the other clusters (16 in all). The most likely cause of the open circuit (if 12v appears at the connector when brake pedal activated) is ingress of rain water rotting the resistors connected in series with these LED’s to drop the nominal 12v down to 6-8v. It’s probably these resistors which need to be replaced and the fitting re-sealed.

 

A replacement module may cost you £60-70. An alternative is to replace the series resistor (150ohm 0.5watt) for about 10p, a bit of soldering and half a day of your own labour?

 

Best of Luck

Allan

[PICASSOCONVERT]

Allan's C5, thank you for your helpful post on this topic. I removed the high level brake light from my son's 51 reg estate easily following your instructions yesterday and confirmed that 12 volts was reaching the connector.

 

However, I just cannot see how to dis-assemble the light unit, to check/replace the resistors as you suggest, as it appears to be a sealed unit.

 

Any guidance on this would be much appreciated.

 

Also, as I have returned home and so do not have the car to hand, do you know if the light unit is damaged if the polarity is reversed, as I didn't have my voltmeter with me to check which leads were +ve and -ve yesterday.

 

Thanks in advance for any help.

[PICASSOCONVERT]

A morning spent fiddling and I can now answer my own questions.

 

First off, the red lens can be separated from the black plastic body by carefully inserting a thin knife blade between the lens and the body. The lens has 8 rectangular holes (4 top and 4 bottom) which locate on 8 lugs on the inside of the black plastic housing. A bit fiddly and probably a risk of cracking the red lens, but can be done.

 

Second, the polarity is marked on the printed circuit board.

 

Thirdly, there appear to be 4 off 5ohm (light greenish in colour) resistors and 1 off 150 ohm resistor (in the centre), but my measurements may be a bit hit and miss as my multimeter only cost £3.99!

 

Sure enough one of the resistors has crumbled away, despite there being no sign of water ingress in the light.

 

Now off to find some new resistors - may as well replace them all while I've got the light in bits.