30-6 Posted May 31, 2016 Report Share Posted May 31, 2016 Anyone help with this? On my son's car, the brake light's either side are not working. Bulbs are OK, no corrosion anywhere, but when a meter is put on they are only getting 8.6v, bulbs that are working are getting correct 12v. Quote Link to comment Share on other sites More sharing options...
saddler Posted May 31, 2016 Report Share Posted May 31, 2016 Needs his brake light fluid topping up? Quote Link to comment Share on other sites More sharing options...
la bala Posted May 31, 2016 Report Share Posted May 31, 2016 I know you have low voltage, but have you checked earth . Quote Link to comment Share on other sites More sharing options...
30-6 Posted May 31, 2016 Author Report Share Posted May 31, 2016 Done a continuity test across a bolt on either side of light cluster fittings, offside to nearside, and had a circuit between them. All bulbs on both sides work except 1 reverse and both brake. Battery engine off 12.2, running 14.3 Quote Link to comment Share on other sites More sharing options...
Dano0404 Posted May 31, 2016 Report Share Posted May 31, 2016 More than likely a broken wire some where or the switch by the brake pedal is at fault. Do the wires run through flex where the boot opens? I've had them brake there before. Quote Link to comment Share on other sites More sharing options...
ph5172 Posted May 31, 2016 Report Share Posted May 31, 2016 You have low voltage on the *** side if I recall so assume you checked the bulb connector *** to Earth. Have you checked for voltage on the earth / neg bulb connector back to earth / neg. if there is voltage there it may be a bad earth *** p o s has been blocked by the swear filter!! It should read positive Quote Link to comment Share on other sites More sharing options...
30-6 Posted May 31, 2016 Author Report Share Posted May 31, 2016 Checked bulb holders of affected bulbs, + to earth for voltage showed 8.6v, checked bulb holder earth to chassis bolt with continuity, had circuit. All working bulbs showed 12v. Brake bulbs on both sides bad and 1 reverse. Quote Link to comment Share on other sites More sharing options...
Schmitty Posted June 1, 2016 Report Share Posted June 1, 2016 What type of car is it? Is there any verde gris on the connectors at the light cluster, switch or fuse box? This can drop the voltage. Is there any moisture in the light cluster, switch or fuse box? This can drop the voltage. Run a 12V+ link wire from a known good source (e.g.tail lights or battery) to the brake light cluster. If it works then the earth is fine and its the supply to/from the switch. If it doesn't then its an earth fault in which case disconnect the existing earth and run a temporary one to a known good connection and try again. Quote Link to comment Share on other sites More sharing options...
fortune Posted June 1, 2016 Report Share Posted June 1, 2016 Bad earth and If you are using a digital meter they sometimes give a false reading.get bulb and a piece of wire and go from the live in the bulb socket through the bulb to a good earth. Quote Link to comment Share on other sites More sharing options...
30-6 Posted June 1, 2016 Author Report Share Posted June 1, 2016 I thank you all for your input into this problem, my son just phoned and it is now sorted. The reverse light mentioned was actually the fog light which worked ok, only one reverse and one fog on his car, my error apologies for any confusion. He was told there is a plunger type switch under the fusebox in the passenger footwell which is energised when the brake pedal is depressed and this makes the circuit to the rear brake lights. Apparently they gum up. Took it to an auto electrical garage and they done it in 10 minutes. Once again I thank you for all your help. Quote Link to comment Share on other sites More sharing options...
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