RichD1 Posted March 19, 2015 Share Posted March 19, 2015 Just failed my MoT because the rear licence plate lamps have stopped working. After taking the units apart, discovered there was no voltage on the live terminals so started working backwards via the use of the Bentley wiring diagram. Got back to fuse 7 which controls the power to the rear lights and the fuse was OK but there was only about 50mV showing on the multimeter. Next step backward was the lighting switch. How easy is this to get out and where is the connector which lies between this switch and the fuse 7? Can anyone help on this please? Link to comment Share on other sites More sharing options...
proporsche Posted March 19, 2015 Share Posted March 19, 2015 Hi Rich the wire from fuse goes strait to the licence plate light assembly.Did you check the ground? Also the fuse number 7 you have checked is the second from the front of the car ,correct?And you have no power to it? Ivan Link to comment Share on other sites More sharing options...
RichD1 Posted March 19, 2015 Author Share Posted March 19, 2015 Hi Ivan, I only measured about 50mV at fuse 7 so I'm suspecting the light switch. Would like to find the connector which is shown on Bentley diagram between the switch and fuse 7. Link to comment Share on other sites More sharing options...
RichD1 Posted March 19, 2015 Author Share Posted March 19, 2015 Crikey!! Just checked Design911 and a new switch is £135, ouch!! Definitely would like to get the original switch off and see if a dose of contact cleaner will cure. So how easy is the switch to get off? Link to comment Share on other sites More sharing options...
proporsche Posted March 19, 2015 Share Posted March 19, 2015 HI, It is not to hard to take the switch of but i would suggest to disconnect the battery.By removing the switch it is easy to touch the body and make short with the plus wires on the switch. Again did you check the ground on the license light?? Also you can use little jumper wire and cross fuse 6 and 7 with the headlight switch on and see if the lights in the back will come on.The best is with two persons to do this.This way you will know if there is a problem between the 7 fuse and back lights. Ivan Link to comment Share on other sites More sharing options...
RichD1 Posted March 19, 2015 Author Share Posted March 19, 2015 Hi Ivan, the rear lamp holders were in quite a bad state, so I've got some new ones to fit. Haven't checked the earth yet but as there wasn't any power on the feed wire I decided to purse this possibility first. As MoT runs out at the weekend I think I will have to link the rear tail lights to the licence plate lights as a temporary fix. Can the headlight switch on the dash be taken apart or is it sealed? Do you think a dosing in contact cleaner will help? Link to comment Share on other sites More sharing options...
R2D2 Posted March 19, 2015 Share Posted March 19, 2015 Rich - could be the switch but more likely to be the ground and Ivan says. The switch can be taken apart but its a bit of a Pandora's box so if you do go this route take lots of pics and mark the orientation of the parts as they come apart. Link to comment Share on other sites More sharing options...
proporsche Posted March 19, 2015 Share Posted March 19, 2015 Rich ..yes the ground is important....try as i said connect the 6+7 fuses and see the lights,if they come on.This way you can be sure they come on with the headlight switch.The 6 fuse is left is right head light .So no harm done this way.Or connect it in the back to the tail light assembly,for now. Ivan Link to comment Share on other sites More sharing options...
Nige Posted March 19, 2015 Share Posted March 19, 2015 Just hotwire onto the rear lights for the mot. Link to comment Share on other sites More sharing options...
RichD1 Posted March 19, 2015 Author Share Posted March 19, 2015 Hi Nige, linking to side lights was my thoughts to get thro' MoT. When I get the new number plate light holders I'll be able to check out the earth, but with only seeing around 50mV at fuse 7 from the switch points to this being the problem. Link to comment Share on other sites More sharing options...
proporsche Posted March 19, 2015 Share Posted March 19, 2015 Hi Also check number 5 fuse it is connected to the same circuit.Make sure it has a power at the fuse box Ivan Link to comment Share on other sites More sharing options...
Nige Posted March 19, 2015 Share Posted March 19, 2015 The wiring on these is well crummy especially when it passes through the bumperettes Link to comment Share on other sites More sharing options...
RichD1 Posted March 20, 2015 Author Share Posted March 20, 2015 Hi Guys, all sorted fairly easily in the end. My Indie fitted the new bulb holders & then studied the official Porsche wiring diagram and it is different to the one in Bentley!!! The Porsche diagram for MY86 shows an in-line fuse which takes the power to the rear, eventually found this fuse tucked away under the main fuse board & sure enough the fuse had blown. Put in a replacement and all is now well and a pass for the MoT. This in-line fuse was only fitted for MY86, MY85 & MY87 the power comes for fuse 7. Thanks for all the help and advice, I'm going to have to find a copy of the official Porsche wiring for future reference. Link to comment Share on other sites More sharing options...
proporsche Posted March 20, 2015 Share Posted March 20, 2015 Hi Rich:congrats Ivan Link to comment Share on other sites More sharing options...
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