derek500 Posted October 21, 2009 Share Posted October 21, 2009 As thread title. 1. It's not the bulb. 2. With ignition on and in reverse, my multimeter shows just under 12v on the contacts. 3. With ignition on and not in reverse it shows zero. 4. With ignition on and in reverse with bulb in, multimeter shows zero. Any bright sparks out there, with any ideas? Link to comment Share on other sites More sharing options...
Brambles Posted October 21, 2009 Share Posted October 21, 2009 OK, another test for you, do all the other lights work properly? 2. measure the contavt voltages again with respect to teh chassis ground, with the bulb in an dreverse selcted. Is it 12 volts on both contacts or 0 volts? This will etsablish if fault is in gnd connection or 12 volt feed connection. If in ground, then check ground connection is sound and clean. If supply, then you will need to check for 12 volts at the gearbox switch to see if before or after switch where the fault occurs. Hope this helps progress the trouble shooting a bit. Jon. Link to comment Share on other sites More sharing options...
dikyenfo Posted October 21, 2009 Share Posted October 21, 2009 V common fault with vans. Just fitted new one myself and are cheap to buy. You need to use a screwdriver to eject the wire lock from the plug-in bit with the wires on before you unscrew the switch body. Link to comment Share on other sites More sharing options...
Guest Tracker Posted October 21, 2009 Share Posted October 21, 2009 Dirty contacts or locating pin missing from bulb are two more possibilities? Link to comment Share on other sites More sharing options...
Brambles Posted October 21, 2009 Share Posted October 21, 2009 Tracker, agree that could stop the bulb lighting but does not explain the zero volts across the contacts, so either the 12 volts supply has high resistance or the Gnd connection has high resistance. Jon. Link to comment Share on other sites More sharing options...
derek500 Posted October 22, 2009 Author Share Posted October 22, 2009 measure the contact voltages again with respect to the chassis ground, with the bulb in and reverse selected. Is it 12 volts on both contacts or 0 volts? This will etsablish if fault is in gnd connection or 12 volt feed connection. Thanks. How do I do the above? Do I just put the negative probe somewhere on the chassis? As all the bulbs in the cluster share the same ground strip, would that mean the ground is OK as the others are working? Link to comment Share on other sites More sharing options...
Brambles Posted October 22, 2009 Share Posted October 22, 2009 As the other bulbs are all working it would mean the gnd is probably OK, Yes, use the chassis for the negative lead of meter. It is still worth checking/testing even though all are connected via a gnd strip - maybe the contact for bulb to the GND strip is bad. However as other bulbs work it is likely to be in the feed to reverse lamp and most likely is a faulty reverse switch as someone else posted but not conclusive yet until you test it out and you may find a bad connection somwhere else. Typically motorhome builders extend the wiring for the rear light if a coach built as they increase the rear length. Look for this additional wiring extension and connections and check then out. There is more likely to be a failure there than in the reverse switch itself. Jon. p.s. And do check the connections through the plug to the cluster as well, they are not always very waterproof as the wiring is loose into the rubber boot on some and water can get in. I am assuming a coach built here not a van conversion. Link to comment Share on other sites More sharing options...
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