Itinerant Air-Cooled

Hi All
Going slightly crazy with my rear lights on my 1970 bus. Indicators work, brake lights work, and front lights but no rear. Earths seem clean and tight, and obviously has power to rear!! Been working through this, to no avail. Would appreciate any help!!

Thanks Dave

Hi Ausdingo, and welcome!

Perhaps this will be moved to it's own dedicated thread soon, but in the mean time, could you fill us in a little more…

Is your bus a "USA-spec single bulb tail lamp" bus, or a "Euro-spec dual bulb tail lamp?"

Let's define the rear lights as:
A) parking lights. These should come on with the first click of the headlight switch, and stay on to the second click of the switch.
B) brake lights. These come on with the key on and the brake pedal applied.
C) turn signals. These come on with the emergency flashers or key on/turn signal switch activated.

Which lights are you missing?
Robbie

Ausdingo wrote: ↑

Wed Apr 24, 2019 6:05 pm

Hi All
Going slightly crazy with my rear lights on my 1970 bus. Indicators work, brake lights work, and front lights but no rear. Earths seem clean and tight, and obviously has power to rear!! Been working through this, to no avail. Would appreciate any help!!

Thanks Dave

Hey Robbie, I field the single bulb style because I don't own one, and you can field the dual bulb style, because you don't own one ....
Indicator and brake lights use the same 21W filament inside of the dual filament bulbs. The taillights use a 5w filament.
Each taillight goes to its own fuse, by law. If both taillights are out but the license plate works, I am going to suggest that you swap the dual filament bulbs out and be very very mindful of the bayonet pins in the bulbs. They must be correctly oriented to the slots in the sockets. This is how we get the correct terminal onto the correct bulb filament.
The bayonet pin closest to the bottom of the bulb goes into the deep slot. The bayonet pin closest to the glass goes into the shallow slot. Look inside the socket to make sure the terminals are both sprung towards you so that the bulb presses on both as you install. Got Bentley electrical diagram?
Colin

Thank you for the welcome Robbie. These are US tail lights, and the blinkers work and brake lights. The parking light (first click) and main lights do not come on. The front lights are working fine.
Thanks Dave

Hi Dave,

Your parking light circuit sounds suspect. How are your skills with a volt meter? Do you have 12v at either bulb tab in the socket when the headlight switch is pulled one click? Two clicks? You could also use a 12v automotive test lamp if you have one. If voltage is found, you have a bulb reach or contact problem. If no voltage at either with the switch pulled, keep reading…

Familiarize yourself with the Bentley manual wiring diagram, available in your Bentley manual. Or online here: https://www.thesamba.com/vw/archives/info/wiringt2.php



Since you're new, I'll let you in on a little secret… The 1970 wiring diagram fuse box (S) is upside down, yeah I don't get it either.

Let's look at the path the electricity takes from start to finish:
- Battery (A) to starter (B)
- Red wire from starter #30 to (E1) headlight switch #30
(We assume all this is good, because the headlight switch works otherwise.)
- White (grey?) wire from headlight switch #58 to buss bar for fusebox (S) slots 1 and 2. (On the RIGHT side of the diagram, LEFT side of the bus!)
- Through fuses to grey w/red and grey w/black wires.
- Grey w/red and grey w/ black wires #58 on tail lamps (M9 and M10.)
(This is where the bulbs live, we want to assume the ground path is good, because the high-output side of the bulb works. Clean your grounds anyway. )

Each of those places should have 12v with the headlight switch pulled one or two clicks. You can go through them one-by-one if you'd like a nice tour of your electrical system where you can clean and snug all the connections. Of course you are welcome to check the fuse box for good, clean 8-amp white fuses first. Make sure the ends of the fuses are nice and pyramid-like. No snow-cone round fuse edges, those belong in the dumpster.

Let us know what you find!
Robbie

PS- Colin, I'll give my hypothetical dual-bulb diagnostic once we solve this one. :)

Thanks Robbie for that detailed replay. Very helpful. No worries on the diagram being upside down, thats how we walk back home!!!! I will give that a lash with a volt meter, and see what I find.
Thanks mate