No power at master cylinder

[will t]

hi all, i have a recently acquired 1967 SO-42 poptop camper whose brakelights don't work, so after searching the split bus forum I started with checking for power at the master cylinder switch. with the pedal depressed there is no power at either terminal. I ordered a new switch and a new 9-pin from WW. Any thoughts? I am a rank amateur when it comes to wiring so your help and expertise would be greatly appreciated.

(btw, running lights, hazards, and signals work fine)

thanks,

will

[BulliBill]

First off, congrats on the new Bus!

Do you have a single- or dual-circuit master cylinder. A little way into the '67 model year VW introduced the new dual-circuit system for the Transporter (it has two brake light switches instead of one).

I am no electrical wizard either, but I'm pretty sure that whichever system you have, you should have power on one of the wires heading to the master cylinder switches. When the switch(es) engage, they complete the circuit to the outgoing wire to light the brake lights. See if you have power in one of the lines. If so, then I guess your switch(es) are at fault. Other things to check are good grounding of the taillight bulb holders to the body (many of us add a ground wire to ensure that this happens).

Out of curiousity, If your hazard lights function fine, why did you order the 9-pin relay from WW?

Bill Bowman
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Thanks for any help!

[74 Cosa]

Did you check the fuse? I believe it is the second fuse from the right.

[EverettB]

The master cylinder switch always has power at one terminal.... when the key is on.

If you are not getting power there, you need to check that wiring first.
Could be just the fuse as someone said above (easy fix)

Once power is going to the switch, you can make sure the taillights work by using a jumper wire across the 2 switch terminals.
Jump it and the lights should go on.

Lights work? Now you can check the switch.
Press the pedal and the taillights should go on.

If not, bad switch.
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[will t]

the fuse is good but there is nothing connected to it! should a wire go directly from there to one of the two master cylinder connections?

this camper is early 67, and doesn't even have back-up lights. i believe it was made in november but i'm not sure. vin is 237005386. it has a single-cylinder master.

i ordered the 9-pin because the PO said he thought it was not so good. he could easily be mistaken but i thought for 60 dollars to know that part was good it made sense.

thanks!

[olliehank47]

[will t]

you all are the best. i found that the black and red wire to/from the master cylinder was on the wrong fuse terminal. i put it where it belonged, no brake lights. so i jumped the two master cylinder terminals together and voila! brake lights. so, i will replace the switch when it arrives.

thanks!!!

will

[EverettB]

[busdaddy]

Ummm.....just to make things clear you do have the key turned on when testing the brake lights, right?
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[will t]

thank you for the diagram. yes, there was nothing connected to the second fuse from the right. as i said, i found the black and red on another fuse and moved it and when i jumped the master cylinder the brake lights worked. however, i may not be completely out of the woods with another switch because there are supposed to be two more wires coming out of that fuse. looks like one wire goes to a circular thing with six wires total to it. i don't know what that unit is. the other (third) goes to post 15 on the 9-pin, it looks like.

will

[will t]

yes, key on to test anything related to brakes.

[busdaddy]

[olliehank47]

[BarryL]

[Eric&Barb]

BTW make sure to disconnect the wire going from the coil to the distributor points and condenser.

Otherwise if you leave the ignition switch on while testing, you can have the points burn up if they happen to be closed.
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[will t]

thanks for all the sage advice everyone. i'll have another look at things tomorrow. i may have damaged the points by accidentally leaving the ignition on for a bit. when i drove the van this afternoon something felt a little weird... i'll look at them as well.