Date: Sun, 8 Jun 2014 20:13:08 -0400
Reply-To: Mike B <mbucchino@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike B <mbucchino@CHARTER.NET>
Subject: Re: Brake Light Troubleshooting Tips?
In-Reply-To: <00dd01cf8373$2c6b9740$8542c5c0$@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
You won't get a brake warning light as long as the dual master
cylinder is still making brake pressure properly on both seals within
the internal dual-circuit piston.
If one brake light switch fails and the other one still works, the
brake warning light will not come on. If that was true, it would have
probably been on for a while now. If one switch failed, the other one
would still activate the brake lights all the way until that last one
failed also. Then you'd have no brake lights, at all, as they are wired
in parallel.
Jumpering one switch would not trigger the dash brake warning light.
The warning light on the dash is driven by the third terminal on the two
switches (early VW bug dual M/C brake switches only had two terminals
each). The third terminal goes to ground when the master cylinder
piston moves farther in the bore due to one or the other piston seal
failing, not due the the brake lights not operating.
It's really not hard to reach the master cylinder and brake light
switches, if you pull the entire instrument cluster, which is not very
hard to do. Just be careful of the plastic mounting tabs, as they get
very sun-baked and brittle at this age.
Start at the fuse and check for voltage that goes into one side of
each switch, then out of the other side when you apply brake pressure.
If that all checks out ok, then the wire traveling back to the
tail-lights is open somewhere, possibly due to corrosion in a connector
at some point.
I doubt that both brake switches are failed.
Mike B.
On 6/8/2014 7:41 PM, Stuart MacMillan wrote:
> They can both fail, it happened to me on my '84. Pull the wires off the
> switches and jump the pairs with wire or paperclips (ignition on) to see if
> your brake lights work. Jumping a single pair should trigger the brake
> warning light. Easy to replace without bleeding the system, just put a rag
> underneath.
>
> Stuart
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Steve Williams
> Sent: Sunday, June 08, 2014 12:16 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Brake Light Troubleshooting Tips?
>
> I hope you have tips to help me troubleshoot my brake lights. '84 Westy
> Wolfsburg.
>
> Symptom: No brake lights. No brake warning light, either.
>
> A local VW shop worked on this a few weeks ago. They checked the brake
> light switches and found no problem there. They believe the problem was due
> to a backup warning system that had been spliced into the left taillight
> wires (ground wire and reverse light wire), so they removed the spliced-in
> wires, leaving the original wires chewed up by the cheap-o splices.
>
> The reverse lights, taillights, turn signals, and side markers all are
> working fine, but I went ahead and repaired the chewed-up wires (solder and
> heat shrink), and the reverse still lights work fine. I don't think it's a
> problem with that ground wire, which serves the whole assembly.
>
> With the brake pedal held down by a piece of wood, there's no power on the
> brake light wire at the left or right taillight assembly.
>
> Fuse #8 is intact and has power on both sides.
>
> That fuse originally served the interior lights and cigarette lighter.
> The GoWesty aux battery kit removed those from the fuse, leaving just the
> "stop lights" (as they're called in the Owner's Manual). I installed that
> kit years ago, and the brake lights were working until recently.
>
> I have not checked the brake light switches myself. I think they'd have to
> BOTH fail to get no brake lights AND no brake warning light, right?
> Is it hard to get in there and get a voltmeter on the brake light switches?
> I took a peek, but I haven't removed the instrument cluster yet.
>
> Thanks for your advice.
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