Brake Light Switch Failures

[Ahwahnee]

For the second time in 3 years I have blown out both hydraulic brake light switches on my 84 Vanagon.

I am using the higher-wattage brake light bulbs available from a Samba member and also have a 3rd brake light that is a strip of 24 LEDs.

Seems like the thing to do is add a relay as I really like the brighter brake lights. Anything here I'm missing?

Also -- any idea why there are two switches when lights will work even if one has failed? Perhaps the 'brake' light on the dash fails to illuminate if one has failed (don't recall)?

Having 2 switches and thus 2 sources of power somewhat complicates the wiring of the relay (haven't really thought that through) unless I pick up on a point in the harness where the power is down to one wire.

Finally -- for the benefit of future searchers who are sometimes unsure where these swtiches are or how to get at them: Undoing the electrical connections on the left side of the dash and undoing the speedo cable from the back of the head allow the instrument cluster to be lifted well out of the way reveling the two switches:

The the switches themselves can be swapped with the loss of only a few drops of brake fluid and no need to bleed (in my experience).

[Vanagon Nut]

re: swapping switches.

My recent new MC install on my '88 shows that the reservoir cap vent hole is recessed in the fluid level connector. Tape that and reduce brake fluid flow? (as one would on old style cap)

On my '81 I had a plug contact failure. In my case, the wire fell out and was shorting to ground. Nice.

I imagine you checked, but are the contacts 100% ?

And maybe I'm misunderstanding your question, but my guess is that b/c the hydraulics are dual circuits thus there are two chambers in MC, if one circuit fails, other still lights up brake lights?

Just a WAG w/o Bentley in hand, but maybe the two switch wires converge at a connector in dash area? A relay would certainly make sense if parts quality is the issue.

Neil.

_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[Altoona]

Are you sure the switches are failing electrically, not hydraulically? I have a hard time believing that some higher wattage bulbs would cause the switches to burn out that fast, given the intermittent nature of brake usage. What is the state of your brake fluid? If the first set failed because they were gunked up with junk (common) and you changed the switches without flushing your fluid, it may have just gunked up the second set quickly. Just a theory though.

If you are set on the relay idea, the switches share a common source of power (red/yellow from fuse , they are just jumpered from one to the other. But this would have zero effect if the cause is hydraulic and not electrical in nature.

[Ahwahnee]

I tested the switches with an ohmeter and neither shows continuity when the pedal is depressed. I don't know how one would know whether this is "hydraulic and not electrical in nature" as I think the results would appear the same.

I did jumper the contacts on the plugs and the brake lights came on as they should.

I don't think a relay on the red/yellow would provide any relief as that would still put the full current draw through the switches.

I will look for a common point where those 2 red/black wires come together.

Oh yeah, my brake fluid is clean and refreshed regularly.

[Altoona]

Sorry, meant Red/black. They too are just connected together under the dash.

[AtlasShrugged]

I think the reason for two switches is redundancy..if one switch fails you have another..same deal with the dual diagonal brake system.

Having two functioning brake light switches does not increase the electrical load on the contacts..actually it significantly reduces the load on both switches contacts.

Very odd that both switches would fail at the same time. Be sure and replace both switches even if only one is defective.

Some of our aftermarket switch gear has been a real pain. Try and find some German made (not boxed in Germany) switches.

Try the NAPA switch part number ATM 113945515H from the old Altrom inventory. $8.50 and most likely German.

The additional current draw on the higher output bulbs is still fractional..it really should not be burning out your switches.

Porsche used the same brake light switches and they never changed even when they went to a third brake light in the back. A 50% increase in load.

[Ahwahnee]

[AtlasShrugged]

I think you may be over engineering. A 25 watt 12 volt bulb (stock 1157 bulbs are about 21 watt on the brake light filament) only draws 2 amps. Two bulbs and your LED strip you are pulling about 5 amps.

5 amps is very low and hardly needs a relay.

I think you just got a bad bad brake light switch.

There is not a warning bulb for a failed brake lamp switch or failed bulb(s) on a Vanagon.

Rather than a relay, if you are concerned about current draw. Run a 1157 LED brake lamp bulb. It only draws 3 watts and is very, very bright. I have one on my old motorcycle. Very durable.

See the link:

http://www.superbrightleds.com/moreinfo/led-vehicl...nAodA1sACw


With two of these LED brake lamp bulbs you now have .5 amps (6 watts) rather than 4 amps (50 watts) drawing across your brake light switches.

[crazyvwvanman]

80-84 switches have an extra wire. This is supposed to trigger the brake warning light module on the dash cluster, to warn you if half of the master has pressure and the other half doesn't. Beginning in 85 this was dropped, and a fluid level float switch was added to the reservoir cap instead. The later pressure switches have only 2 pins instead of 3. The dash wiring changed slightly for this with 85, and the brake warning light module changed as well.

Mark

[Ahwahnee]