Headlight switch options:, Who's added an extra relay? Options

[Prospectfarms]

Quik search reveals HL switch a common point of failure.

Long NLA, I saw a late-model NOS selling for $285, which is less than the last OEM price. Way too much for me, and I have an early switch anyway.

Since the switches are prone to break down, it doesn't feel satisfying to replace it with a used switch that's likely to fail soon anyway. (Sorta like the MPS problem.)

The late Lapuwali suggested several times that a VW switch (@$40 OEM, $20 aftermarket) could be converted of 914. His reasoning was they functioned the same: 1 Off, 2, Non-keyed power to parking lights, etc., 3. Keyed power to headlights. His theory was that the Porsche switch internally ganged terminals while VW combined the wires before entering the switch and therefore VW switches had fewer connections. He proposed an adapter plate that spliced the proper terminals that could then be connected to the VW Switch. I couldn't find a thread where that had been accomplished

The other school of thought is to relay the headlight part of a functioning light switch, prolonging its life. This suggestion confuses me because my reading of the diagram is that the "combination relay" already does this. For instance, current for the headlights seems to be supplied from 56 on the relay via closing 56 on the ignition switch. In other words, the HL switch does not carry the headlight current. So why another relay?

Am I mistaken? Anyone done either modification? How?

[Prospectfarms]

AM (IMG:style_emoticons/default/icon_bump.gif)

[SLITS]

My suggestion is to use a "known good" used one.

There are two ...

Early is 10 pin

Later is 11 pin

Which do you need?

[Prospectfarms]

My suggestion is to use a "known good" used one.

There are two ...

Early is 10 pin

Later is 11 pin

Which do you need?

Thanks, SLITS, My '72 has 10 pins. So you don't think adding a relay to the headlight circuit is worthwhile? Again, given the OEM relays already in-place I can't visualize how it would help, but a bunch of folks have offered that advice in previous threads.

[SLITS]

Adding relays lessens the current through a switch. Old wiring also increases resistance and commensurately heat.

Since the switch has probably lasted 40 years, who knows how many cycles it has seen.

I am not one who works out the diagrams to add relays or use different switches. When I am forced to, I will do it, but for now I stick with used switches.

I don't think I have any 10 pin switches, but will at least look.

[Prospectfarms]

I can use either, so they say (jump the extra terminal to keyed power? Or something like that.) Thanks.

[arty914]

Hi, EBay has some listed even as I speak. Some early style some late. I've had good sucess with the ones I've purchased in the past. If your handy and not in a hurry. Pelican has a good article on rebuilding the little buggers. I'm not all that handy and I managed to follow the directions correctly. I wouldn't recomend changing the wireing.

[Dave_Darling]

Here's all you wanted to know about the guts of the early switch:

http://members.rennlist.com/pbanders/headl...h_internals.htm

--DD

[Prospectfarms]

Here's all you wanted to know about the guts of the early switch:

http://members.rennlist.com/pbanders/headl...h_internals.htm

--DD

Thanks Dave, I reviewed Brad Anders typically thorough how-to on disassembly and restoration of switch before I began this thread. The switch works with silver-plated sliding contact plates. Like any switch, the contacts are prone to corrosion and failure.

Brad's solution for corroded plates was to replace them with parts from another switch. I don't have a supply of used switches and those of unknown (internal) condition cost $25+. Since they are old, I'd at least like to know how to reduce or prevent the conditions that causes them to fail, before undertaking a rebuild.

That's behind the suggestions I found in older threads to switch the current they normally carry with a relay. I know that Jim Hoyland was interested in this, as well as several other's who claimed to have done it. Those posts are several years old, and I couldn't find any practical instructions.

I don't know how much current another relay would divert from the HL switch, since it looks as though the current for illuminating headlights are carried by the ""multi-purpose" relay on the fuse panel. I can't tell from the WD whether this is also true for the parking lights, but, judging from number of thread topics, that's the one function of the switch that seems least likely to fail. The current path is hard to trace though.

Substituting a VW switch is an attractive idea since they are still manufactured and sold. It looks the same, and the external operation is identical too. On my bus, its even in the same spot on the dash.I'm trying to figure out the source/ termination for the switch connections. It can't be exactly the same internally, because my bus does not have pop up lights and from the Porsche WD it seems that current for the headlights might be diverted through the headlight motor relays also. Confusing.

My hope is that some of those who've previously suggested adding relays to these circuits will step up with some information.

[Dave_Darling]

The headlight current does go through the high/low relay, but it goes through the headlight switch to get there. So it would probably be worthwhile to use a relay to reduce the current going through that part of the switch.

There's no relay in the engine bay light/instrument lights/license plate lights/etc. circuit. The instrument lights one comes out of the switch, through fuse 7, then back into it again to go through the dimmer (rheostat), and back out again to the lights. You could put a relay in before or after fuse 7 to offload that circuit.

The power to the headlight motors does not go through the switch, the switch triggers the relays that run the motors.

Power for the parking lights, under some circumstances, does go though the switch. There's no relay, but there are fuses, numbers 5 and 6.

I hope the above is of some use. The information in it comes from the 74 wiring diagram; the circuitry for the earlier cars is slightly different.

--DD

[Prospectfarms]

Thanks Dave, that does help. Ironically, the Pelican Tech page that also has Brad Anders switch disassembly article contains a follow up about late model switches. Apparently they separate the contacts for the head light illumination and head light motors: 56 and 56K.

There's no relay in the engine bay light/instrument lights/license plate lights/etc. circuit. The instrument lights one comes out of the switch, through fuse 7, then back into it again to go through the dimmer (rheostat), and back out again to the lights. You could put a relay in before or after fuse 7 to offload that circuit.

Got it. Feels much better to understand why that circuit is routed through the switch twice. Thanks again!

The headlight current does go through the high/low relay, but it goes through the headlight switch to get there.

Switch-relay-bulb. Borrowing terms from the ignition system, sounds like the headlight switch supplies the HT current to the relay and the hi/low switch sends the LT current. The relay choose which of two circuits to send headlight current depending on input from the hi/low steering column stalk ?

[Tom]

Stuart,
http://www.google.com/url?sa=t&rct=j&a...Y_sNLJ2R6peUaZQ
You can buy relay kits here and I think they have some electrical diagrams also explaining how to install. You will need to run heavy wire from the battery to the relays. I have seen discussions on here about installing relays for the high output headlights. One of the reasons some opted for the 6-way fuse block versus the 4-way. You may be able to find info at Bus Depot also.
Your turn signal stalk "toggles" the hi/low relay.
Tom

[Dave_Darling]

Switch-relay-bulb. Borrowing terms from the ignition system, sounds like the headlight switch supplies the HT current to the relay and the hi/low switch sends the LT current. The relay choose which of two circuits to send headlight current depending on input from the hi/low steering column stalk ?

That's the way I read the diagram.

--DD