91 Jetta (Mex) Headlight switch

Make sure those little terminals inside of the plug are clean and tight. Might be a problem there creating too much resistance = heat into the switch. just a thought!

AND are you putting in USED switches or NEW switches?

Could it be defective or loose wiring rather than the switch itself?

From my electronics experience at work, I used a very effective (palstic safe) electronics spray cleaner on the switch socket. I guess I could go in there with relay contact burnishing type-tools to try and "shine-up" the contacts.

(I once had a perhaps relevant problem on my "85 Golf with the wiring harness socket going to the main fuel pump under the car. I guess oxidation started, creating a "hot-spot" with all the current flowing through that point -> -> the heat took the "spring" out of the socket contact resulting in a "flaky" electrical contact. It caused the engine to hiccup when I drove over pot-holes, railroad crossings,etc. Trying to replace the original connectors was impractical $$$ so I cut the socket off and made my own.)

The switch I paid about $60.00 is new w/ VW sticker and all....

Thanks for the feed-back!

Everything is still suspect. I checked the wiring once and like most everything I do I'll probably end up going over my own work :-) at least once.

But I think it's still the switch. The failure mode is: Parking / Running lights-position, the Parking / Running lights always work. When I turn "on" the headlights sometimes the Parking / Running lights stay "on", sometimes not. Looking at the car's reflection in store front windows I see that when I turn "on" the headlights, the Parking / Running lights may flash once like there's a weak spot in the switch mechanism -- as I noted before if I sit there and fiddle with the switch a little I can find a point when everything is fine - if it'll only stay there while I'm driving.

I don't think it's wiring because both the "left"-side and "right"-side of the car have their own wires. If one side (either side) lighted and not the other I'd start checking the wiring starting from switch pins 58R and 58L. However, that doesn't seem to be the case. It's both R+L Parking lights "on" or "off" -- to me that points to the switch's innards.

Thanks for the ideas!

are these new switches? are these OE switches?

I've never had a problem with the switch personally, but here's a thought. The switch is directly connected to all the loads. You could be drawing substantial amperage. Overwattage bulbs could lead to even more amperage. I'd check to make sure you have the right bulbs and consider installing relays to power the headlights, that should reduce the load on the switch a lot. Its possible the amperage is causing heat which is causing it to fail.