2004 xc70 intermittent multiple high/low bulb failure

[aaronlife]

I noticed last year that both headlights started going out randomly regardless of high/low position.

If I wait, they will come back on. Or, if I switch the headlights off and then back on (or daytime to on) they work.

When they go out I get a multiple bulb failure warning on the dash. Otherwise it normally has the position light failure while the bulbs work. Any ideas? I looked for bad connections, but nothing obvious.

I was hoping the headlight switch reset method for getting my lights back on would be a clue. Does switching off and on charge a ballast? Does it reset a relay? If I wait 5-15 seconds it usually fixes itself.

What would take out both high/low left/right simultaneously?

Thanks in advance for ideas (I will revisit wires and connections as I recall was suggested last year, just wondering if the switch reset suggests something else. I can’t see fuses being intermittent).

[jonesg]

never had that problem but it sounds like a common ground or feed problem.
People have had trouble with the switch.

[aaronlife]

Ok tnx

[scot850]

I went through this recently with an 02 XC70 belonging to a friend. One headlight bulb went out one day and the other the next. After checking all the way through the system because of my error, it turned out it was both low beam bulbs. In this case the high beams were fine.

There is not much to the circuit and the headlights are fused separately on left and right.

The headlight switches are known to fail with age. The only other thing is the shunt(relay) under the dash. I recently wrote a note on this.

The last item is the high/low beam switch on the steering column. They can wear out.

Last is a bad earth somewhere as advised by jonesg above.

Last thing. My buddy who is an ex-Volvo mechanic (and P2 owner) says the connector on the back of the headlight bulbs for the low beams do tens to melt when the connectors get oxidized and then it makes the connectors run hot and melt the plastic.

Neil.

[aaronlife]

Thanks for all that, weather is warming up this weekend I will look it all over again. It’s subtle whatever it is because most of the time it works.

[aaronlife]

Interesting update, just now it was only the passenger high/low that went out. Came back on when i switched lights off/on.