High beam voltage fluctuating between 15 and 0

[marius.dascal]

Hi guys, just installed a pair of led bulbs in my dipped beams , only got one side fitted as the other turned out to be a different fitment(for reason I don’t know) and after setting off to go home thinking the error in the dash was the new bulb I find out it’s my high beam bulb(another led). I thought maybe I might have moved something but no after checking and unplugging and re testing it was not coming back. Keep in mind this is only one side and the other high beam is working. I then took my multimeter turned the high beams on and tested the voltage, at certain points it was saying 15v were on the line and then dropping back down to 0 and back up . While the other beam was on with no issues. I tried different bulbs even going back to halogen and then I tried testing the voltage with no bulb in at all and same story. What is going on please god let somebody know about this bizarre issue. Also I should add I have checked the fuses and they all seem ok. I’ve had issues with fuses melting before and taking down half of the cars lights with it but that was not only one bulb.

[Cuprabob]

My guess is the control module is shutting the circuit down due to the current not being within expected values. When you switch on the ignition the diagnostics energises the circuit briefly and if, the current drawn is not that of a 55w bulb it will suspect a fault and shut the circuit down. Therefore if no bulb is fitted or an LED without the appropriate parallel resistor is fitted the circuit will be shut down.