Alright guys, a few weeks ago, my rear window defogger stopped working. I have an idea of the cause, but still require a push in the right direction.
Problem:
Rear window defogger not functioning on my 1999 Golf MK4 1.9 TDI with heated mirrors.
Context:
This might have started roughly around the same time one of my heated mirrors came loose and was replaced (bacause some ** drove/walked/cycled into it), but not entirely sure this relates to it.
Also, this could be the mind playing tricks with me, but it seems that when the switch is turned off and instrument lighting on, the light in the switch is brighter than before. When the switch is activated, it still goes a lot brighter.
Assessment so far:
Preliminary conclusion:
The component providing power to the heating grid seems to be underpowered, given the low measured voltage and the voltage drop upon connecting. Now this looks more like the behaviour I would expect from a transistor and not from a relay. So this doesn't fully add up.
Question:
Is there indeed a relay in between or other electrial circuit? (I would expect so, no one is his right mind would make these 120W go through that plastic switch I guess..) If so, is it in the relay panel in the compartment above the panels or somewhere else? And any tips on how to assess it?
Many thanks for the insights!
Problem:
Rear window defogger not functioning on my 1999 Golf MK4 1.9 TDI with heated mirrors.
Context:
This might have started roughly around the same time one of my heated mirrors came loose and was replaced (bacause some ** drove/walked/cycled into it), but not entirely sure this relates to it.
Also, this could be the mind playing tricks with me, but it seems that when the switch is turned off and instrument lighting on, the light in the switch is brighter than before. When the switch is activated, it still goes a lot brighter.
Assessment so far:
- With the switch on, checked voltage over the grid: 0V.
- With the power off, checked the resistance of the grid: 1.2 Ohm (which at 12V would imply 10A and 120W heating, which is the ballpark I'd expect)
- Checked incoming voltage at the defogger switch (pin 5): 12V.
- Checked connectivity of the switch (between pin 5 and 6): Works as it should. 0 Ohms when switched on, no connection when switched off.
- With the terminals of the grid disconnected at the tailgate, checked voltage at the tailgate terminals: 8.1V, which after connecting drops to 0V again.
Preliminary conclusion:
The component providing power to the heating grid seems to be underpowered, given the low measured voltage and the voltage drop upon connecting. Now this looks more like the behaviour I would expect from a transistor and not from a relay. So this doesn't fully add up.
Question:
Is there indeed a relay in between or other electrial circuit? (I would expect so, no one is his right mind would make these 120W go through that plastic switch I guess..) If so, is it in the relay panel in the compartment above the panels or somewhere else? And any tips on how to assess it?
Many thanks for the insights!