300CE fuse problem

[Mer300]

300CE 1989 has had intermittent 5A fuse blowing that controls dash lights rear offside tail light and number plate light (number 3 I think). This was happening about once every 2 months but is now permanent. Happens when I switch on the lights. Have replaced all fuses and cleaned all connections. I noticed one time the offside headlight glowing brighter before the fuse blew. The bulb warning light is also on but this has always been on since I've owned it !

Any ideas?
Thanks
GT

 

[television]

300CE 1989 has had intermittent 5A fuse blowing that controls dash lights rear offside tail light and number plate light (number 3 I think). This was happening about once every 2 months but is now permanent. Happens when I switch on the lights. Have replaced all fuses and cleaned all connections. I noticed one time the offside headlight glowing brighter before the fuse blew. The bulb warning light is also on but this has always been on since I've owned it !

Any ideas?
Thanks
GT

You will only find the problem with an ohm meter , do not keep putting fuses in as you will damage the wiring and the fuse holders.

the fault will most probably be with on one the lamp holders where the insullation has crumbled away with the heat.

Welcome to the forum. Malcolm

 

[Mer300]

What should the resistance typically measure through this circuit? I assume close to zero ohms if all contacts good? Do I need to engage the relay to make this measurement or would that not happen since the fuse is out?

Thanks for any direction before I pass to the big bucks guys...
GT

 

[television]

The only way to measure the resistance, would be to take out all of the bulbs on that circuit that is blowing as the resistance is to low to measure with any meaning.

take a single 12v 21w lamp, that has a resistance of 21Ω, two would drop it down to 11.5Ω the lower the resistance the harder it is to get a sensible reading, as the contact need to be perfect.

Do not forget the the headlamp operate via a relay.


Malcolm