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dag019

dag019

Well-Known Member
Posts
6,148
Location
Warwick
i have a couple of issues with my electrics currently which I am hoping are linked. I have a 300tdi bulkhead wiring loom with the white plastic connectors rather than the black bullets, the rest of it is new “original” 1889 110 wiring.

First problem is the headlight switch contacts have melted and sunk into the plastic causing the headlights to go off. I have temporarily built it backnup
With solder somit makes a connection as at this time of year the lights are quite important, but will order a replacement switch. However, I would like to fix the root cause to prevent it happening again. I believe the 300tdi has the headlights on relays already. They are only lit with the ignition on and there is a clicking from deep inside the dash when switches on which I am assuming is a relay activating. Therefore I am not sure the standard advice to fit a boomslang harness is relevant as for the switch to be overloaded the problem has to be with the relay switching side of the circuit rather than the headlight side of the circuit. Any suggestions of what I should check or common problems?

The second issue I have is with the indicators and I am hoping the two problem are linked in some way but am not holding my breath. This problem is intermittent so is difficult to replicate but occasionally when indicating (only left, right works perfectly) the indicators are very dim and the trailer light flashes every time indicating there is a huge increased resistance in the circuit. I have checked and cleaned the bulb holders but this has made no difference and will check the earths when I get a chance but know the rear to be good. Again any suggestions of likely causes and obvious things to check?
 
dag019 said:
i have a couple of issues with my electrics currently which I am hoping are linked. I have a 300tdi bulkhead wiring loom with the white plastic connectors rather than the black bullets, the rest of it is new “original” 1889 110 wiring.

First problem is the headlight switch contacts have melted and sunk into the plastic causing the headlights to go off. I have temporarily built it backnup
With solder somit makes a connection as at this time of year the lights are quite important, but will order a replacement switch. However, I would like to fix the root cause to prevent it happening again. I believe the 300tdi has the headlights on relays already. They are only lit with the ignition on and there is a clicking from deep inside the dash when switches on which I am assuming is a relay activating. Therefore I am not sure the standard advice to fit a boomslang harness is relevant as for the switch to be overloaded the problem has to be with the relay switching side of the circuit rather than the headlight side of the circuit. Any suggestions of what I should check or common problems?
Click to expand...
I'm not sure, but I suspect on my 300Tdi (1996) the only original relay in the circuit was a dim-dip relay. I think the full current still goes through the switch on the 300Tdi loom. Years ago I had to replace my switch as it melted. Recently, I fitted a boomslang primarily in the hope that it would give me a bit more brightness, but also to save the load on the switch as at the time that was the claim. ie the root cause of the melting switch being bad design because of the current flowing through it.
 
Al2O3 said:
I'm not sure, but I suspect on my 300Tdi (1996) the only original relay in the circuit was a dim-dip relay. I think the full current still goes through the switch on the 300Tdi loom. Years ago I had to replace my switch as it melted. Recently, I fitted a boomslang primarily in the hope that it would give me a bit more brightness, but also to save the load on the switch as at the time that was the claim. ie the root cause of the melting switch being bad design because of the current flowing through it.
Click to expand...

I would agree that the only relay (concerned with the headlights) behind the binnacle should be the dim-dip. If it’s clicking with the lights turned on, I would suspect it to be broken. I stripped mine, gutted it, and soldered a 2.5mm link wire across the terminals.

As for the switch melting. This is probably down to a higher than normal current. Either higher wattage headlights or a poor connection. Check all your earths, especially the two on the wings, and check your headlight connections. See what voltage you have at the bulbs with the engine running and headlights on. If it’s below 12V, you may well benefit from fitting a Boomslang harness.
 
Ok so headlight solution seems to be a boomslang loom and a dimdip bypass. That should be straight forward enough. Will just need to look up what the dimdip looks like and where inthe dash to find it. I am guessingthough if that is the problem that will have nothing to do with the indicators so still need to work out what is going on there.
 
dag019 said:
Ok so headlight solution seems to be a boomslang loom and a dimdip bypass. That should be straight forward enough. Will just need to look up what the dimdip looks like and where inthe dash to find it. I am guessingthough if that is the problem that will have nothing to do with the indicators so still need to work out what is going on there.
Click to expand...
I never touched my relay. just put the boomslang harness in. My lights were working fine at the time though.
Not sure of they are all the same, but 4th post down in this thread LINKY
 
dag019 said:
Ok so headlight solution seems to be a boomslang loom and a dimdip bypass. That should be straight forward enough. Will just need to look up what the dimdip looks like and where inthe dash to find it. I am guessingthough if that is the problem that will have nothing to do with the indicators so still need to work out what is going on there.
Click to expand...

From what I have read, it’s easiest to disconnect the large resistor mounted on the drivers side inner wing, than it is to modify the relay like I have.

If you know what your doing with wiring, you can make a harness that does the same as the Boomslang.

As for the indicators, check the earths as I said before. You may be surprised.
 
mick 1986 said:
From what I have read, it’s easiest to disconnect the large resistor mounted on the drivers side inner wing, than it is to modify the relay like I have.

If you know what your doing with wiring, you can make a harness that does the same as the Boomslang.

As for the indicators, check the earths as I said before. You may be surprised.
Click to expand...
I've often wondered what that was for :eek: Put a post on about it years ago, but nobody knew at the time.
 
Last edited:
Headlights fixed temporarily again! Failed completely on the way home. Turned out to be the dim dip relay. Worked when it was bypassed, so made a permenant bypass out of the old one following this guide (link) similar to @mick 1986
If the failing dim/dip likely to be the cause of the switch overloading? I am going to get a new switch and a boomslang harness. But wondering if I still have a problem somewhere or if the relay bypass will have solved it.
 
mick 1986 said:
Check all your earths, especially the two on the wings
Click to expand...

Still not solved the indicators issue. So Unfortunatly but unsurprisingly was not linked to the headlights. Where are the earths on the front wings? I have tried to trace it back from the light fittings but the earth just disapears into the main loom. I was expecting a ring connection attached somewhere similar to what is found on the rear loom.
 
dag019 said:
Headlights fixed temporarily again! Failed completely on the way home. Turned out to be the dim dip relay. Worked when it was bypassed, so made a permenant bypass out of the old one following this guide (link) similar to @mick 1986
If the failing dim/dip likely to be the cause of the switch overloading? I am going to get a new switch and a boomslang harness. But wondering if I still have a problem somewhere or if the relay bypass will have solved it.
Click to expand...

I’m not sure if it’s likely to be the cause, I suppose it could be if it failed in such a way as to cause current to leak from the live to the earth. Thinking about it, if the coil has broken down, it’s possible to be the cause.

If you have shorted it out, keep an eye on the switch contacts to see if you get an early warning of them failing.
 
dag019 said:
Still not solved the indicators issue. So Unfortunatly but unsurprisingly was not linked to the headlights. Where are the earths on the front wings? I have tried to trace it back from the light fittings but the earth just disapears into the main loom. I was expecting a ring connection attached somewhere similar to what is found on the rear loom.
Click to expand...

Just read back through your indicator fault. Check the two side repeater bulbs, swap them over too. A few years ago, I replaced both side repeater bulbs for LEDs. This failed miserably and illuminated all indicators regardless of which way I indicated (hardly surprising). I swapped back to my original bulbs and tried again. Indicated right, bright lights and all good, indicate left, dim lights and trailer light flashing. Found the filament had blown and shorted the bulb, resulting in both sides being illuminated and dim. It may not be the case, but that’s where I would start. Put your hazards on and walk round to see if all indicators are working.
 
mick 1986 said:
Just read back through your indicator fault. Check the two side repeater bulbs, swap them over too. A few years ago, I replaced both side repeater bulbs for LEDs. This failed miserably and illuminated all indicators regardless of which way I indicated (hardly surprising). I swapped back to my original bulbs and tried again. Indicated right, bright lights and all good, indicate left, dim lights and trailer light flashing. Found the filament had blown and shorted the bulb, resulting in both sides being illuminated and dim. It may not be the case, but that’s where I would start. Put your hazards on and walk round to see if all indicators are working.
Click to expand...


Many thanks I will give that a check the side repeaters are definitly working when the indicator are working but that does not mean they are not the cause. I have not checked and cleaned them out like I have the other bulb holders.
 
Hicap phill said:
Earths on front wings should be loop & go to inner wing. 1 for each side. These go back to loom,earth to bulkhead
Click to expand...

I will try and have a better look but couldn’t see anything on the inner wing. That is what I was expecting! They all have the screw earth in the holder. And the screws are all stainless so that should be an ok earth in as much as the body screw earthier are.
 
dag019 said:
Many thanks I will give that a check the side repeaters are definitly working when the indicator are working but that does not mean they are not the cause. I have not checked and cleaned them out like I have the other bulb holders.
Click to expand...

Try the hazards first. It may show up the culprit a bit quicker.

If you have a trailer socket, and it’s easy to get access to, disconnect the power for the indicators. It’s another thing that may be the issue.
 
mick 1986 said:
Try the hazards first. It may show up the culprit a bit quicker.

If you have a trailer socket, and it’s easy to get access to, disconnect the power for the indicators. It’s another thing that may be the issue.
Click to expand...
The trailer socket is in in good condition. It is used regularly and is kept clean and oiled because of this so this should not the an issue. But if I still cannot find the problem I will try this.
 
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