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Fuse blowing and horn sounding issue, wont crank

B

bonus99

Shifting Up
Hello,
I was hoping for some guidance on an electrical issue, let me explain...
I have recently taken ownership of a 110 CSW 300tdi.
I was checking out the lights as I thought the rear left tail light had blown and it turned out to be a fuse. I put another fuse in and it was OK until I cranked the engine and then the fuse blew again. I had worked out that if I cranked the engine and then turned the lights on, then the fuse would not blow but. this was short lived.

I checked the earth at the rear and it was secure, therefore, I suspected a short somewhere. The tow hookup was sodden and rusty and i just ripped out that wiring back to the right hand side rear light terminations to rule that out.

Now the bad bit, having run out of both 5 and 7.5 amp fuses and in a moment of short sighted madness (literally) I put a 20 amp fuse in the LH tail light socket instead of a 2 amp (both clear in colour). There was a chattering of a relays and then the horn continually sounded for a few seconds before i pulled off the negative from the battery, which was very loose as I was testing and kept removing it.

I stripped out all the dash as I wanted to make sure there were no shorts etc and it has to come out anyway as part of the cleaning and repairing. After a series of tests and checks, I am now in the following position.

LH fuse still blows after a short amount of time, possibly indicating water ingress somewhere?
I believe that the beige relay to the right of the red relay on the right hand side of the steering column is the Alarm relay? With this pulled, the horn does not sound, all electrics appear to work but the engine does not crank. With this in, the horn sounds unless I put the lights on. Engine will not crank.

I have searched the forums and there are a series of similar issues but nothing that seems to match mine.

I would be grateful for any ideas on where I go from here?

Thanks
Bruce
 
You might have blown your alarm relay as to much power went to it. As for your fuse issues take out your l/h tail light and check it’s condition, make sure it’s not corroded and earthing out as a lot of water ,salt and 💩 gets to this place. Check out the wiring from this area back to the front. You might have a damaged wire under your body that you haven’t noticed. Also check all other fuses just to be sure. Good luck and let us know how you get on:thumbsup:
 
Having a fuse blow when you crank the engine almost suggests that the earth from the starter (engine) to the battery (chassis) is bad...
For starters, (with any vehicle that you are unfamiliar with the service history) you could do worse than check and clean all the battery and chassis connections that you can find. Its an easy(ish) job and will prevent (or cure) all kinds of weird problems. Wire brush, new bolts/screws and loads of vaseline on them.
 
Worth having a crawl around underneath and tracing the harness routing to make sure its not got pinched or damaged.
Has any welding been done on the chassis? the wiring harness runs through the chassis and can be damaged (melted) if whoever was doing it didnt take precautions. This can cause weird, possibly intermittent problems.
 
Thanks for the replies. I did check out the lights and they looked ok but will swap sides to see if the fault follows. I will do some reading on the alarm immobiliser, not sure how it operates. Also will check the earth's. It will be next weekend now but I will let you know how I get on
 
Hello again...
Its been weeks since I have been able to get out due to the weather and family commitments. I have gone over it again today and as well as the car not cranking, the horn sounds when the lights are put on and eventually the fuse blows for the left hand lights. I bought an ODB2 reader but I don't think the alarm plug is ODB2 compliant.

I have all the dash out and the wiring seems OK and free from water ingress etc. The wiring at the back is all good and I have removed the water logged tow pack wiring. Battery cables and earths seem to be fine.

Given that the alarm is problematic anyway, I would probably have all the existing alarm and immobiliser out and replaced with a decent aftermarket alarm, any comments on this route would be welcomed as this seems to be the easiest thing to do. I was not planning to spend on an alarm but I have the budget.

Other than that, I could be at this for weeks with the time that I have and would welcome any recommendations for an experienced defender electrician or enthusiast that is local to Heathfield, East Sussex (TN21) that I can pay to fix it or get me going in the right direction.

One thing that I don't understand is this, it was starting before I put the wrong size fuse in the lights, I would have thought that would just affect the wiring for the lights and I do not see how it could have interfered with the alarm.

Hopeful of your suggestions, after wanting a Defender for 3-4 years I now have one under my nose that I cannot use :(

cheers
bruce
 
Did you check all the earthing points? I think you need to remake the connections (remove the earth cables, clean to shiny metal cover in vaseline to protect the metal and replace the cables). chech the circuit diagram, but you will find some on the bulkhead and near the rear lights, and make sure the main grounding cables between the battery-chassis-engine are OK. Until you verify these you are going to spend time chasing problems elsewhere when the fix may be relatively easy.
 
mikeau said:
Did you check all the earthing points? I think you need to remake the connections (remove the earth cables, clean to shiny metal cover in vaseline to protect the metal and replace the cables). chech the circuit diagram, but you will find some on the bulkhead and near the rear lights, and make sure the main grounding cables between the battery-chassis-engine are OK. Until you verify these you are going to spend time chasing problems elsewhere when the fix may be relatively easy.
Click to expand...

Mike is spot on with this, check the earths thoroughly and you could do the old jumper lead from the battery earth to engine block to prove it quickly. :)
 
Thank you. I will go over the earth cables now as it is dry! However, having just been out to it, the horn sounds as soon as I connect the battery, unless I remove the beige alarm relay.
The fuse now pops as soon as I turn the lights on and I have disconnected every lamp.
 
I have made some progress... Having disconnected all cables to the back of the car, I was still getting a short to earth between the dash and the cable plugs under the bonnet where they join to the rear part of the cable loom. I was twisting and checking all the cables for shorts and the multi-meter diode check sounder kept going off. I traced it to a blue moulded cable junction thing behind the dash in the centre, when I move that, there is a short from the fuse position to earth. This thing does not seem to be a plug but looks like a giant scotchlok for many cables, I shall investigate further. this looks like it will solve the short problem and then I will have to look at the immobiliser issue. will update when i have more info
 
This appears to be the culprit
 

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although that is a mess, i'm not sure that its the sole problem as I am still getting a short from the fuse point to earth on both the LH and RH terminals. Its raining again and it will have to wait until next time. To be cont...
 
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