Spotlight fuse keeps blowing????

Submitted: Sunday, Aug 17, 2003 at 14:11
ThreadID: 6639 Views:11265 Replies:7 FollowUps:2
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Just fitted a pair of Hella 4000 to a new TD Prado about 5 days ago. Lights worked a treat for a few hours the other night. Went to use them again last night and after I showed the missus where the isolation switch was she switched it off and on again a few times to see the difference of light up the road. This had the effect of blowing the 30 amp fuse. I replaced the fuse, bang, blew straightaway again. The relay (hella 30 amp relay) is still working with high beam (can here it clicking with highbeam going on and off). Any suggestions as to what may be causing this problem?
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Reply By: ToyMotor - Sunday, Aug 17, 2003 at 15:15

Sunday, Aug 17, 2003 at 15:15
Without wanting to be facetious (honest) - excessive current is causing the problem. What is the wattage of the spotlights? If 30A is the correct fuse to use, one troubleshooting method would be isolating the lights one at a time, and work back from there. Get more fuses, and keep changing them, until you've found the short. DON'T use a nail for the fuse, or you'll definitely find the problem (it'll be where the fire starts...)

Good luck!
AnswerID: 28193

Follow Up By: pilbaralad - Sunday, Aug 17, 2003 at 16:08

Sunday, Aug 17, 2003 at 16:08
The lights are 100 watts each. I am assuming a 30 amp fuse as the relay is 30 amps, (I didn't check the amps on the first fuse to blow)
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FollowupID: 19513

Follow Up By: ToyMotor - Sunday, Aug 17, 2003 at 16:16

Sunday, Aug 17, 2003 at 16:16
OK, a 100 watt light will draw about 8 amps, give or take. The 30 amp fuse might be a little excessive, but I wouldn't worry too much about that - there's a fair surge on switch on of cold filaments, so I'm using a 25 amp fuse for one 120W and one 100W light. The 30A rating for the relay is its contact rating, which you are not exceeding, so all is well there. Try disconnecting things one at a time, such as each light in turn, to see if the short goes away. If the fuse still blows with both lights disconnected, could be a wiring short to the body, or a faulty relay (almost impossible if it's plastic cased)

Good luck!
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FollowupID: 19516

Reply By: Mulga Bill - Sunday, Aug 17, 2003 at 16:20

Sunday, Aug 17, 2003 at 16:20
How about you get two new globes (needed for your first trip anyway) and put them in. Might be that one or both is eating amps on start up - a malfunction of sorts. Otherwise, maybe the globes are just a little hungrier than specced - up the fuse a bit ? Get me outa these suburbs !
AnswerID: 28196

Reply By: howesy - Sunday, Aug 17, 2003 at 16:30

Sunday, Aug 17, 2003 at 16:30
They are on the right track sunshine. Some lights can draw huge current and if the earth is average as well then the resistance is huge and resistance causes heat and bang. I have seen cases where over time even the relays start to stick on because of the draw and heat factors.
Buy another relay and jumper from the other one for the earth and activation wires and give it it's own feed to the other light and it's own battery feed with fuse. A 20 amp fuse should be all you need with this set up and I promise you will never have another problem
AnswerID: 28200

Reply By: Williewags- Sunday, Aug 17, 2003 at 18:39

Sunday, Aug 17, 2003 at 18:39
Being electrically challenged( haha I like that definition ) I have nevertheless deducted that all my light and spottie troubles come down to bad earthing. Make sure you have a good earth for your lights.
Cheers,
Willie

Gunbarrel Highway.

Always going somewhere
AnswerID: 28213

Reply By: sean - Sunday, Aug 17, 2003 at 22:25

Sunday, Aug 17, 2003 at 22:25
I have 4000's and have never had any problem but L have just completely rewired the setup on my new car as the wiring it came with was poorly done.

The 4000's should be wired baack to the battery earth and the standard light harness is set for this with the 2 wires coming out of each light. The isolation switch should also be wired into the relay earth and not the power from the high beam if this is not the way it has been set up.

Sounds like you have a short in the power to the lights or possibly inside the light itself. Its easy to unplug each light so you should be able to isolate the problem.

Sean
AnswerID: 28252

Reply By: JackLivesHere - Monday, Aug 18, 2003 at 18:22

Monday, Aug 18, 2003 at 18:22
Earth, Earth, Earth.
Had a similar problem with my lightforce a while back. Started from scratch and soldered all connections and earthed the lights correctly and not done a bulb or fuse in years.
AnswerID: 28328

Reply By: Eric - Monday, Aug 18, 2003 at 21:44

Monday, Aug 18, 2003 at 21:44
Pilbaralad.
The globes in any high powered lamp are almost a short cct when cold, that is why the electrical engineers that disign the factory looms for the head lights use a very specific wire gauge to limit the current but still give 12volts at the light, if you use the same gauge as the factory head lights ie about 2 mm you problem will be solved and your lights will last the life of the vehicle, Eric.
AnswerID: 28369

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