Hella 4000 Driving lights blowing fuses

Submitted: Wednesday, Apr 29, 2009 at 19:46
ThreadID: 68367 Views:4398 Replies:9 FollowUps:2
This Thread has been Archived
One for the electrically minded!

I have a set of Hella Rallye 4000 driving lights which I've been running for over 12 months now. They have been great lights and have had no problems with them until now.
About 1 week ago the lights dimmed and flicked but came good. However a few days they did it again and this time blew the 30A supply fuse.
No problem I thought - I haven't been really happy with the pre-made wiring loom I used and thought there may have been an intermittent short in these cables, so I rewired from the relay to the lights with heavier gauge (25A each) wire. Tested the lights - all working OK.
However last night the 30A fuse blew again after only a few minutes of operation.
Checked the relay, wiring and lights and everything seems OK. Measured the resistance at the lights which was 0.1 ohms which seemed low and has confused me. I am now suspecting the lights but both are the same and there is no obvious damage/problem.

Any suggestions or ideas to check? Any information most welcome.
Thanks,
Geoff
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Reply By: Member - Paul W- Esq (VIC) - Wednesday, Apr 29, 2009 at 19:57

Wednesday, Apr 29, 2009 at 19:57
One of 2 possibilities:

1) the lamp has an intermittant short from the supply(+) leg to the frame of the lamp which is earthed

2) check where the pos supply connects to the lamp lead is exposed enough to short on the frame of the fitting or the metal holder of the globe. they should(usually have a sleeve that slides over the connection.

and also if this is not the problem maybe put a temp fuse on each light to see if you can narrow it down
AnswerID: 362318

Follow Up By: Malleerv - Wednesday, Apr 29, 2009 at 23:30

Wednesday, Apr 29, 2009 at 23:30
Agree with Paul,
My guess is it will be in the light itself and when the vehicle is driven the light vibrates allowing a bare wire to earth to the body of the light internally. Pull your lights apart and check the wires off the globe making sure they have clearance from the back of the lights or if they are bare.

Matt
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FollowupID: 630102

Reply By: Member - Smiley Bill - Wednesday, Apr 29, 2009 at 20:09

Wednesday, Apr 29, 2009 at 20:09
Hi Geoff M,

It would pay to check every inch of the wiring as well, a wire rubbing on something hard would wear the insulation and would cause a short as it moves about.

SB
AnswerID: 362325

Reply By: troopy 2005 - Wednesday, Apr 29, 2009 at 20:14

Wednesday, Apr 29, 2009 at 20:14
process of elimination,connect the light to the battery with a fused wire ,fuse blows problem within the light. If not by pass switch ,change relay.
AnswerID: 362326

Reply By: Member - Stuart P (WA) - Wednesday, Apr 29, 2009 at 22:51

Wednesday, Apr 29, 2009 at 22:51
check wiring to rear of globe , if in any doubt replace globes, i suggest phillips globes , they are so much better than anythig else at the moment .,
AnswerID: 362365

Follow Up By: Member - Stuart P (WA) - Wednesday, Apr 29, 2009 at 22:52

Wednesday, Apr 29, 2009 at 22:52
make sure all connections are insulated
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FollowupID: 630098

Reply By: Member - Mike DID - Thursday, Apr 30, 2009 at 08:04

Thursday, Apr 30, 2009 at 08:04
All QI bulbs draw ten times the normal current for a fraction of a second until the filament heats up and increases in resistance.

A 100 watt globe draws 8 amps when hot, so it has a resistance of 1.5 ohms - so when it's cold it has a resistance around 0.15 ohms - meaning it draws 80 amps initially.
AnswerID: 362396

Reply By: Member - Mike DID - Thursday, Apr 30, 2009 at 08:07

Thursday, Apr 30, 2009 at 08:07
Maybe the fuseholder has lost its tension or corroded and is heating up causing the fuse to blow early.

Check the fuseholder temperature.
AnswerID: 362398

Reply By: Geoff M - Thursday, Apr 30, 2009 at 12:42

Thursday, Apr 30, 2009 at 12:42
Thanks everyone for your comments and information. I'll try these ideas out this weekend and hopefully find the problem.
AnswerID: 362439

Reply By: RobAck - Thursday, Apr 30, 2009 at 20:16

Thursday, Apr 30, 2009 at 20:16
Check the relay in the first instance to see if it has a bridging short. Sounds like it but with electricals it is a case of check everything. Sometimes it is as simple as a lousy earth. I seriously doubt the lights themselves are the problem. It has more to do with the wiring setup. Also check where any wires go through or past metal and see if there is any wear. Hard to spot and again another easy thing to overlook

Regards

RobA
AnswerID: 362492

Reply By: Geoff M - Monday, May 04, 2009 at 07:52

Monday, May 04, 2009 at 07:52
Checked out the wiring over the weekend and found an intermittent short on the light's casing.
Fixed this up, did some more wiring tidy-up and all's good.

Thanks everyone for your comments and suggestions.
AnswerID: 363081

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