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Should A 30 A Fuse Blow Almost Immediately After Fitting

electrical

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#1 Vinay-RS

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Posted 10 December 2023 - 08:57 AM

Hi all, 

Possibly a very dumb question. I have checked the Haynes manual and past posts on TMF and confirmed that the indicator fuse should be a 35 A fuse. I haven't had any luck at the local motor spares shops near me when finding one, so popped in a 30 A fuse to see if it would do the job but within 5 minutes of driving it blows. Just confirming that this is simply because the fuse rating is insufficient or if it could be that there is a short somewhere in the loom. 

 

I did recently remove the alarm system as the folks who fitted it had spliced and sliced it into every wire under the steering column and it was failing and causing havoc with all the electrics. I checked that the flasher unit was working by plugging it into the hazard flasher spot and it seems to be working and I repaired the connectors that were spliced by the alarm installers by twisting, soldering and sealing with some electrical tape as I didn't have any heat shrink on hand. 

 

Cheers, 

Vinay



#2 MiniMadRacer

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Posted 10 December 2023 - 09:31 AM

Doesnt sound right to me. The 35 amp fuse covers a range of ancillaries, and is rated assuming you have them all on at once. What have you got on i.e switched on, when you are driving



#3 absx2

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Posted 10 December 2023 - 09:34 AM

Sounds like you have a wire or two touching to each other or earth.



#4 Steam

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Posted 10 December 2023 - 09:34 AM

In short, No the fuse should not blow. The original fuse should be a 17A with a 35A short term hold. These were/are the fuse that most all cars had back in the day.
By process 9f eliminatio you will track the fault. If you fit a fuse and just let it sit does it blow or only when driving or does it blow with the ignition on etc.

#5 Vinay-RS

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Posted 10 December 2023 - 09:36 AM

Just brakes and indicators. Don't even have a radio fitted to the car.

Are there ways to test the system to find the source of the short? I do have access to a multimeter but I'm a little clueless on fault finding.

#6 Steam

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Posted 10 December 2023 - 09:42 AM

Put a nail in and follow the smoke. ;-)
Seriously though no only by a process of logical illimination

#7 Vinay-RS

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Posted 10 December 2023 - 09:55 AM

So a quick check. Plugged in the 30A fuse with the ignition in and it doesn't blow. Disconnected the brake light switch and put the ignition in and it doesn't blow. Switch on the indicator switch both left and right and it doesn't blow. I guess the last check is to connect the brake light switch and see if it blows the fuse.

#8 Quinlan minor

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Posted 10 December 2023 - 10:30 AM

.

Attached Files



#9 Vinay-RS

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Posted 10 December 2023 - 10:36 AM

Haha! Saw that the other day and had a good chuckle.

So I reconnected the brake light switch and it didn't blow the fuse. Turned on the ignition, tested the brake switch and the indicators at the same time and it didn't blow the fuse.

So the conclusion is it must be the reverse light switch that is the problem. I had disconnected this first.

#10 Quinlan minor

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Posted 10 December 2023 - 10:47 AM

So the conclusion is it must be the reverse light switch that is the problem. I had disconnected this first.

I've seen the reverse light cable burned on the exhaust pipe a couple of times. That's a good place to start your search.



#11 bpirie1000

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Posted 10 December 2023 - 01:11 PM

Make sure all wires under the ignigtion are tapped up before anything else happens to the car..

Also lookmat the hazard warning switch as they share the same wiring loom.

#12 nicklouse

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Posted 10 December 2023 - 01:42 PM

Mmm have you changed the 2 clock to the 3 clock set up?

 

not all the connectors are used on the PCB.

 

This fuse that is blowing. It is ignition position 2 live only?



#13 Vinay-RS

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Posted 10 December 2023 - 02:32 PM

Mmm have you changed the 2 clock to the 3 clock set up?

 

not all the connectors are used on the PCB.

 

This fuse that is blowing. It is ignition position 2 live only?

not yet. It was on the to-do list for some years now. 

 

Yes, it is the ignition live fuse. 



#14 Vinay-RS

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Posted 10 December 2023 - 02:34 PM

Make sure all wires under the ignigtion are tapped up before anything else happens to the car..

Also lookmat the hazard warning switch as they share the same wiring loom.

Everything is taped up under there. It's not neat but I think the ignition circuit is happy. 



#15 Vinay-RS

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Posted 10 December 2023 - 02:35 PM

I did take the car on a quick drive around the block (10-15 min) and it seems fine now. I think the reverse light switch is the problem. I'll pick up a new one in the week (hopefully the spares shops still keep them here) and swap that out and see if that fixes the issue. 


Edited by Vinay-RS, 10 December 2023 - 02:35 PM.






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