Fuses keep blowing

camerart · 19 Aug 2019

Hi,
I've been looking for a fault with my MX5 hazard and indicators.

I've now found that the fuse had gone, even after changing it (10AMP).

With a new fuse the hazard ran for approx 10 clicks, then blew.

I made up a fuse with an external 'chocolate block', allowing me to add a 10AMP fuse wire. Now it is working ok. I used house type fuse wire, which I assume is ok.

I've ordered some more vehicle fuses.

What is going on? Any ideas please.

Cheers, Camerart.

Burnerman · 19 Aug 2019

You’ll really need to measure the actual current draw through the wire before coming to an absolute conclusion......maybe the house fuse wire will allow slightly more current to pass.
I’d make sure the 10A fuse is the one recommended, just in case the original was rated at 15A or whatever.
John

camerart · 19 Aug 2019

Burnerman said:
You’ll really need to measure the actual current draw through the wire before coming to an absolute conclusion......maybe the house fuse wire will allow slightly more current to pass.
I’d make sure the 10A fuse is the one recommended, just in case the original was rated at 15A or whatever.
John

Hi J,
Ok, thanks.
The fuses I used were vehicle red 10Amp, so they must be ok.
It's difficult to measure the current, as being a flasher unit, I don't think they stay on long enough to read.
C.

JohnD · 19 Aug 2019

just to check, is it just the four indicator lamps @21W each that flash (plus 2 side repeaters @5W if you have them)?

That should be around 8A but a bit higher if your circuit voltage is greater than usual.

Not headlamps, fogs or anything? No wiring for a trailer?

camerart · 19 Aug 2019

Hi,
I was told by a mechanic to ON/OFF the hazard switch, lots of times, to clear the points. I did this for 5mins.

With the hazards and indicators working ok. I fitted another 10AMP vehicle fuse, instead of mine, and it seems to have cleared.

It's as if the switch contact were buzzing perhaps and causing too much ON/OFF current.

Let's hope that's cleared.

Thanks, C.

Mottie · 27 Aug 2019

Years and years ago when I was working in a Ford dealership, we had a near new Mk5 Cortina, under warranty, that kept blowing lighting fuses. No one could find the fault and electrics is not my strong point. Anyway, I got to have a go. I was leaving at the end of the week so I wasn’t really bothered. What I did was to get my apprentice to hold the points of a pair of long nosed pliers across the fuse terminals and I looked for smoke! I found it almost immediately- when smoke started coming from the automatic gear lever. When the vehicle was being assembled and the gear lever housing was being screwed down, someone had put a screw right through the wire that went to the small bulb that lit up the gear display. I taped the wire up, fitted a new fuse and job done. Only try this if you are leaving the job anyway and don’t give a ****!

camerart · 27 Aug 2019

Motman said:
Years and years ago when I was working in a Ford dealership, we had a near new Mk5 Cortina, under warranty, that kept blowing lighting fuses. No one could find the fault and electrics is not my strong point. Anyway, I got to have a go. I was leaving at the end of the week so I wasn’t really bothered. What I did was to get my apprentice to hold the points of a pair of long nosed pliers across the fuse terminals and I looked for smoke! I found it almost immediately- when smoke started coming from the automatic gear lever. When the vehicle was being assembled and the gear lever housing was being screwed down, someone had put a screw right through the wire that went to the small bulb that lit up the gear display. I taped the wire up, fitted a new fuse and job done. Only try this if you are leaving the job anyway and don’t give a ****!

Hi M,
Shame it was a **** moment, but following what you say:
I once was searching for a fault in a motor control PCB. At night with the lights out, I looked carefully and could see a tiny glow on one of the chip pins.
From what you said above, I suppose that instead of shorting out the faulty wire, perhaps raising the resistance slowly, while checking with a temperature gun, maybe it would show as a hot spot, without any melting or changing jobs.
C

Fuses keep blowing

camerart

Burnerman

camerart

JohnD

camerart

Mottie

camerart

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