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#1 A fuse blows on start up

Posted: Wed Apr 24, 2019 7:33 am
by Philthecat
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The attached image is from a LH drive spec car and mine is a UK spec Series 1, so the feature I want to know the function and name of is on the right instead of the left.

Q: What, please, is the block attached to the top inside the instrument panel?

Connected to it, it has 2 plain green wires at upper 2 connections and a green with a darker tracer (perhaps darker green or blue) and a black wire on lower connections. The block is marked with an earth symbol.

My fuses are not allocated normally which has complicated my amateur investigations somewhat. The fuse that is blowing on start up is in number 5 position which is normally used for side, tail, panel and number plate lights, but it seems that mine instead has fuel pump, choke and gauges, but I'm not certain if that is the full complement. Side lights, tail and number plate light are connected elsewhere on other fuse positions. I think the instrument panel lights are also connected to this fuse position.

By disconnecting the 4 wires mentioned above, the car does not now blow the offending fuse at start up and now runs OK.

I noticed yesterday when investigating the blowing fuse, that the earthed block I'm asking about heated up hot to the touch. Car would not operate fuel pump so would not start. I switched off the ignition before the fuse blew. I then disconnected all 4 of the wires mentioned above from the block. Fuel pump operated and car started with choke no problem. Car is well sorted on starting and runs well. Being a warm day, I took off choke and let car warm up. All seems good, but I stayed on the drive because I need to know that I'm not going to conk out a couple of miles up the road.

I have a proper published Jaguar Service Manual covering all 6 cylinder models but this basic information is not to be found. The glorious black and white circuit diagrams are not great!

I believe the block to be something to do with instrument panel lights or the instruments themselves, but I'm guessing. It may be a red herring, but full beam not working, but dim beam OK.

Thank you in anticipation,
Philthecat

#2 Re: A fuse blows on start up

Posted: Wed Apr 24, 2019 7:45 am
by abowie
It is a voltage regulator that provides 10V DC to some of your instruments.

The plain green wire is fused switched 12V into the regulator. The Green/black wires are 10v out to the instruments.

#3 Re: A fuse blows on start up

Posted: Wed Apr 24, 2019 7:46 am
by mgcjag
Voltage regulator...Steve

#4 Re: A fuse blows on start up

Posted: Wed Apr 24, 2019 7:47 am
by abowie
It is a voltage regulator that provides 10V DC to some of your instruments.

The plain green wire is fused switched 12V into the regulator. The Green/black wires are 10v out to the instruments.
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#5 Re: A fuse blows on start up

Posted: Wed Apr 24, 2019 5:44 pm
by Polse7317
may be that can help you ?
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#6 Re: A fuse blows on start up

Posted: Thu Apr 25, 2019 12:08 pm
by AshM
Phil

I have the facility to print large (A3 up to A0) colour copies of the wiring diagrams from the knowledge base.

Quite a few forum members have taken me up on this and always seem pleased with them.

It’s my ‘service to say thank you’ back to the forum. 😀

PM me if you would like one with your address and I will get some printed off.

Cheers
Ash