Fuse box getting hot

quattro

quattro

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I went for a run today, quite a long one. (in the car)

After the 160 mile there and 40 miles of the trip back, the fuel pump stopped working and deposited me on the side of the A47 dual carriageway.

After a few minutes of scrabbling around underneath the car and teaching the nearby wildlife a few new words, I discovered that the fuse marked 'ignition control' (21-22)had got so hot that it had melted the surrounding plastic and had dropped down slightly losing its contact.

The heater motor also stopped working.

Pushing the fuse into the lower clip and then holding it against the upper clip got it working, but pushing it into the upper clip didn't work as the plastic had coated both sides of the spring clip and was now insulating it? :shock:

Just holding it there got both the heater motor and the fuel pumping working so after a quick bodge I set of for home.

I have seen this once before when I installed a new wiring loom into a car - but a later model than the loom was designed for.

It does appear that the fuel pump has been wired into the back of the fuse box somewhere - should it need to be wired in by way of a relay, perhaps straight from the battery which is only a couple of feet from the pump?

I have a few small other electrical problems which may or may not be linked.

When you turn on the map light, the radio goes off :?:

The tacho will sometimes read half of what it should do - i.e. it shows 1,000rpm when I know the engine is doing 2,000.

The windscreen wipers run in the off positon, but not in the delay position.

Any ideas ?
 
Hi Quattro I would certainly run the pump through an ignition fired relay.

As for your other bits & bobs it sounds like a combination of faults most of which I suspect are down to somebody making some wrong connections behind the switch panel ie it sounds like the radio is supplied from the map light cicuit but without checking a wiring diagram I'm not committing to this theory.

Quite often the consumer is fed directly by a live wire & then returns to earth via the switch & what I've seen happen & done myself :oops: is you stick a meter on at the switch & find a 12volt supply so you tap into it & your radio works but then when you turn the light switch on the current is used up by the interior lights thus the supply to the radio dissappears.

I made the same error when installing tachographs into some LDV minibuses I found a live & used it & my tachograph worked beautifully but when the colder weather came & the customer turned the heater on the tachograph went off & what I found was the current ran through the motor first & back to earth via the switch (what a f*?!in plonker I felt)

I hope that makes sense
Regards Colin
 
Thanks Colin

I have a wiring diagram for the suffix 'E' car and will be having a good look over the weekend if time allows.

Have you ever seen a fusebox melt though?
 
Oh yes & burned my fingers on the little swine :cry:

The trouble is if you have something which uses a fair bit of current running straight through a fuse box you dont get that sudden overload that pops the fuse instantly you just get a constant slow overload which heats everything up but not quite to the point of blowing the fuse & an electric pump draws a fair bit.

To try & simplify what I mean a lot of glass fuses have eg. 2 amps continuous 5 amps blow so if you are using say 4 amps through it it wont go instantly as it would take 5amps to pop it but you are using it beyond it's reccommended capacity therefore it gets hot & that's why the fusebox melts

I do believe I've made that sound as clear as mud :? but at least I know what I mean

Regards Col
 
Been having a play with the fuse box and have discovered that the the main feed into fuse 21.22 is into the left hand blade only.

The right hand blade of 21.22 feeds the left hand blade of fuse 23.24 which in turn feeds fuse 3.4.

So all of the power going through fuse 21.22, fuse 23.24, and fuse 3.4 is going through the left hand blade of fuse 21.22 and then through the metal cap of the fuse itself.

So the little cap is taking all of the power to the heater motor, Wiper switch and wipers, radio, Heated rear screen, and anything else that has been added to it at a later date, including in this case, the electric puel pump and possibly the kenlowe fan as well. And it got hot as you can see.

I am considering taking the large feed wire from the ignition switch (currently feeding the LH blade of 21.22), into a junction box and feeding fuses 21.22, 23.24, and 3.4 separately from this. This should help with the overheating.

Also taking a feed from the junction box to a relay which could run the fuel pump from a fused battery feed. It's very close by.

I have a new fuse box but don't want to just change it as the problem would almost certainly occur again.

Any thoughts anyone?
 

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It looks as though that fuse could be the wrong length and that can cause the problems you are having. Most places only sell metric (for the want of a better phrase) fuses now which are shorter than the old style imperial ones which were 1 1/4" long IIRC.

Unfortunately as the fuse box has melted you've got a bigger problem to fix now.
 
harveyp6 said:
It looks as though that fuse could be the wrong length and that can cause the problems you are having. Most places only sell metric (for the want of a better phrase) fuses now which are shorter than the old style imperial ones which were 1 1/4" long IIRC.

Unfortunately as the fuse box has melted you've got a bigger problem to fix now.
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Thanks Harvey. The fuse is not as short as it looks as I have moved it down a little when messing around with it.

I don't drive around with it there.

I will be checking the length of all of the fuses when I put the new box in though.
 
Again without a wiring diagram in front of me it's difficult to be sure but that is quite normal for there to be a "master" fuse feeding "slave" fuses elsewhere in the box but your problem is the extra equipment is drawing a bit too much current but like I said earlier not quite enough to blow the fuse but if you make sure the fuel pump & electric fan are wired through relays I think this will cure your problem as it doesn't take a lot of current to fire a relay & if you jump your main supply to the fan & fuel pump from the unfused side of the fuse box through the relays (add an inline fuse if you like) then Hey Morrisons! no more hot fuse boxes.
TRUST ME I'M A DOCTOR

Regards Col
 
Cheers Col.

I do understand the principals involved, but am wondering if feeding the fuse for the heated rear window directly, and not through the tops of two other fuses might help the situation a little.

I have got some relays on route and will be fitting them as soon as time and weather allows.

Are you really a Doctor? 8)

Richard.
 
quattro said:
Are you really a Doctor? 8)
Click to expand...


Errrrrr! No :roll:

quattro said:
I do understand the principals involved, but am wondering if feeding the fuse for the heated rear window directly, and not through the tops of two other fuses might help the situation
Click to expand...

It wouldn't do any harm but really if that's the way they were from new I dont think you should have any bother anyway & when you think about it the current is passing through the fuse holders aswelll so it shouldn't be a problem.

Regards Dr. Colin
 
2Diesels said:
Richard did you ever manage to sort the other problems out with the wipers, radio & rev counter?

Regards Col
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No - I am going to pull the dash and the switch block out when I change the fuse box.

I am goign to check all of the new stuff, and the map light/radio problem, wipers etc when I do that. I don't want something amiss with a radio pick up melting the new fuse box.

Unfortunately every time I get the chance to do anything, it rains and I don't have the luxury of a garage yet. :evil:
 
I posted this under "No Lights" on 7/11:

There has been quite a lot of discussion on fuses and fuse boxes on here over the years. S1 style with the small fuse box in the engine bay is immune (carries over into early apparently S2 cars) - all these comments apply to the S2 fuse box behind the passenger side shin bin. To summarise there are two particular problems. First is that there is a metric size fuse available which will fit into the fuse holders - BUT it isn't quite long enough and will cause overheating - get the correct imperial size fuses which are still available. The second problem is much more serious and can cause major catastrophe. This fuse box was used in the P5 without any known incident, so it appears the problem is a production fault - perhaps the looms were assembled by a different supplier. The fuse box when used in the P6 is prone to melting / catching fire. This originates from the crimping of the wires into the terminations of the box being inadequate. These then overheat. It is possible to go through an intact box and nip them up to improve the mechanical connection, but once heating has started the box is toast as it deforms very easily and, if it gets to that stage, will burn enthusiastically at a very low temperature. Many people, myself amongst them have replaced the complete box with a modern equivalent.

The information on the electrical path to fuse 3.4 is interesting and relevant as well:

So all of the power going through fuse 21.22, fuse 23.24, and fuse 3.4 is going through the left hand blade of fuse 21.22 and then through the metal cap of the fuse itself.


Without going outside to look, is it not possible just to piggy back the links onto the same blade as the supply?

Regards

Chris
 
Thanks Chris, yes I read your post on 'no lights.'

The main feed wire is too big to enable others to go into the same spade. :(

The pic below shows some of the wires. The far right purple/brown is supposed to be the radio, then the next purple/light brown goes to fuse 3.4, then the large purple/brown is the main feed wire into 21.22.

One thing I noticed, is that the radio feed comes (or is supposed to come) from the top of fuse 23.24, which is fed from 21.22 which in turn, is igniton controlled. So why is the radio operable without the igniton on?

Curiouser and curiouser :?:

Luckily the car is not my daily driver so I have plenty of time to sort it properly.
 

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DaveHerns said:
" Real " wires , not like the tiny guage stuff used on modern cars !
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Yep LOL

I am getting a spare feed wire for that fuse,

- and using it as a tow rope. :shock:

Had a quick look in between showers and the radio, which I was told when buying the car was the original fitted by Rover, is wired into the live side of the map reading light. The wiring for this light goes, from the bottom of fuse 1.2 to the cigar lighter, to a spliced in wire for the radio, to the map reading light and then onto the switch.

Will be sorting that out over the weekend.
 
quattro said:
Had a quick look in between showers and the radio, which I was told when buying the car was the original fitted by Rover, is wired into the live side of the map reading light.
Click to expand...

Hate to blow my own trumpet but TOLD YOU SO :LOL:

Sorry nobody likes a gloater :roll:
Shame Colin Shame

Regards Col
 
In my fuse box (1974 P6B) fuse 3-4 for the heated rear window. Funny thing is, I don't have a heated rear window nor is their a switch fitted to run it. :?

Ron.
 
SydneyRoverP6B said:
In my fuse box (1974 P6B) fuse 3-4 for the heated rear window. Funny thing is, I don't have a heated rear window nor is their a switch fitted to run it. :?

Ron.
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Funnily enough, the fuse 3.4 in mine is also for a heated rear window, but the writing on the fuse box cover states that it is for hazard warning?
 
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