Fuse box - Replacing

J

John Larkin

Member
I need to replace the fuse block in my 1974 3500. The repair and operations manual just says to disconnect the connections at the fuse block, but I cannot see how to do this. They do not appear to pull off, although I suspect that they are supposed to, but I am afraid of causing damage if I try too hard. Has anybody changed a fuse block? Any help much appreciated.
 
I haven't, but both my S2's fuseboxes need replacing. As far as I've seen the wires are soldered directly to the fuse clamps so you can't pull them off. You'd have to pull each 'clamp half' out one by one & insert them in a new plastic box with it's own clamps removed. A bitch of a job given the length of the wires & the position of the fusebox.
Easier to fit in-line fuses (as mentioned in another thread) to the affected parts of the box though not as tidy.
 
I see what you mean. I have a problem with power supply to the fuse for my heater fan motor. Current is supplied to the adjacent fuse head (wiper motor) and is delivered to the heater motor fuse head by a copper bridge which has developed a crack. There is a high resistance through the bridge piece (about 80 Ohms) and it gets very hot; it also delivers current intermittently. I think that a new power take-off and an in-line fuse make more sense than changing the whole fuse block.

Thanks,

John.
 
It is the rivet that causes high resistance on the bridge piece, I have successfully tightened them by using a flat nosed punch.
 
I had done this but it is awkward but only because you haven't cot much slack on the loom.

The connections will slip out easy enough. The push in from the back and lock in with little barbs, like you get on fish hooks. If you push in a watch makers screw driver or something similar in at the fuse side the connector will slip out.

When I did it I replaced most of the connectors and soldiered them instead of crimping them. was definatley worthwhile as with the standard head lights I melted the box.

Colin
 
An old subject, I know but I have changed my fusebox on my 1973 V8 Auto at the weekend following a serious but progressive meltdown of the box at the position of the inner main beam fuse.

Not quite sure what has caused this, but I pushed the connectors out using a thin bladed screwdriver to flatten the molding latch on each whilst carefully labelled each wire using a 1-48 numbering system. I needed to replace 2 of the connectors as it was not possible to extract them due to the plastic melting around them and 'glueing' them in place. This was achieved by taking some of the spare uncrimped connectors from the melted fusebox, cutting the 2 wires off and crimping them using tool MP71 available for around £8.55 + VAT from Vehicle Wiring Products. This is an excellent tool which with practice gives high quality crimps.

Before I installed a good (non-melted) 2nd hand fusebox, I did the following:

(1) Highly polished all off the connector faces (where they meet the fuse) with fine wet and dry and finished with a sparing application of Autosol metal polish. This was carried out on both the static connectors in the new fusebox and also the ones fixed to the car.

(2) Lifted the flattened barbs on the connectors very gently with the thin bladed screwdriver to enable them to engage with the new fusebox.

(3) Invested in a set of brand new and shiny fuses.

(4) Once all the connectors were inserted in the new fusebox but before fitting the new fuses, with a pair of long nosed pliers I pinched the connector faces together to ensure they gripped the fuse nice and tightly (a loose fuse creates a high resistance, heat and a melted fusebox).

I have not tried it out yet, but will power up with the car stationary (with main beams and fan on) and monitor the fuseboard closely to see if it gets hot......

If it starts to melt again after all this work I will either bypass main beam and use an in-line fuse or replace the whole fusebox with a more modern type (Vehicle Wiring Products sell a 12 way box with Lucar Connections on the Input/Output).

Watch this space....

??? ??? ???
 
ps. After fitting the new fusebox, in an act of 'testing/punishment' towards the old melted box I undertook a 'test' on it to determine just how susceptible the fusebox was to melting. I gently held it momentarily over the ring of the gas cooker...

Imagine my surprise when after just a short exposure to flame, the plastic 'caught' and a very small (pea sized), gentle, but steady bright and pure blue flame (like a bunsen flame) started licking its way aound the box in the corner. Not wishing to set my house alight, I took it outside to monitor progress. The pea sized flame grew slowly, but powerfully and progressively across the entire fusebox in a pure blue flame until it was completely consumed after around 5-10 mins. The flames went out and what was left just a small puddle of black waxy and crispy waste.

What are these fuseboxs made from???!!!!
 
Yep! The S2 fusebox is not a success is it! I replaced mine with a proprietory fuse box as described by rp61973 and feel much more confident now. Those lucky enough to have S1's or early S2's with the S1 fusebox need only worry about lack of fusing and fitting a few extra in line fuses as appropriate!

Chris
 
Hi Chris,

Many thanks - it is good to hear from someone who has had similar experiences with this unit.

The more I think about it the more tempted I am to junk the standard fusebox and go for a modern unit with the bladefuses. For now I will monitor the replacement standard unit I have - any sniff of melting on the main beam circuits and it will be straight out of the car and held over the gas cooker ring for punishment/entertainment!
 
Personally, I always see it as a miracle when the electrics work, considering all those bullet connectors and the inevitability of corrosion.
I have headed for inspection with everything working, only to arrive with something out. Then it is wiggle and prod time.

Dick West
 
Well hopefully no more toasting fusebox. I tested the refitted fusebox at the weekend. I ensured the contacts were pinched tightly together with the aid of some long nosed pliers and also ensured the contact faces were bright and shiny before fitting the new fuses. I had the engine running and had mains beams on and the heater at full pelt. After around 1/2 and hour the fuses were just tepid to the touch, so fingers crossed.......

I will periodically take the cover off and check for future problems.
 
You might also want to get some "Switch Cleaner" or "Contact Treatment Oil" , comonly refered to as "Servisol" Link To Maplin Website This stuff helps keep the contacts working and prevents arcing which is usually the main cause of meltdown. Works on bullet connectors, multiplugs etc.. as well, I always have a can in my tool box.
 
Hi Richard and many thanks. I will certainly invest in a can of this, remove each of the fuses again and give the contacts a gentle 'squirt'. What I will also sort out is the fuses. I did not realise until this morning that you can buy both 30mm long and 31.8mm long glass fuses. I sent off to Vehicle Wiring Products for what I thought were the correct fuses for the box, only to find that they are a little too short. Needless to say, I will change these to the 31.8mm (old imperial size) fuses before I connect the battery up again (which is currently having a charge). Funnily enough, I found that Halfords supply the correct length fuse and even supply the 8 Amp variety! I will check to see if they do the 5, 15 and 25 Amp fuses also.
 
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