Possible option for those "short" fuses

[Dr.Jeff]

On X's with the ceramic "bullet" ("Euro style") fuses, there are two short ones for the headlight pods:

They have not been available for a long time so getting replacements is difficult at best. There have been a few ideas how to substitute, modify, or otherwise get around them. But I may have thought of yet another option.

The brass tabs that hold the fuses in place are a "push" fit into the plastic fuse panel (see pic below). There is a small tang on the rear of the metal tab to hold it in place, similar to the little tang that holds electrical terminals in the plastic connector housings (orange arrow). By moving the tang inward the brass tab can be removed from the plastic holder. Then a brass tab for a regular size fuse can replace it (similar to the green box), by pushing it into the same slot. Now it uses normal sized fuses:

Note that the ones in the picture are the lower tabs, not the one you need to replace. But they mount the same and look very similar.
Naturally you will need to get a couple of the tabs for regular sized fuses. But that shouldn't be difficult to find. A old fuse panel has enough of them to convert a dozen short fuse holders.

The lower example in that picture is the common "bussed" power supply side of most fuses in the X's panel. They can be separated by cutting out the middle piece (blue arrow). That is how the two single tabs (upper portion of the pic) were made.

 

[iamrikdavis]

Shared knowledge, A+

 

[SuperTopo]

what is the reason that Fiat used these short fuses in the first place?

 

[lookforjoe]

A friend of mine has a supply of the short fuses....

 

[Dr.Jeff]

what is the reason that Fiat used these short fuses in the first place?

Because "Fiat"?

 

[johnph]

what is the reason that Fiat used these short fuses in the first place?

I think this kind of fuse was used by all European cars from VW to Mercedes Benz including Fiat in the 50s, 60s, and 70s.

 

[SuperTopo]

I think this kind of fuse was used by all European cars from VW to Mercedes Benz including Fiat in the 50s, 60s, and 70s.

I know that is true for these bullet fuses. I’m specifically asking about the two short ones. Why are they short? there’s something different about them for a reason.

 

[johnph]

I know that is true for these bullet fuses. I’m specifically asking about the two short ones. Why are they short? there’s something different about them for a reason.

If this was Formula 1, it is to save weight.

 

[EricH]

Now it uses normal sized fuses:

Are the normal-length fuses available with the right rating (which is, IIRC, 5 amps)?

 

[EricH]

Are the normal-length fuses available with the right rating (which is, IIRC, 5 amps)?

And to answer my own question.... https://napaonline.com/en/p/BK_7821102

 

[jimmyx]

And to answer my own question.... https://napaonline.com/en/p/BK_7821102

Fuse M & N on the early fuse block should be 3 amp. Not finding a source for them in a longer configuration? Might be available somewhere, but I would still rather invest the $10 and 30 minutes to just fit the Lada block and be done with it.

 

[Dr.Jeff]

Are the normal-length fuses available with the right rating (which is, IIRC, 5 amps)?

I just looked it up, those short ones are 3 amps in the X. Honestly I'd have to look to see if 3 amp is common. But I know you can get 2.5 and 5 amp ones (as you found). Either of which would be fine in my opinion.

I know that is true for these bullet fuses. I’m specifically asking about the two short ones. Why are they short? there’s something different about them for a reason.

I was being facetious about the "because Fiat" comment. The short format of ceramic fuses is not unique to Fiat. Back in the 60's I had a couple of vehicles that used them. However they were all the short format in those applications, not a mix of short and long like the X has. And that is the part I was referring to as a typical Fiat thing to do.

The short format was just another size option. Much like the "glass tube" fuses we are familiar with also come in different lengths/diameters (AGA, AGX, AWG, SFE-6, SFE-14, etc). Although the short ceramic ones weren't all that common, they were used in certain applications. I believe they were initially intended for things like electronic devices (radios, etc) where there was very limited space. But some smaller vehicles (e.g. scooters) also used them. Back in those days vehicles only had a few circuits, some of which weren't fused. So a fuse panel only had maybe 2 or 4 fuses. With the smaller format of fuses the whole panel could be made very compact to fit in tight places.

I know those short ceramic fuses were available in a wide range of capacities. From roughly 1 amp up to about 25 amp, as I recall. So it wasn't to do with their ratings, just the footprint. Therefore I have no idea why Fiat used two short ones for the headlight door circuits. Even more odd is why they fused those two relays' trigger circuits but not many others? In fact there is a rather long list of things that aren't fused at all. Some of which (like the ignition system) that seem to be rather large draws, pretty sensitive components, and very critical functions.

 

[Dr.Jeff]

Fuse M & N on the early fuse block should be 3 amp. Not finding a source for them in a longer configuration? Might be available somewhere, but I would still rather invest the $10 and 30 minutes to just fit the Lada block and be done with it.

The GBC-5 (5 amp rating) ceramic fuses are extremely common. Other sizes are made but not as easy to find. As I mentioned those two fuses only protect the "trigger" side (terminals 85 and 86) of two relays (one on each fuse). Frankly that isn't a critical item and they actually draw less than 1 amp. So this whole short fuse thing is really dumb in my opinion. But a 5 amp fuse would certainly be sufficiently safe for this.

 

[dwoof]

I made some 5 amp shorties from some longer fuses but they look odd. I can't find 3 amp fuses. I'll probably swap for the Lada block eventually, right now I'm in the 'just get things working' phase.

 

[Dr.Jeff]

Fuse M & N on the early fuse block should be 3 amp. Not finding a source for them in a longer configuration? Might be available somewhere, but I would still rather invest the $10 and 30 minutes to just fit the Lada block and be done with it.

I made some 5 amp shorties from some longer fuses but they look odd. I can't find 3 amp fuses. I'll probably swap for the Lada block eventually, right now I'm in the 'just get things working' phase.

Unfortunately the Lada fuse panel will not work well for all X's with ceramic fuses. On the early 1300 cars with the panel located on the left (drivers) side, it works fine. But on the 1500's with that type of fuse and the panel located on the right (passengers) side the Lada item does not have enough fuse positions available. There are 19 fuses on those X's (including the inline ones, 16 on the panel). It has been suggested you might be able to buy two of the Lada panels, cut them and splice the two to make one. But in my opinion that doesn't sound like a ideal solution. There is nothing wrong with the ceramic style of fuses. Yes the tabs should be cleaned once or twice in there life, but I also find that to be true with other styles of fuses. Personally I've owned numerous cars with ceramic fuses and have never experienced a single problem due to the fuse or panel. A personal choice for sure.

 

[dllubin]

Unfortunately the Lada fuse panel will not work well for all X's with ceramic fuses. On the early 1300 cars with the panel located on the left (drivers) side, it works fine. But on the 1500's with that type of fuse and the panel located on the right (passengers) side the Lada item does not have enough fuse positions available. There are 19 fuses on those X's (including the inline ones, 16 on the panel). It has been suggested you might be able to buy two of the Lada panels, cut them and splice the two to make one. But in my opinion that doesn't sound like a ideal solution. There is nothing wrong with the ceramic style of fuses. Yes the tabs should be cleaned once or twice in there life, but I also find that to be true with other styles of fuses. Personally I've owned numerous cars with ceramic fuses and have never experienced a single problem due to the fuse or panel. A personal choice for sure.

The ceramic fuses actually have 2 less metal to metal interfaces than the glass fuses. The glass commonly used back then are really no better than the ceramic ones. The glass fuses are not sealed in any way. The fuse material strip is inserted in the glass tube and the ends are folded over the outside of the tube with a small amount of material on the exterior. Then, they jam the end caps on which provides continuity to the fuse material. I have had this style of fuse go near open circuit when the fuse material oxidizes and no longer conducts well to the end caps.

 

[Dr.Jeff]

The ceramic fuses actually have 2 less metal to metal interfaces than the glass fuses. The glass commonly used back then are really no better than the ceramic ones. The glass fuses are not sealed in any way. The fuse material strip is inserted in the glass tube and the ends are folded over the outside of the tube with a small amount of material on the exterior. Then, they jam the end caps on which provides continuity to the fuse material. I have had this style of fuse go near open circuit when the fuse material oxidizes and no longer conducts well to the end caps.

I have some glass tube style fuses in the ceramic fuse format. In other words they are the "GBC" footprint, and fit the European ceramic fuse panels, but are constructed with a glass tube and metal end caps like the American style fuses. The end caps are cone shaped to fit the tabs on a ceramic style panel. Not too long ago I saw some of them still offered by one of the big fuse makers (Littelfuse I think), but no longer. And as you say, they are no better.

 

[dllubin]

I've actually got a few Littlefuse metal boxes with the glass fuses having cone shaped ends for ceramic fuse compatibility. I may still have some of the short ones in that style.

 

[Dr.Jeff]

This whole topic of fuses came up as I sort through the entire electrical system on one of my current X project builds. I started the job with the intent of just checking and repairing any needed areas, cleaning terminals, and adding some extra relays to save the switches from their load. But the more I got into it things just kept getting worse and worse. Not that there were any specific issues, in fact everything was working perfectly before I began. And there were NO prior-owner bodge-jobs anywhere, everything was original. However I discovered a LOT of what I consider to be design faults in how the electrical system was laid out and built. As I've mentioned there are several unprotected components, many more that are wired very precariously, a ton of excess wire due to the inefficient routing of things, loads of questionable connectors/terminals, plenty of undersized wires, careless installation, and various other issues. So I decided to completely revamp the whole system from end to end. This also enables me to add a load of custom features into the build and include them in the original architecture.

One of my goals was to incorporate all of the upgrades - like added relays, circuits, and fuses - into the existing fuse box, rather than add on extra panels. That part has been achieved, but with considerable re-engineering. One limitation with the X's fuse panel is there are not many places to attach wires. For the most part each fuse allows two input and two output connections. That would be fine if there were a lot more fuses, but there's only a handful (hince the Lada fuse panel comments earlier). So I split some of the bussed circuits (as shown in my original post), reconfigured the power inputs to each circuit, reorganized the outputs from each circuit, and added several of the factory style relay holders onto the existing ones (they clip onto one another). By significantly reducing the load to many of the circuits (with the added relays) I've been able to combine two or three wires onto a common fuse. I'm not talking about combining circuits, but things like the power and ground leads to the relays' trigger terminals (85, 86) are now daisy chained (where possible) to reduce the number of contacts needed on the fuse panel. With all LED bulbs installed I could combine some lighting circuits as well. I've also eliminated a couple of circuits altogether; for example things like the seat belt buzzer (which was already disconnected), the smog controls (replaced with a aftermarket ECU), and the old AC circuit (replaced with all modern technology). So basically I've pretty much made a completely new wire harness. But I utilized as much of the original wires as possible to try and retain some of the color coding.

I had to wait for some new connector terminals to arrive, and the grueling summer heat here has prevented any outside work for the last couple of months, but I'm still working on it. Just making sense of a lot of the original design was a huge task in itself. This happens to be a US model, Calif smog spec, '79 with all of its unique features. So many areas are not common with other X's. All in all it has turned into a much larger task than I had planned.

 

[dllubin]

I think one of the reasons the wiring harness got so weird on the X was that regulatory requirements were layered on the car as time went on. Also, more stuff was added - AC, stereo, catalytic converter, etc.

The electrical system on my 74 is pretty stark and the wiring is sized about right for a 32 Amp system. Perhaps Fiat forgot what the system was originally designed for when they started to apply the Band-Aids.