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I've been having a few problems that might be electrical in my car.

Seeing as mechanics always want to replace parts first, I'm having to diagnose this problem myself.

It seems like replacing all the fuses would be cheap and preventative, and more effective than a voltmeter with my limited knowledge of electrical.

I drive a 2004 1.7L Honda Civic Si, the US version.

Could this cause problems for my car? Would it help with the diagnosis?

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    "mechanics always want to replace parts first" - I think you need a better mechanic. Efficient diagnostics are what separates a good mechanic from a shadetree amateur. – PeteCon May 12 '16 at 15:09
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    @Pete I think part of it is pink tax, because they squirm when I ask more questions. – Betsy Dupuis May 12 '16 at 15:12
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    Depends on the part. For a fuse, 200% isn't unknown. For an alternator, it's a little excessive. But this isn't on topic. I think a great way for you to proceed is to put a question up about what's happening on your car, and the experts here should be able to point you in the right direction. It's very unlikely that anything going wrong on your car hasn't been seen before. – PeteCon May 12 '16 at 15:26
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    This idea is rather pointless. If the fuse has blown, the replacement will (or should) also blow instantly unless you fix the reason why it blew. If your fuses are unreliable because the connectors are corroded or dirty, you need to figure out why they got in that condition and fix the root cause of the problem. I don't know the "official" expected life of a fuse carrying the current it was designed for, but I would guess a number like 50 or 100 years. – alephzero May 12 '16 at 16:48
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    i feel like replacing fuses is the same kind of thinking you say the mechanic is following. while replacing the fuses might show corrosion in the terminals, unless there's voltage drop on a circuit or it's obviously blown your replacing them for no practical reason. In the long run your better off buying a multimeter and learning how to do basic circuit testing. and like @Pete said create a new question and someone will be able to help you diagnose the problem. – Ben May 12 '16 at 17:20
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Fuses do not need to be replaced unless they have blown, so it's not a regular maintenance thing.

In terms of checking them, depending on your vehicle, many only require a visual check to see if the metal is present or missing.

If you do have fuses where their status is not obvious, a good multimeter is only a few dollars (probably cheaper than replacing all the fuses, anyway) - and you will find it useful round the house, and for other small jobs once you have one. Make sure you get a reputable brand.

Replacing all the fuses should not cause any problems with your car, unless you get the fuses wrong, or don't fully seat them etc. On balance, much better off just testing them all with a meter.

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    Most fuses have two exposed bits of metal on the top so you can even check them without removing them. – JPhi1618 May 12 '16 at 15:13
  • Old coded radios could making pulling fuses a bad idea unless you knew the code - and we know nothing about the car. – Chris H May 13 '16 at 8:29
  • I almost up-voted this answer... A multimeter that costs only a few dollars is a hand-granade when used near mains, which is interpretation that could be reached from the around the house part. While dirt-cheap multimeters do have their own uses, and continuity test on fuses is one of them, it's dangerous to recommend them as a general-purpose unit for beginners!!! – AndrejaKo May 13 '16 at 13:40
  • Totally disagree AndrejaKo - even my 10 year old is perfectly safe using one. They are simple, and even the £7.50 one my youngest has is well protected, and very safe. Sure, I wouldn't let her at any of my high voltage supplies, but mains power is relatively safe. Even for beginners. – Rory Alsop May 13 '16 at 13:42
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    Thanks! Here in the UK, Maplin has an excellent range, all certified to British Standards. I guess some countries may not have the same quality control mandated by law. – Rory Alsop May 13 '16 at 19:01
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As a general maintenance practice or a troubleshooting method without having a particular reasoned approach, no. If it's troubleshooting, testing the fuses on their exposed blade tips is equivalent.

That said, replacing the fuses shouldn't create any risks so long as you're replacing them with the appropriate values.

It should be pointed out that fuses can exhibit cumulative degradation due to short-term overcurrents which were insufficient to open the fuse. This can reduce the fusing current, but until the fuse actually opens, it's not going to be producing any problem symptoms itself. Even if this were a concern, replacing the fuse wouldn't fix the source of underlying periodic overcurrents.

In other contexts, (e.g. large mains cartridge fuses), the fuse body is filled with an arc suppression filler such as calcium carbonate. In damp environments, this can absorb moisture and cause corrosion of the fuse elements. In these cases, maintenance fuse replacement might be a valid stop-gap approach to avoid replacement of the protection equipment. There aren't any filled fuses in typical automotive applications.

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Replace them all? No. As others have mentioned, they're either working or they're not. Test them with a multimeter or fuse tester. Be sure to look for "fusible links" in the wiring on a newer car, not all fuses are in the fuse box anymore for some unfathomable reason...

Take them all out, one at a time, and clean them? I've had that help on some vehicles. It's especially worth the effort if your problems are intermittent. Between vibration and corrosion it's quite possible for the connection between fuse and socket to become unreliable. Pull it out, clean off the corrosion, coat the contacts with anti-oxidation grease like is commonly used in electrical panels, and put it back. Should last quite nicely after that.

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    Pencil eraser cleans electrical contacts well in most cases. – user15009 May 13 '16 at 1:33
  • Yep. And while you're at it, do the relays too, they're another common source of intermittent electrical problems. – Perkins May 19 '16 at 19:34

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