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Extended use of wrong amp fuse--potential problems?

Howdy! I have a 1990 Camry that I bought 1.5 years ago. She’s always had a lot of minor electrical problems in all systems (radio, turn signal, interior & exterior lights, etc). Today I finally got around to checking every single fuse by hand. I’ve never touched fuses before, and have very little experience fixing car trouble. I did replace my own blower motor, so I can at least do that level of repair.

Anyway, one of my fuses was fried inside. Turned out the fuse was a 25 amp where it was supposed to be 15 amp. It controls tail lights. It’s apparently been that way for at least 1.5 years, or more.

Ever since I got it it’s been making a shrieking sound when the left indicator was used, unless the indicator was held in a very small sweet spot. The problem isn’t fixed since I fixed the fuse, but that sweet spot is a lot bigger now, and a lot less of a problem to find.

The previous owner said it started making that sound the day I bought it, when he was driving it back from being smogged (aka inspected, to those not from California). I’m wondering if they replaced a fuse wrong when smogging it, and what the potential lasting effects are, and what I can do from here short of taking it to a mechanic. Is there something else simple I can check & replace? Other system problems I should watch for?

Thanks, from a novice!

I can imagine no way that a fuse would cause that type of problem. They either work, or they don’t. A fuse could cause a melted wires, maybe even a fire, though, if a larger one was used than needed, as was done here. But no damage done, it seems. Your 27 year old car may just have a worn out turn signal switch. Where, exactly, is the noise coming from?

Yikes! If it fried a 25 amp fuse where a 15 amp fuse was supposed to be, you’re driving an inferno looking for a place to happen!

No, the smog guys didn’t do this. And no, it didn’t start making the noise the day you bought it. The previous owner… or the one before him… knew he had a serious electrical problem and put the 25 amp fuse in there to sell the car and get rid of it before the fire happened.

I strongly recommend that you find a shop that specializes in automotive electrical systems and have the car towed there. If you drive it there, which I don’t recommend, bring a tri-rated fire extinguisher for the ride.

The danger of using a higher-amp fuse than you’re supposed to is that something will catch fire or be irreparably destroyed by the overcurrent. The fire didn’t happen, and now that I assume you put the proper amperage fuse in there, there shouldn’t be any further danger going forward (ok, a slight danger, because it might have melted wires that will now touch, but that is extremely slight because in 1.5 years it would have happened by now).

That said, if it blew a 25 amp fuse, it will probably blow the 15 amp fuse, so if you haven’t found and fixed the problem, it’s likely the new fuse is going to blow, if it hasn’t already.

I would start by inspecting the wiring harness that’s located near the driver’s side trunk hinge. Your car is famous for getting damage to that harness, because it’s too close to the moving parts, and gets stressed/rubbed every time you open and close the trunk.

It wouldn’t terribly surprise me if your turn signal is screaming because of a short, too.

This is definitely something you need to address - dead tail lights are not only dangerous to you and others, but driving an car with unsafe equipment exposes you to legal liability should a wreck happen.

Honestly, I’m not sure. I’ve never had so much trouble pinpointing the source of a sound. Probably from the steering column?

At least to this part I can say I have some degree of all my turn signals. I’ve watched their reflections in windows & had others look at my rear lights. I’m not sure what’s missing, but there are indicators for each turn signal.

So the main theory is that someone deliberately installed a higher amp fuse to cover up an existing problem, and that may or may not have melted other wires? Because the fuse was blown, I was in less danger because it couldn’t make a solid connection?

Kelley Blue Book only went back to 1992 and it looks like your vehicle is only worth $1000 if you sell it your self and with all the problem that is most likely high. You can do what you want but I would just let it go.

That’s where the turn signal switch is. I don’t know how hard it’ll be to replace.

I have an uncle whose repairwork I trust; he said once it was likely that, and that it wouldn’t be hard (for a shop). I’ve just never managed to get it done. There are all kinds of reasons why this sound can be made, from shorts to blown bulbs to signal switches to sheared bolts in the steering column. I’ve spent a lot of time researching this problem, just haven’t fixed it.

In some ways she’s an insanely reliable car, I just can’t manage to prioritize what to repair. $300 for the rear struts? Unknown amount for the sweet spot on the turn signal? $200 to replace the broken windshield? Fix the broken driver’s door handle & window that can’t be rolled down? She runs like a charm & is totally silent when running, which is lucky because she’s all I was able to find when I was buying a car. She’s also got 345,000 miles.

That’s my theory well articulated.

I don’t subscribe to that theory. Because the circuit in which the fuse blew is now an “open” from the fuse on does not mean that it isn’t shorted prior to the fuse location… or even in another line.

The only thing we know for sure is that a circuit designed to carry no more than 15 amps was, when the 25 amp fuse was in it, carrying greater than 25 amps. Fires have started this way. We also know that this circuit is fed by the same battery that the other circuits are, thus it was not and is not isolated from the rest of the vehicle’s circuits. Therefore, if something is shorted anything could be happening.

Thank you for those descriptions. My understanding of electricity is very poor.

Let me see if I understand this right. That the fuse was bad definitely, absolutely means that it is ‘blown’. A blown fuse can only happen from too many amps going through it. It is most likely that that was not a one-time overload. That overload most likely happened from a short that is still active, and will take out the new fuse as well. Being a short, it may do nothing, it may take out the new fuse, it may blow a larger system, it may cause a fire and be very bad. Do I understand right?

You’ve got it. With a blown fuse, whatever was on that circuit wouldn’t be working. What would that be? What circuit is it?

I don’t have a number of these (like cruise control), and several are controlled by multiple fuses, like the clock.

I expect you already know that the fuses installed should match what the owner’s manual says. Too big can cause problems, too little can cause problems. Suggest to simply replace any that don’t. Hopefully everything will work and nothing more to do about the fuses. If not then solve any resulting electrical problems one by one as they come up.

My own similar vintage Corolla had that screeching sound problem happen last year when turning left (but not right). I was able to fix it – at least temporarily, still working ok – by spraying some electrical contact cleaner into the switch internals. If the contacts don’t have low enough “on” resistance, it prevents the blinker relay (the source of the click) from working properly, and you get the resulting screeching. The proper method is to replace that switch, but doing that might not be so easy, probably requires removing the steering wheel. And sourcing the switch ass’y might prove difficult too. If yours is like mine the left and right side lever-gadgets that stick out from the steering column are actually both part of the same switch assembly, called the multi-function switch. It’s a pretty common failure item reported here, on all types of cars.

I am more proud than I should be about guessing the fuse was the wrong size to begin with. I did this project to begin with without any fuse box diagrams. I had no book and my kickpanel cover was gone. I googled how to tell a fuse was bad, then took out each one & checked them. I bought new 25 amp fuses, but I was suspicious–in searching for a diagram I had looked at several years of Camry fuse diagrams, and not a single one had a 25 amp on the interior (or anywhere else). I asked the guy at the auto store, who couldn’t help. I came home, couldn’t shake my suspicion and started looking harder to find a proper fuse box diagram. I was elated when I found one and my suspicions were proven right. I replaced the fuse, but then had concerns about if it caused more damage, so I came here :slight_smile:

You my friend seem to be the Columbo of fuses :wink: .

You can probably download a free pdf copy of the owner’s manual for your car from the main Toyota website.

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You mean several items are controlled by a given fuse, right?

No, in the best diagram I’ve found (you’d be surprised how hard it is to find a good one) the clock is listed in three different fuse controls. My clock worked without the fuse.

This justanswer “fix your car” link is to the fuse diagram, not an ad.

I should probably add the photo I found of the kickpanel, too. I couldn’t comprehend the above fuse diagram until I found this kickpanel diagram, which corresponds perfectly to my car. I made sure of that after all this lol.

Install a new 15 amp fuse and see if the tail lights work. If the fuse blows inspect the wiring harness and bulb sockets for damage/shorts.

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Then there are three possible ways the clock might be wired, or three possible clocks. In no case is a single item in your car, like the clock, powered through more than one fuse.

Thanks for the explanation :slight_smile: I don’t know about newer cars, but my love of 1990 foreign cars gets me in trouble with all the variety they’re made with. You’d think they’d all have the same parts & be wired the same.