Confused by fuses

cheri1122 · Mar 24, 2009

So I got pulled in at the Coffee, Tn scale yesterday for a Level 1 inspection. Was feeling confident, until I turned on the lights (it was still daylight) and none of the markers on the box lit up - Murphy's Law, right? I got the sticker anyhow, as the blown fuse was all they found, but here's the thing: when I replaced the 15 amp fuse, I still had no lights. (Plus, I accidentally broke the wire for the satellite tracking system - o, darn!

). The tech who diagnosed the problem just put in a 20 amp fuse instead - something I wouldn't have done even if I'd thought of it.
The question is: why was 15 amps suddenly insufficient, after working for (presumably) years? What might cause that? And how do you know when it's ok to exceed the amperage of the fuse?

greg334 · Mar 24, 2009

cheri1122 said:
The question is: why was 15 amps suddenly insufficient, after working for (presumably) years? What might cause that? And how do you know when it's ok to exceed the amperage of the fuse?

Do you know if the fuse was good to begin with? Just because it looks good does not mean it is. I went through this with my turn signals last year, I replaced the fuse and still nothing. I got out a unopened box of fuses, put one in and it worked. I checked the fuse with a meter and it was open.

OntarioVanMan · Mar 24, 2009

Who said the 15 amp fuse was right to begin with?

And maybe a couple extra lights were added before you drove the truck and 15 was bare minimum...

cheri1122 · Mar 24, 2009

Greg: when the 'spare' fuse didn't work, I stopped at Wallyworld & bought new ones.
OVM: KW says - the diagram on the panel lists what each fuse controls, and the correct amps.
I'm just wondering why the 15 amp worked, then didn't - can't think of any changes made that might cause it, and I HATE mysteries!

spudhead911 · Mar 24, 2009

If the replaced 15 amp fused blew I would think you had a dead short in your wiring. If the 15 amp fused didn't blow but you still had no lights I would think that the new fuse was bad, I would have tried another new 15 amp fuse before using a 20 amp fuse. Its never a good thing to exceed the rated amperage(spelling)of the fuse, bad things can happen like to much heat building up in the wiring causing a fire. Using a higher amp fuse defeats the purpose of the fuse, which is to blow before serious stuff happens. I've seen it happen many times in my 25 years as a paid professional firefighter before becoming an expediter. IT IS NEVER OK TO EXCEED OEM SPECS FOR FUSES.

RLENT · Mar 25, 2009

cheri1122 said:
The tech who diagnosed the problem just put in a 20 amp fuse instead - something I wouldn't have done even if I'd thought of it.

Ahhh ..... don't think I'd be going back there - I'd say the "tech's" expertise leaves a little to be desired ......

Did they actually charge for this "service" ?

mjolnir131 · Mar 25, 2009

Yea putting a higher rated fuse in can lead to bad things happening like well, fires for example.You need to find out what the real problem is and have that fixed.

OntarioVanMan · Mar 25, 2009

What? Ya mean I can't wrap the fuse in tin foil and make it work anymore?

BTW Cheri...you mentioned breaking off the QC wire...where was it attached for power? Was it on an empty fuse of its own or did the installer just stick it into an existing one....some hack installers are known to do this and it can cause problems...

Jack_Berry · Mar 25, 2009

OntarioVanMan said:
What? Ya mean I can't wrap the fuse in tin foil and make it work anymore?

BTW Cheri...you mentioned breaking off the QC wire...where was it attached for power? Was it on an empty fuse of its own or did the installer just stick it into an existing one....some hack installers are known to do this and it can cause problems...

like turning on the driver airbag light? hmmmmm?

cheri1122 · Mar 25, 2009

Not 100% sure, but think the satellite wire was plugged into the same slot as the marker fuse - didn't pay it much attention till it broke, though. Have to go have the satellite reinstalled, will definitely ask some questions about where it's plugged in. I'm beginning to think it caused me to be cited on the inspection by blowing the fuse.

theoldprof · Mar 25, 2009

According to Dan, my electrician friend, if your wire terminals and connectors have any corrosion on them, that will have the effect as having an additional load. That could be why your 15 amp fuse worked and then didn't work. The corrosion works like adding a few more lights to a circuit. If you can, check ALL your terminals and splice connectors. Of course, the bad terminial will be the one you can't get to.

jsbiker · Mar 25, 2009

mmmm the best thing i can say is dont blow it, ........................

Moot · Mar 25, 2009

Cheri, what is it with you and marker light problems?

Never confuse a fuse with a fusee!

bluejaybee · Mar 27, 2009

I am going with theoldprof on this one. I had several marker lights that were corroded on the inside and when it would rain or when humidity was high, BAM, it would kick my breaker. Drove me nuts until one day I was replacing a bulb and noticed the corrosion inside the marker light. It will be on the hot side wire and have corrossion built up on it. When moisture is high, it lets the 12 volts drain off to ground and thus causes too much load for breaker (or fuse in cheri's case). I replaced that one and checked all the other ones. I don't remember how many I wound up changing, but it was several. After that, my breaker kicking stopped. Check inside your marker lights. I bet you will find the same thing.

cheri1122 · Mar 27, 2009

I will check the marker lights, at least the ones on the bottom.

When it stops raining. (Though it wasn't raining when or before the inspection occurred.)

bluejaybee · Mar 28, 2009

It just donged on me which scales you were at. You said Coffee, Tn. That is Coffee county and the scales are at Manchester. Wow! Manchester? And you didn't get a citation? You must be one slick talker to get out of that. That is an out of service to everybody else. I did 10 hours there about 3 years ago. The same ole drill sergeant female officer is still there, too. She spits on you when she is talking to you. Everybody knows Manchester on I24 is a toughy if they pull you in.

cheri1122 · Mar 28, 2009

Have to admit it was a surprise to get the sticker - even though it was clearly a blown fuse that I couldn't have known about before turning the lights on (it was still daylight), and every other t was crossed and i dotted, you still don't expect to be given a commonsense break by DOT - sad, innit?

bluejaybee · Mar 28, 2009

You have to have something going for you. I have heard there are a few at the Manchester scales who are nice, but to date, I have never run across one.

I was took out of service with no marker lights and I was told by a Tn state trooper (doing a roadside inspection), that in order for me to get back on the road, I had to call a repair truck to come fix them. I told him that I could fix them and he said fine, but a repair place of business would have to sign a repair ticket stating that it was fixed. I begged his pardon and started to isolate the problem with my markers. When I got them fixed, I pulled off and have never heard anything else from them. I sent the out of service notice and repair ticket in to the state, signed by me as the repair person.