Wowed, how to figure out fuse to use.

Wow I have this car that I am about to work on, and looking at it, this guy is asking for trouble the way he has it wired! He has pretty much everything connected direct to the battery unfused. I told the guy hey I will save you a lot of money, re-wire everything and fuse it properly for $40. Well I need to know one thing before I go at this, and that is how to figure out how to properly fuse some of the things that he has running to the battery. The Amps and the stereo are easy to figure out, but he has things hooked to his alarm with relays that are not fused, and other modules.

How do I figure out the proper fuse values for some of these items before this guys car lites up!?

Do I use this calculator?

Thanks for the help guys, as this is an old friend that I happened to run into whom I am trying to help out.

if unsure keep in mind that most standard relays are only rated 30/40 amps... so fuse each realy at 30 amps to be safe

-------------
Kevin Gerry
Certified Electronics Technician
MECP First Class Installer

Owner/Installer
Classic Car Audio
since 1979

That calculator will not work for you unless you know the "power" of whatever is hooked up. If you knew the current already you'd have your fuse size. kgerry hit the nail on the head with the relays.

With anything you are unsure of just start with a small fuse. Too small a fuse will not hurt anything, it will just blow if too much current is on the circuit (or a short). You can also put a DMM in series with any wires you have doubts with and check the draw. Start at the highest setting on your meter  (set to measure current of course) and work down. Some meters will have a seperate plug for higher current applications, if so use that first. However, if the wire you are testing is connected to something that is not operating or "on", you won't get the current reading you want.

Good Luck

-------------

thanks kgerry and master5, yea the relays were a big duh, but it is always better to be safe rather than sorry with a car that looks like burnt toast. . . lol

Your welcome, and it is VERY wise of you to be concerned about the lack of fusing.

Imagine if you work on this "burnt toast" car and the next day something you had nothing to do with decides to lay against the exhaust manifold or gets pinched somewhere. Now I don't know about your customers but mine would surely blame me, which is why I will turn down ANY job that has unsafe wiring unless I am paid to fix the probelms first.

I live in a land of DIY'ers and almost twice a week see the infamous 4 gauge ran through the fender/doorjamb area, swinging next to the exhaust manifold, unfused of course. Then I get the old "it's fused in the back..isin't that ok??"

I say "sure it's ok, if you don't mind one day standing next to your vehicle on the side of the road while it's smoking and burning", then you will be saying "would you look at that, wow, I wonder why that happened? ".

-------------

lol, well it is for a friend, so I'm trying to save him more than what he would be paying me, $40, which in my eyes is losing money, but for an old friend and possibly saving his life a heap of trouble it is worth it.

But man, I can just see you telling me that in person and the way I see it, it is really funny, because it is very true.

Yep, been there, seen that

-------------