fuses keep blowing on lights.
 

i have a problem. my lights wont work.

first thing i did was check bulbs. the one up front was no good so i replaced it. the one in rear i assume is good since i put a volt meter on the two connectors on the bottom and they had continunity.

i looked under the dash and fuse was blown. i tried to replace it and once it thoched the panel it blew. any ideas?

im gonna go and disconnect the front light then try a new fuse and then the back. any help would be great.

Re: fuses keep blowing on lights.
 

I'd say you have a short-circuit somewhere in your lighting circuit. Easy to check. You'll need a decent multi-meter, but that's a tool every boat-owner should have in his tool kit, anyway. Remove all lightbulbs. With the multi-meter set to measure DC voltage, check both sides of the fuse-holder. One side will measure 12VDC, the other: Nothing. Now switch the meter to measure resistance (ohms). Put it between ground and the side of the fuse holder that measured nothing. It should measure infinity, which would be an open circuit. I'm guessing it'll measure close to zero ohms resistance. Now all you need do is find out where the short-circuit is.

Try the resistance/continuity check with the switch for the lights both on and off. That will narrow-down the location of the short to "before" or "after" the switch. Try it with and without the rear light pole in-place.

Since the boat is, like, 99.999% non-conductive fiberglass, my guess is you'll find the short in one of the two light fixtures.

Jim

Re: fuses keep blowing on lights.
 

ok heres the news.
i pulled the stern light fixture then tried to put a fuse in. it blew

i pulled the front light fixture then tried to put in a fuse. it blew.

so that tells me i have a short either in the wires or on the switch or im runnig to small a fuse.(15amp) but i think it would have to be a short cause its blowin fuses even with no light fixtures.

and there is not a short in front fixture or the pole.

does anyone know which switch it would be cause since ive had the boat(3 months) the light have never worked. i have a 4 switch panel and it has to be one of the two left switches case the two right are courtsy and bildge.

im thinking of just running new wires. does anyone know how i would hook up new wires to switch.

Re: fuses keep blowing on lights.
 

At the rate you're going through fuses, you could buy a servicable multi-meter at Harbor Freight and be money ahead.

A bad switch would cause the lights to either be on all the time or off all the time. It has to be in the wiring.

A 15 amp fuse is more than enough for a couple of light fixtures.

When you say "no light fixtures," do you mean you literally removed the light fixtures, or simply the bulbs?

They aren't labeled? All the switches on our Mariah are labeled.

Seems a pretty easy process-of-elimation. But buy a meter, ok? Doesn't make sense to keep burning thru fuses like that.

Well... yeah. It's not hard. But neither is locating short circuits. If you can do one, you can do the other. If you can't do one, you probably shouldn't try tackling the other.

I've seen Amazon.com: Boatowner's Mechanical and Electrical Manual: Nigel Calder: Books recommended often. Perhaps you should pick up a copy of that, and a meter, before attempting to go any further?

Jim

Re: fuses keep blowing on lights.
 

Which lights are we talking about here? Nav lights or interior courtesy lights?

Re: fuses keep blowing on lights.
 

i have a multimeter. i just didnt have it on me. fuses are cheap.

ill hit it with the multi tonight.

yes fixtures were removed not just the bulbs.

both left switches say acc.

Re: fuses keep blowing on lights.
 

nav lights courtesy works

Re: fuses keep blowing on lights.
 

You are more than likely looking for a short in the wiring, but it is possible that there could be a screwed up connection/short at the back of the switch. The switch on mine is a rotary 3 position (nav/off/anchor) with a ground for the switch indicator light. Yours could either be rotary or a 3 position toggle with the same functions.

Dash schematics: http://www.mariahownersclub.com/foru...read.php?t=116

Re: fuses keep blowing on lights.
 

You'll need to understand how such a basic circuit works. I'll try an "ASCII art" drawing:

+12VDC ------- fuse ------ switch -------- load ----- -12VDC (ground)

(Where "load," in this case, is your lights.)

So all the fuse and switch do are open up the 12VDC positive path to one side of the light. Somewhere you have a short-circuit between 12VDC+ and 12VDC- (ground).

If you examine the fuse block carefully, you'll see one side has a strip running along it and the other side of each fuse holder has a Faston tab for connections. The side with the strip is the +12VDC common bus. The other side of each fuse holder is the load side. So, with the fuse out, if you measure resistance between the load side of the fuse holder and ground, with either the switch off or the lightbulb out, you should measure an open circuit (infinity). I'm guessing you'll measure zero resistance, which would be a short. But it there are dash lights (for the gauges, etc.), on the same circuit, it might measure very low resistance. (See "This confounds me," below.) Unless the short is between the fuse and switch, you should be able to use it to figure out which switch is the one for your nav/anchor lights.

There could be several things being the "load" (e.g.: nav light[s], anchor light, gauge lighting) and there could be more than one switched circuit on a fuse. (I tried to draw these, but the darned proportional fonts won't let the spacing come out right.)

You're going to have to do some painstaking wire tracing to figure out how all that was wired, I fear.

Well, you know it isn't the fixtures, then.

You just need to trace the wiring and find the short. Going by the simple diagram I did, above, you should be able to get it.

Here's what confounds me: You say you have only four switches, none of which are labeled as nav or anchor lights? That was a weird thing for Mariah to do. Of all the small boats we looked at recently, I can't think of a one that didn't have a switch complement like our boat has. Our '94 182 Barchetta has... um... five: blower, bilge, anchor, nav and courtesy on the left side. (Plus blanks for "acc" and something else I can't recall on the right.) So it's kind of sounding like the boat never originally had nav and anchor lights (hard to believe) and a previous owner added them and wired them up to an accessory switch?

In fact: You have no bilge blower??? :eek_animated:

Can you show us a picture of your dash?


Jim

Re: fuses keep blowing on lights.