Same fuse keeps repeatedly blowing.

turd_ferguson · 10-04-2008, 05:01 PM

Hi all,

I have a 2004 40th Anniversary edition GT 5-speed. 30K miles, and completely stock.

I've had the car for about 6 weeks, and with the exception of a loose baffle in one of the catalytic converters (for which I have a replacement on order), everything has been in solid working order.

For whatever reason, the under-dash fuse in slot 37 (Adjustable Illumination) blew the other day. I confirmed with my manual that the 5-amp fuse that was in there was the correct size. I replaced it, and an hour later, it blew again. Since then, it has started blowing repeatedly, every time I activate the dash lamps, as soon as I turn them on.

Now, I know that most of the other posters on here will be more than happy to post a reply like "It's a short". While I'm grateful for whatever help you guys send my way, this won't help. I'm hoping to hear from somebody who has actually enountered the same problem, but anyone who could provide a useful, thorough response in layman's terms would have my sincere gratitude.

To anyone who's going to attempt this: please let me know if there's anything I've omitted, or if there's any additional information you'd like.

Thanks again to all.

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mustangman281 · 10-04-2008, 07:41 PM

If it is indeed slot number 37 then that slot is for Radio, A/C-Heater control illumination, rear window defrost control switch, overdrive cancel switch, instrument cluster, and fog lams switch. It is supposed to be a 10amp fuse.

cliffyk · 10-04-2008, 10:17 PM

From the 2004 Owner's Manual:

Changed in 2001...

mustangman03 · 10-05-2008, 01:21 AM

Is their anyway you can get a hold to a wiring diagram to see what else uses that same fuse

cliffyk · 10-05-2008, 07:52 AM

It's powers all of the "dim-able" illumination, in series directly between the rheostat in the headlamp switch and the various illuminated gauges and switches...

In the shop manual it says:

Quote:

Function selector switch assembly, Rear window defrost switch (18578),
Instrument cluster, Transmission control switch, Traction control switch,
Radio (18806), Fog lamp switch

Here's the wiring diagram...

Where are you in MA? I lived in Plymouth and Osterville for most of my life, came down here (Saint Augustine FL) in '92...

turd_ferguson · 10-05-2008, 02:29 PM

Hi Cliffyk,

Now I live on the Watertown/Cambridge line, but I bounced around much of the south shore in previous years. Lived in Rockland until I was 15, then moved to Duxbury. Lemme tell ya, there ain't a more drastic change of pace than that. Since then, I've done Kingston, Hanover, Abington, Marshfield, Bridgewater, East Bridgewater, Somerville...all over.

Thanks to everyone who's offered input on my fuse issue. That wiring diagram would probably be a huge help if I had a clue how to read it...frankly, this stuff all goes right over my head.

I do understand the problem at it's most basic, but only as far as knowing that a fuse blows to prevent excessive amperage from damaging the car's systems. While I know that other components share this very same circuit, what confuses me is that nothing other than the adjustable lighting seems affected by the blown fuse. For example, the wiring diagram shows that the rear defroster switch is associated with this fuse. Both the defroster itself and the active indication light on the actual switch still work. How are they not affected by this?

As far as a remedy goes: is this something that someone with scant knowledge could diagnose in the driveway?

Also, is this the type of problem that is recorded in the car's diagnostic memory? In the past, any time someone I know had electrical problems with their car, it seemed that repair shops could never accurately pin down the issue (as such, I'm not thrilled with the idea of potentially investing my time/money in a few sessions of chasing one's own tail). Is this still the case, or have diagnostic systems finally reached the point at which they store a code that can direct a mechanic to the source of the surge?

blackstallion666 · 10-05-2008, 04:31 PM

sadly this kind of issue will not generate a code. Unless a sensor or module is affected by the blowing fuse. Since its seems to be a lighting issue most likly a code will not pop up.

simmy8 · 10-05-2008, 05:28 PM

I have finished my electrical classes at UTI, and from what it sounds like there is indeed a short. A fuse will blow if there is to much amperage flowing through it, and a short like that is usually a short to ground, so there might be an exposed wire somewere touching the chasis before it hits a light. Try following the wires from that fuse through out its entire circuit till you get to the original ground. Try to get your hands on a Haynes book. They have wire diagrams for every circuit in there. If all else fails, just take it to a shop, it doesnt' sound like it would be too hard to diagnose, and i doubt you will spend a lot of money. I will go on all data tomorow at work and see if i can find anything out that can help.

cliffyk · 10-05-2008, 05:32 PM

It is the night time illumination of the various instrument cluster and the switches that's powered by this circuit, not the indicators or the thing controlled by the switches--their are separate circuits for those.

That fuse ONLY feeds the illumination lights, and is in the circuit after the dimmer control, so it has to be an intermittent short or overload in one of the illuminated devices.

Is there any sort of aftermarket gauge, radio, whatever installed? Even something that might have been improperly removed by the previous owner?

================================
I was VP of Administration at Plimoth Plantation for several years in the 80's and early 90's, we brought Mayflower to Florida for the winter of 92/93 and I stayed. I miss clean air (there's a permanent musty smell here), real seasons (we have 2, summer and fall/spring)...

But I don't miss scraping and shoveling, and watching my car rust out, one damned bit...

turd_ferguson · 10-08-2008, 10:32 AM

simmy8
cliffyk

Thanks for explaining this stuff to me, guys. Honestly, it's still a bit much for me to wrap my head around, though. I thought I understood, at least in principle, how to read the basics of that wiring diagram; evidently I do not!

To Cliffyk--
To answer your question: no, everything is completely stock, as far as I can tell. I have the Mach 1000 system in my car, and although the head unit and cabin speakers are all stock, there is one detail about the arrangement in the trunk that might not be, though I have no way of determining this conclusively.

I know that countless '04 GT's came with the Mach 1000 system, but I've been told by some enthusiast friends of mine that the arrangment of sub-woofers and amps in my trunk is "unusual".

The image at this link shows what it looks like:
http://www.yellowmustangregistry.com...2/P5250057.JPG

I can't find much information about this arrangement online, but the display shelf and all the mounting brackets have a factory look to them. This would lead me to believe that this is not an aftermarket setup, but perhaps a factory custom order or a dealer-installed option.

I don't know if this would contribute to the blowing fuse issue, but if it in fact does, it seems strange that it would take 6 weeks (as a used car) to become a problem, and then suddenly be irreparable by way of a new fuse.

To simmy8--
Many thanks for the useful information, but as I've just eluded to cliffyk, a Haynes book would look as much like Greek to me as did your response. I proably will go to a shop, as you suggested, but I was hoping to know my chances before doing so. Were you able to find anything useful at work?