blowing fuses

ray humbel · #1 (**permalink**) 10-12-2010, 11:38 PM

i keep blowing fuses on my 4000. it is the fuse for turn signals, brake lites and tach. i've changed all 1157 bulbs twice. checked the grounds. changed the flasher twice. checked the bulb sockets. the headlites,tail and parking lites are all working ok. any suggestions?

RICK LAKE · #2 (**permalink**) 10-13-2010, 04:17 AM

ray humbel a power and ground wire to the back of the car. If you have a full trunk with rugs or metal, the most common is putting a screw in the wrong spot and getting this over time. The vibration has worn a hole in the insulator and you have a short. There are kits for finding shorts, I have never had much luck with them. The easiest way to find a short, AND I DON'T RECOMEND THIS is to bypass th fuse and run direct power to re bulbs and switchs. use them and have your finger on the wires, if you feel one get hot quick you found the bad wire. You can get burnt doing this. If the wire is just nicked it will burn the wire touch ground and burn away. The system will work again until the wire moves toward the ground contact spot.
If you have an ohm meter and get luicky you can unhook each wire and ohm it out. to ground. You will need to unhook the battery to do this. Ground of the frame to each wire going to the back of the car. If one pops up with resistance you found the winner. If they are all out of range or open to ground, you still have a problem. Talk to Shebly and see if they are having a short in the harness or rub some where. Rick L. Ps this is why mechanic get 2-8 hours for tracking wiring problems at dealerships and garages. This is the worst job to do and find the problem, gutting the whole interior to find a short. Some or easy, some are hard, work slow and have good eyes, 2 pair are even better. If all else falls, power up the harness and watch for smoke,

you will find the spot and run a new wire.

Jerry Clayton · #3 (**permalink**) 10-13-2010, 08:18 AM

I'd disconnect the tach to isolate it to either the tach or the lite system--

then--if its the lite system--first turn on the parking lites to check them, then just the brake lites, brake lites and parking lites,turn signals rt and then left, turn signals r plus brakes, l plus brakes--this should isolate exactly which area to look into--

On fiberglass cars/boats everything has to be individually grounded---I have found(on a SPF ) where at the right rear the wires were on the taillite in correctly and was feeding the hot wire to the common ground of one bulb---it would blow the fuse with the combination of turn signal, parking lite, and brakes---

The problem is probably at the socket for the bulb that lites up on braking---

vector1 · #4 (**permalink**) 10-13-2010, 02:48 PM

turn signals, brake lights, & tach, interesting combination. what size fuse?

FWB · #5 (**permalink**) 10-13-2010, 04:49 PM

what exactly in the tach are you protecting? or do you mean the tach light? wouldn't the tach light be fused with the rest of the instrument cluster? No?

or at 6000 rpm does the fuse blow?

ray humbel · #6 (**permalink**) 10-14-2010, 03:28 PM

the wiring diagram calls for a 10amp, seems a little light but that is what it calls for. turn signals,stop lites,tach function (not light) and fuel gauge are on the same 10amp. i put a 15amp in and i'll see if that blows. i have not driven the car yet. any and all idea's will be looked into. thank you.