Gremlins in my electrical system?

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finnman1

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Anybody know off hand what would cause my tach to jump to 6k and blow the main fuse everytime i turn the ignition to the "on" position? the fuse gets red hot and then pops.
 
How long has the tack been in your car and did you install it?
Make sure the wire's through the fire wall and out in the engine area
have not rubbed through the insolation.
Or the tack may have a short in it.
Have you dun any new wiring lately?
 
the tach's fine... i just installed a new alternator, but i triple checked the install.. could it be the voltage reg?
 
no not likely the reg has nothing to do with the voltage as long as the key switch is only in the on position. Vehicle running then yes it has to do the tach in supply voltage only. If what you say is right then when you turn the key to the on position and it pops a fuse, it is without a doubt directly shorted to ground somewhere. Disconnect the tach and turn the key on does that fuse blow? start the vehicle up and check voltage of the alt. hook the tach back up does the fuse blow then? if so it's the tach. Disconnect the alt and start the car up does the fuse blow,,,,,,,, you get the idea now,,,, isolate each until the offending item is located then fix JMO


Good luck
racy
 
i'll try that... for the alternator... would you recommend disconnecting the hot wire only, or the whole thing. disconnecting the whole thing (all three wires) would cause it to not have a complete circut anymore correct?
also, the tach would jump to about 2k before...
 
you still have a complete auto circuit just not the capabilities to charge the bat if you disconnect all three. if you start the vehicle up and at idle you have between 12 and 14.5 volts your alts ok, revving up the engine should'nt change the output,,,,, thats why you have the voltage reg. In all just disconnect the hot wire. By the way is the reg seperate or part of the alt. what kinda vehicle is it?

racy
 
Take the tach apart. The two studs that stick through the back have an insulator that keeps them from touching the metal housing, which is grounded, which if shorted, would be a dead short to ground.
 
440 in a duster... mp elec ign w/ ballast resistor... reman alternator.
 
ok on the vehicle,,,,, do those things that were suggested by redness and I and get back to us.

racy
 
disconnected the alternator hot wire... no go. disconnected the tach hot wire... still no go. :tongue8: i looked at about every hot wire running through the engine compartment/ firewall/ under the dash for a breach in the insulator causing a short and couldn't find any.
 
Question? which fuse keeps blowing
and you said this wasn't doing this before you installed the the new alt?
 
its the fuse running into my gauge panel. so, starter, fuel pump, line lock and VHT washer bottle are all hooked up. i've checked all the lines running from each. the starter line is going into the starter relay switch on the inner fender. and come to think of it, i know this would have helped from the start, but i remember hitting the hot wire of the alternator to a ground which is initally what blew the fuse. everything 'seems' in order, that's why initially i wondered if anybody know off hand what these symptoms are causing.

the fuse does blow, but before, for about 3 seconds, it gets red hot, then pops. i tried turning the ign on and turning the fuel pump on real quick (electric) and the pump hummed at about half power...then the fuse blew like usual.
 
so if what i'm reading is, is that you shorted the alt to ground which blew the fuse the first time, If this is true take an ohm meter and check resistence from the hot lead out of the alt to ground and let me know how many ohms the resistence is,,,,,, you might have blown the alt and it might be grounded now. Does the fuse blow with the alt completely disconnected
 
If the alt wire was not connected when it shorted I would think no harm done to the alt. For the wire itself......I would double check it with a meter to ground for continuity. Just like racy said.
 
buy buy buy! ive went through about 155 fuses and now i have to buy an ohm meter! :happy6::thefinge:
i presume red wire to alternator hot, black to ground such as clean/non painted engine block. ive never ran one of those things. wonder what setting the dial should be on.
 
no lol you don't have to buy one if you don't have one ,,, take the alt to a shop who'll test it for you and tell you if it's ok. Sorry. And if the wire that you touched to ground was the wire off of the alt it could be that the alt is ok. It is kinda tough trouble shooting over the net you know.
By the way where are you located just out of curiosity?
 
it wasn't touching...or so i think. yes, it is next to impossible to diagnose online. man i wish i had easier issues w/ my car, as most others on this site have simple fixes. it's just a little perplexing as the hot wire on the alternator goes into the starter relay dealio, then into the fuse then into the toggle switches... it could be a fried relay, but after that, if that's NOT the case; the hot wire is linked into basically the whole car, and anything could be at fault. maybe i could figure it out w/ a better knowledge base of electrical current and how it flows. idk
waterloo, iowa
 
ok the question that has still never been answered, did it have a problem popping fuses before you installed new/reman alt. If not then we will go from there Ok?
 
is this a fuse in the stock fuse box? or a secondary inline style? on the circuit that pops the fuse, what all is on that circuit? what size fuse? black wire to ground on the alt? what size is it? you should have 3 wires, thick black, green w/spade, and blue w/spade(only with later regulator/alternator setup)
 
sorry, didnt pop prior to alternator installation.....the black wire is actually a 'painless wiring' purple wire now, and it goes to the firewall block connector dealio. the connection is fine there... after that, i forgot... a little hung over... the dash lights work, the fuse is from the toggle switch panel, the switches (fuelpump, linelock, vht motor, and ign) work fine if the key is in the "off" position, turn it "on", and the fuse shorts out. fuse sizes ive tried all the way up to 35.
 
Odd, Same exact thing is happening to our 72 dart. Just one day the fuse started blowing when the ignition is turned on. Same fuse, the one that runs the gauges. The only thing that we noticed was the main alternator wire and come loose. But the problem still exists.
 
ok then that really helps on the diag. be 100 percent sure that the alt is wired correctly. REMOVE ALL THREE WIRES OFF OF THE ALT isolate them and turn the key on, if the fuse pops then you have something downstream bad,(but we'll get to that in time). If the fuse does not pop you have a bad remaned alt that is probably ground internally or it might be wired wrong, I'm not saying that it is but? I've been in the generator business for 16 years and I've seen weirder things

racy
 
okay, we'll do tonight... will post results on friday when i get back to the computer.. oh please god! :angel7:
 
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