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Discussion Starter · #1 · (Edited)
i have searched and have not found a thread on this particular issue
just picked up a1985 spider today
good condition all was working
but on the way home the Alternator /battery light came on no change in running so i am thinking great battery or alt but then noticed that the Tach drops to zero when the battery light comes on
i have checked connections to the battery the car starts fine no slow down in turn signals or wipers just The battery light and no tach
the tach will come on intermittantly and the light goes out
but then the problem re-occurs sounds like a wire or connector shaking loose
any guidance on where to start looking ??
 

· Trained (ex)Professional, , 1953-2018 RIP
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16,230 Posts
Welcome Jeff and congrats on your purchase!! :)

First thing I'd check would be fuse #7. Ensure that it is tight in the holder and that the connections are clean (a pencil eraser works well). Actually, check/clean ALL the fuses (not that Alfas have electrical issues mind you :rolleyes: )

Oh, and I'd recommend that you post some pics of your new Spider. Sometimes, that correct diagnosis requires knowing what the color is. (j/k)
 

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Discussion Starter · #3 ·
Thanks i am on thr right track
keeps blowing number 7 when it does i lose tach dash lights and fuel guage
my shop manual shows a 10amp in 7 car had an 8a
closest i found was a 16 amp did great for a few minutes the issue comes back

but i now have more trouble shooting info
all seems good at idle
alt light comes on tach and fuel gauge out on acceleration
de-acceleration all works great no l alt light tach fine and steady until i input throttle again the symptoms come back

my shop manual is for a1986-89 trying to make sense of it
any idea where to look first ?
battery is good charging system working
 

· Administrator
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I assume your '85 has the 'bullet' style fuses. Those type are known to look OK but somehow fail to actually pass electrons. I suggest removing all the fuses, cleaning the contacts (as Jim says, a pencil eraser works well) and putting in all new fuses. They could be over 20 years old. While you are at it, do the same for the fuel pump fuse. That one is in an in-line fuse holder located next to the FI computer under the parcel shelf behind the seats.

While you are cleaning things electrical, clean and secure the connections at the junction box on the left inner fender. It has 3 red wires & a pair of green wires. The red wires carry 12V from the alternator to the battery and the green wires are the sensing wires for the altenator light in the tach.
 

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Discussion Starter · #6 ·
replaced all fuses with new and clean contacts no loose wires or connectors i could find on back of fuse box
number 7 keeps blowing 8 amp

bullet style will do the alt connection thing but would that cause the other fuel gauge and tach issues?
 

· 1966-2013
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13,740 Posts
Hmm.

Tach is connected to coil for signal and another source for power.
Generat lamp is connected through the charging system.

Both are earthed via gauge head which in turn grounds at/to the gang of wires down at the lower left end of the dash panel.

Perhaps worth a looksee and clean of that bundle?

A constantly blowing fuse is kind of indicative of either a short, or an intermittant connection that likes to put spikey loads on the circut.

Query: what do the 3 gauges in the top of the console do when the tach is off and the light is on?
 

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Discussion Starter · #8 ·
fuel guage goes out down to empty did not look closly at others tach is "jumpy" befor blowing i like the loose ground thing will try to fund it when the rain stops
 

· 1966-2013
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13,740 Posts
fuel guage goes out down to empty
Ah, that's something of note.

Might wanna check the ignition switch connections at the bottom of the column as the fuel gauge 0'ing leads one to think perhaps the switch is losing contact either in the wiring or the switch head proper.

With power off, the fuel and oil pressure gauge will head down toward 0 while the temp gauge will move toward the center of its range regardless of actual temperature at the time.

With key on and engine off, the generat light does indeed come on, and its possible to have the engine running but a certain wire or contact in the switch intermittantly connected.

For giggles, if you're driving and see it happening, but before the fuse pops, wiggle/jiggle the key to see if it has any effect.
 

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Discussion Starter · #10 ·
thanks for info so far here is what i have at this point

if the two wire into one connector coming from the starter switch
(red and green wire on one side red on the other) is disconnected the fuse stays intact
when hooked up
as soon as switch is in "on "position it blows the # 7 fuse and i lose fuel oil and water temp as well as tach and alt light coming on
trying on my shop manual to find where this goes but hard to follow their diagrams
i have looked as far as i can and have seen no bare spots or pinched wires
the frustration level is rising
 

· Trained (ex)Professional, , 1953-2018 RIP
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Ah HAH! The most common cause for Black Spiders with red interiors for blowing fuse #7 is a shorted lighter.

Try pulling out just the lighter element first. If the short is still there, disconnect the pink power wire at the rear of the lighter socket. This pink wire is one of two pink wires on fuse#7 that also powers the reverse lights, the fan and, are you ready? The gauges.

If you'd like a color wiring for your Spider, please send me a private message with your email address and I'll send it to you. :)
 

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Discussion Starter · #15 ·
thank all it was the lighter corroded
after a day living under the dash the 45 sec fix was welcome
may i WILL sell the motorcycle and keep the Spider
Many thanks and I am sure i will be back for more
pic s will be up soon :D
 
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