blowing #5 fuse in 74 spider

Niels · #1 (**permalink**) 09-29-2009, 07:03 PM

I was inspired recently to get the tail lights working on the '74 spider. I had drivers side brake light, but the bulb was bad on the passenger side. Cleaned the receptacle, replaced bulb and bing I had both brake lights. Great start.

#5 fuse would blow as soon as I turn the stalk to first position. I replaced all the gauge lights and for a short (pun intended) time had everything working with the exception of side markers. Lights went out when putting nuts back on the passenger tail light. Jiggle with finger a wire behind the housing and all is on again, no fuse blown. Went for a drive and hit the wipers (on a different fuse) to clear dew and all is dark again and the fuse is blown.

Pull light out again, replace all the female connectors on the ground wire series, clean more terminals and the ground on the passenger tail light and everything works again until I put the light assembly back in the car with all the bolts. Blow the same fuse a few more times trying to track down a source of the short at the passenger tail light assembly. I swapped out a whole tail light assembly with a known good one from a '72 and the fuse blows again as soon as I turn the stalk to position 1.

My electrical tools are (is) limited to a test light, though friends have more and more knowledge of electrics albeit not on Alfas.

I've lived without driving evenings for 4 years now, but I'm hoping to make a long drive from Columbus, Oh to Winston-Salem, NC for work and would really love to take the spider. Any suggestions as to where to start poking around?

Thanks,
Niels

**andy303** · #2 (**permalink**) 09-30-2009, 11:12 AM

Niels:
Do you have a wiring diagram? If not here is a link to one for the 72-73 Spider which I think is almost the same: http://www.alfabb.com/bb/forums/elec...l-diagram.html

Scroll down and open and save the pdf.

The fuse blows when it is passing more current than it should because of a short circuit in the wires it supplies current to. When you turn on the parking lights you supply current to one side of the fuse shown by the single yellow wire coming from the stalk switch. On the other side of the fuse there are yellow wires supplying current to a multitude of interior and exterior lights anyone of which may be the source of the problem. You need to approach the problem methodically. Try pulling all the yellow wires feeding the lights at the fuse and reconnect each one in turn until the fuse blows. Then you will have isolated the bad circuit.

Niels · #3 (**permalink**) 09-30-2009, 01:45 PM

I found that and have a printout. I started to do as you suggested but chickened-out as it was dark and I caused a few sparks to fly. I'll try again...maybe with the battery disconnected. I'll let you know what I discover.

Thank you for the response.

**andy303** · #4 (**permalink**) 09-30-2009, 02:52 PM

If I read the diagram right there should be no current present with the switch in the off position. Sure, pull the battery negative cable then disconnect the yellow light circuit wires. Reconnect the battery. If there is current present at fuse 5 with the stalk in the off position then I would look for a short in the light switch itself. It is always "hot". If not, OK. Try reconnecting one yellow wire at a time with the switch off. If there is a spark from one of the yellow wires with parking lights off then there is a short circuit from another power source that is grounding through that wire. If no spark, fine, try the switch. If the fuse blows pull that wire and label it. Repeat the process with the other ones. Then go back and trace the bad circuit.

You mentioned the problem also occurred with the wipers switched on. I wonder if the ash try light or dimmer switch wires got pinched under the center console.

Niels · #5 (**permalink**) 10-01-2009, 08:21 AM

Well I pulled one of the 3 yellow wires off and turned the switch. Nothing, no dash lights, no tail lights, but also didn't blow the fuse. So at least I know which wire is blowing the fuse. I need to printout the wiring diagram again as I couldn't find it last night. I'm not sure what should have worked (2 remaining wires). Am I right to ignore that for now and instead concentrate in tracing the wire which I know blows the fuse?

Niels · #6 (**permalink**) 10-05-2009, 07:35 AM

FIXED! For now at least.

I'm not sure what the actual cause was...I was going through so many fuses that I decided to stop doing one thing at a time. Basically I replaced side marker bulbs, dash bulbs, cleaned connections at the tail light, cleaned grounds at the tail lights and courtesy lights under the hood and in the trunk and crimped on some new female connectors. I think the connection between the two tail lights was a weak link. Lastly, when one of the headlights stopped working I went through a pulled all the fuses and hit them with sand paper. Everything, well almost, seems to be working now.

I've had it for 10 years now and I get just as much pleasure driving it as I did when I first get it. Can't wait to drive at night again.

Thanks,
Niels

**andy303** · #7 (**permalink**) 10-05-2009, 10:41 AM

Niels:
Good work. If nothing new is amiss it was probably due to bad ground connections you fixed. I chased a problem in a front turn signal that turned out to be a simple loose screw that ground the left front light harness. If those electrons can't find the path that God and Alfa Romeo intended the little devils will seek their own way back to ground, through light sockets and just about anything else conductive.