How to replace fusible links?

[boulky12]

(Headlights were working)- One day when I was doing a little burnout in my yard, the positive cable shorted out on the header and shut the truck off.

Once I rerouted the wire, all was good except the headlights stopped working (taillights, signals still work).

Since I checked all the connections, and cleaned up all the grounds, and my headlights stopped working AFTER the truck shorted, I believe it to be a blown fusible link.

The only ones I've seen are the ones by my starter, there's 2.
Are these the ones I need to replace? And how do I do it?

Thanks guys. Truck is a 81 350/350 swb.

[hatzie]

Look at the GM wiring diagram for your truck year.  I scanned all of my library to PDF and Chris hosted them on this board here--->http://forum.73-87chevytrucks.com/smforum/index.php/topic,25639  PM me if you need the 1984 wiring diagrams.

A blown Fusible link would cut power to far more than just the headlights.

This is how to replace a blown fusible link...  --->http://forum.73-87chevytrucks.com/smforum/index.php?topic=11972.0

[boulky12]

A blown Fusible link would cut power to far more than just the headlights.

topic=11972.0[/url]

So if you don't think think its the fusible link, then what do you think it could be?

Remember, that the headlights were working fine, until the truck shorted. Then they stopped working. But everything else still works? Even my wipers still work.

I also replaced all the broken fuses, still nothing.

[Kren420]

Did you check the bulbs? The short might have just burnt them out or something.

[boulky12]

Did you check the bulbs? The short might have just burnt them out or something.

I haven't. Has that been known to happen before?

[Kren420]

I honestly don't know was just a thought I had at the moment.  Trying to eliminate simple solutions first.

[jaredts]

I believe there is a fusible link for headlights and one for everything else at the starter.  A blown fusible link would kill just the headlights if that is correct.

[boulky12]

I believe there is a fusible link for headlights and one for everything else at the starter.  A blown fusible link would kill just the headlights if that is correct.

Do you know how I can find out which one is for the headlights?

[jaredts]

Remove negative battery cable and remove fusible link connection from starter.  You might visibly see that one is burned up.  If not, probe both sides for continuity with a multimeter.  At least that's what I would do.

[79gmc15]

I think it would be easier to plug a known good bulb in first before going down this rabbit hole of chasing fusible links.

[bd]

I think it would be easier to plug a known good bulb in first before going down this rabbit hole of chasing fusible links.

Or, use a test light if you have one and check for power at the headlamps.  Quick and easy!

If you have power reaching the headlamps, but they won't illuminate, check the headlamp grounds and the battery-to-radiator support ground.  Additionally, socket corrosion commonly interrupts electrical connection to the headlamp bulbs.  Unplug the sockets from the lamps and spray the contacts liberally with WD-40.  Then plug them back in and unplug them repeatedly, cleaning the connections.


FYI - there are three 6" long fusible links; two at the starter and one at the firewall junction block, above the engine next to the brake booster.  The link coming off the firewall junction block protects the headlamp wiring... but it also protects the tail & courtesy lights.

[hatzie]

81 schematics are in the back of the service manual and are not foldout pages.
According to the schematics GM used one fusible link with two outputs that feeds the headlights and the alternator at the starter.  The other fusible link at the starter is the main power feed to the firewall J-block for the everything else.  No-charging isn't in your symptom list.   If the alternator is charging the battery at 14.5v then you don't likely have a blown fusible link to the headlights as they are the same critter.

If you aren't getting a charge you probably blew out the 2 circuit fusible link at the starter.  Check for volts at the 2 wire plug on the alternator.  Also. Check for voltage at the dimmer and headlight switch.