Fusible Link short off solenoid?

[DESA]

Gone and done it   I've got a problem with a Fusible link off my solenoid melting in half every time i start and run the engine. SO lets start with what I've done lately concerning electrical that might give others an idea. First I installed a brand new battery with new Positive and Negative Leads, I wanted to do the H4 light conversion for better visibility at night ordered and installed 4 new Lamps and Bulbs (60/55W) also installed a pre fabricated wire Harness for a H4 headlight system with dual relays. Cut and spliced the new harness into the green and white wires coming from the switch that controlled the original headlight system and attached the fused positive lead directly to my battery to the relays in my new harness.
Lights worked everything operated great High/Low/On/Off Drove the car fro two days and decided the lights were not the best I figured because I had ordered a cheap set of Bulbs, I decided to try the GE nighthawk Platinum H4-60NHP Bulbs these are rated (60/55W) also Swapped out the bulbs for my low beam lights only flicked on the switch without the car running and everything looked great noticeably brighter   I had to pick up my girlfriend So I drove down the street and  3 blocks away the car dies pop the hood smell electrical and notice the fusible link off my solenoid had melted in half? I figured for sure I overloaded the system somehow with the new bulbs but my headlights worked fine and nothing had shorted in that circuit. the only noticeable thing was my under the hood light was out with the hood open and no cranking when I turned the key..I did a quick roadside patch job on the link and the hood light light up and when I cranked the key the car started right up of course within a few seconds the wire cooked itself and I was dead in the water again...I guess I'm asking does this sound related to the headlight system If so wouldn't I lose my lights in that circuit with this link overloading? i unplugged the entire headlight system and tried again patching the link and starting the car still it shorts and melts the wire? Here is a picture of the link that's frying its the obvious open wires near the solenoid please remember that a quick roadside repair was done on these wires that explains the bad looking job.

 

[eaglefreek]

You've got a short somewhere. I think it's just a coincidence that it happened a couple days after the light upgrade. Try chasing the wire and see what it powers and go from there.

[DESA]

Well still having trouble with this? I bought some new fusible link and did some searching in the TSM manual Pg C-144 has a Table explaining the Location Color size and what that links protects..
this is a list of what they protect:

1: Headlamps/Heated Backlight (Red/16 ga)
2: Horn Circuit (Pink/20Ga)
3: Ignition/Power Optional Engine Compartment Lamp/Decklid Release (Red 18/ga)
4: Power Options (Red/18Ga)
5: Alternator Output Wire (Red/14ga)

The Link that Fries on me (green wire) Has a Factory Splice into two red wires one larger than the other, I spliced two new pieces of Fusible link to both wires and attached them one by one the smaller one controlled the Engine Compartment light for sure it lite up no problem but still no Ignition/Radio or power windows..I attach the second larger wire with new Link and all is good radio power windows all work wire stays cold nothing heats up. As soon as I crank the engine the car will fire up no problem the Bat/Alternator light in The Dash lights up Dimly and the Fusible link heats up real fast I have a partner to quickly disconnect..

I am still confused with what is shorting out and why it only happens when the car is running? Also my Fusible links don't seem to match up with what the TSM says although everything looks stock? Am I wrong thinking this could be an Alternator Problem possibly explaining why it happens when The engine is running?

[eagleman]

Where's that spare alternator when you need it huh. Kinds sounds like the armature may be shorted out.

[eaglebeek]

Eagles were originally equipped with a solenoid on the crankcase vent hose at the manifold. The solenoid was a subject of a factory recall in (I believe) 1985. The dealer removed the solenoid, connected the hose directly to the manifold and tied up the wires. One of the wires going to that solenoid was hot at all times. The other wire grounded the solenoid through the computer, thereby actuating it. I'm wondering if that harness has somehow made contact with the hot exhaust manifold and shorted out. If so you would find it on the manifold just behind the carburetor.

[DESA]

Well I've Isolated the the problem wire obviously because It melts in half I traced it back to the main wire harness that enters the firewall from there I'm stumped without pulling the dash and following from there I tried to find wiring diagrams on eaglepedia but can no longer log in? I just don't understand why it only fries when the engine is running

[BenM]

That one that burns is the main power for the ignition. It must be something that goes on while the engine is running... something that probably isn't fused.

Did you pull all your fuses anyway to see if one is shorted? It's possible if unlikely, but easy to check. And see if anything looks weird there; several wires plug into the panel to power accessories so there are some hot connectors there.

I'd also suggest pulling the plug off the oil pressure sending unit (that disables the choke & manifold heater). When a heating unit burns out it can short, and the manifold heater already draws a lot of power. I'm not 100% sure it's on that link, but it's a start.

BTW, what are the other two wires on the stud going to?

[DESA]

WOHOO Ben we're onto something Buddy! I did like you said Unhooked the Oil pressure sending unit and the wire that I assumed was the manifold heater (goes to the bottom of the manifold mine is a red wire) with both disconnected she fired right up like normal. with my fingers on the link I notice no heat at all this is good   So I attached the oil pressure sensor wire harness and left the manifold heater unhooked. Started the car while holding the fusible link and right away it started heating up fast!..So I assume now I have a bad Oil pressure sensor and this is what is causing the short? As for choke heater I no longer have the Original Carter I use the Motorcraft 2100 with a full manual choke set up.. what do you think am I on the right track with the oil sending unit being wrong?  

[Jurjen]

I think the oil pressure sensor supplies power to the electric choke pull back, so w/o the choke heater where that wire ending now?

[BenM]

Possibly. The three suspects are that switch, the manifold heater relay, and the choke.

It's a separate wiring harness. There is a plug that connects to the main harness so you can pull the whole thing out and examine it if you want. If I recall correctly, it's a small flat connector that looks very similar to the steering column connector.

In the meantime if you have to, you can drive without it; your choke will open really slow and it might be a bit unpleasant until it warms up.

So that oil sending unit is a weird little item. There are three pins, two connect to each other at a very low oil pressure, I think about 2-3 psi. That routes power to the choke and to a relay for the manifold heater. The other pin is a ground for the oil pressure light on the cluster, which I think is around 8-10 psi.

There's the possibility that the sending unit shorted, or some of the wires are crossed or shorted.

The relay and choke heater get the power that is switched by the sending unit and the relay is grounded through either the sensor in the back of the intake manifold that has one threaded terminal coming out of it or the sensor (not sure which hole) that has three pins and a special connector. That depends on the year, the early years favored that three-pin sensor.

The temperature sensor disconnects the ground to the relay around 160 deg to turn off the manifold heater.

So, check those places and the wires connecting them. The sending unit usually fails by leaking oil directly onto your exhaust manifold and smoking out everyone behind you.

[ammachine390]

You can narrow it down a little further too. Right by the starter solenoid there should be 2 relays. One is the horn relay, which I believe has 3 pins. And the other more square one, that is 4 pins, is the intake heater relay. You can try unplugging that relay and see if your fusible link still gets hot. If it does, then the problem is in the choke unit, or the oil pressure switch. If the link doesn't heat up when the relay is unplugged, then the problem is somewhere in the intake heater circuit. I would say the most likely problem then would be that the power wire for the intake heater got burned on the exhaust manifold and is shorting out.

[DESA]

You can narrow it down a little further too. Right by the starter solenoid there should be 2 relays. One is the horn relay, which I believe has 3 pins. And the other more square one, that is 4 pins, is the intake heater relay. You can try unplugging that relay and see if your fusible link still gets hot. If it does, then the problem is in the choke unit, or the oil pressure switch. If the link doesn't heat up when the relay is unplugged, then the problem is somewhere in the intake heater circuit. I would say the most likely problem then would be that the power wire for the intake heater got burned on the exhaust manifold and is shorting out.

Ok Found the Heater Relay (four wires) Unplugged the relay and left the Oil pressure switch plugged in started the Car and the link stayed Cold everything else ran fine.. So now were back to saying its this Manifold Heater circuit, although when I unplug the wire going to the manifold heater (red wire that travels to the bottom center of the manifold) with the relay plugged back in the link still heats up, So I take it now the short is before the actual heater itself but still in that circuit, Could it be the relay itself is toast? As for the Choke heater like I mentioned I run a full manual operated choke system attached to a Bare bones Motorcraft 2100 the original wiring to the automatic Carter Choke has been taped up and tucked away from anything, its been like this for years now since i did the conversion..

This all starts to make more sense now seeing that the Relay for the Heater and Choke heat gets power from the oil sending unit this explains why the wire only shorts when the car is running and making oil pressure completing the circuit and giving power to the realy..( on a side not the car is an 88 and all the wiring to the manifold heater looks great no burns rubs or funny stuff)

[ammachine390]

It could be the relay itself. Do you have an ohmmeter? You can check the resistance of the relay coil, it should have a good amount of resistance. Unplug the relay, and put the ohmmeter to the pins (on the relay) where the green and blue wire plug into. If that check out good, put the ohmmeter probes into the red wire pin of the relay harness, and a ground. If it shows close to 0, there's a short in the power wire to the heater itself, note, the heater itself has pretty low resistance. Would be good to unplug the heater, where it connects to the manifold, and then do that test, ohmmeter should indicate an open. Then check the resistance of the heater itself at where it plugs in, should have some resistance, can't remember how much though.

[DESA]

Replace the Relay with a brand new one started her up and   we're in business No more heating up of the fusible link everything is functional and I'm laughing. Excellent work buy all who helped me out with this problem, again I couldn't have figured this out without the Nest thanks so much.  

[carnuck]

It could be the wrong relay was put in at some time.