my 1981 f-150 continues to blow the fuse that goes to the battery from the altenator. I also put in a 30 amp inline fuse to the selinoid but continues to blow the fuse , only when the battery is a little low. Got a new altenator and still have the same problem. Been going on since January of this year. Have been through the wiring system but can't find the problem.. if the battery is fully charged the fuse will not blow. Help!

 

I would replace the starter relay. It may be bad/shorting inside!

 

There is a fuse between the alternator and battery? How could a fuse handle the 90-150 amps that an alternator can put out? And a fuse between the battery and solenoid? Doesn't a start motor draw hundreds of amps? Perhaps I'm mis-understanding what fuses are being discussed.

 

Voltage Regulator puts out too much amps would blow the fuses and burn up wires....

 

Thanks, i have this past weekend purchase the wire that comes from the altenator to the selenoid with the oem fuse link. But the wire still gets extremely hot, however as usual, i took the battery to advaced and had it fully charged(battery got low because my brother left the switch on) and put it back in the truck. And the truck runs fine, airconditioner, lights and every thing else will run on the 30 amp inline fuse as well. In the past i have changed evry electrical part - voltage regulator(three just to make sure) new altenator(65 amp) electrical module, switch, light switch and so forth. Still have the problem that first started when i was boosted in January. Even if i run a direct line with no fuse still gets TOOO hot. To conclude, as long as the battery is fully charged the truck runs great and want run the battery down. I have been driving it to work for months with no problem, but of course, i don't leave anything on that will run the battery down while it sits for the day. Im desparate to find this problem.

Johnny

 

It sounds to me like something is wired wrong. If I remember right (from my previous '82 F-250), there should be a very heavy wire directly from the battery to the starter motor. Another wire from the battery goes to the relay which then goes out of the relay to the solenoid on the starter. I don't remember there being any fuses on any of these wires and none of them should get extremely hot. The relay is mounted on the fender well and is energized by your ignition switch. This connection is fused. The alternator wire should go direct to your battery and not to the starter.

If a wire is getting too hot, something is shorting. I am not sure which wire you are saying gets too hot. You state the one that goes from your alternator to your (starter?) solenoid, but I don't think that is the way it is supposed to be. Perhaps it goes to your relay on the fender.

Do you have a wiring diagram and is everything like the diagram?

 

A charging lead goes from the alternator to the battery side of the solenoid on the fender. Another lead goes into the harness and up to the fusebox.
Several items attatch to the battery side of the solenoid on the fender w/ fuselinks. Among them is the EEC and possibly the fuel pumps.
The fuselink is I believe a 14ga fuselink for the charging lead.
The wire will get hot if your battery is low. Not suppose to charge a dead battery with these alternators. They are only rated to maintain charge and run accessories. These trucks are equipped w/ a 65-65 Amp alternator standard. Max output is only obtained when running down the road above 2000 RPM typcally.

I left my lights on recently and completely drained the battery.. Jumped and took off down the road. By the time I got home the fuselink was melted. Replaced with a Maxi Blade type fuse rated at 60 Amps. Don't go larger than your alternator can output. Most mechanics don't recommend fuselinks.

Also, have your battery checked. Hard charging a dead battery can cause heating and damage to the plates inside. The battery is likely to fail if not properly charged (not the alternator) from a dead state.

If anybody knows of a large alternator that will fit without too much fabrication, I'd like to know. A 3G / 170 amp alternator from a Grand Marquis of the same vintage would be nice. I don't know why Ford went with these wimpy alternators. No extra capacity for additional loads on a truck is not a smart design.

 

I can get a 130 amp alt, for my 1977 Ford 351w and 1986 Ford 302 EFI. I use them both to run an 120 V AC Inverter with no problems at all, They will both charge an 600 amp Marine Battery with is in both units. Also change out the Voltage Regulator to be able to accept the charge from both Battery's at the same time....all on regular Fuse Links that came with the wiring.

 

Thanks. I really have nothing left to change. Don't know what to do. Hey, is your fuse link to the selenoid a 14 gauge wire?

Johnny

 

I know, back from the dead.

I think may be my fuseible link in the wire from the alternator to the battery is bad. Looks like it is a 14 gauge fuseible link ? 1986 F-150 302 V8

Here's the story. The alternator smoked, melted the two wire connector and the three wire connector. I was able to unplug the two wire connector from the old melted end that came out of the old alternator. That came apart cleanly.

The three wire connector was melted pretty bad and fell out of the old alternator. The smoke stopped when I shut off he engine. I have installed a rebuilt 65amp alternator from NAPA along with the recommended new three wire connector spliced into the harness going up to the fuseible link. I cut and spliced the wires one at a time so I didn't screw that up.

When I started the engine, the amp meter in the dash is still showing discharge. I thinking the fuseible link is bad ? With the engine running and my voltmeter on the battery terminals and can watch the voltage drop at the battery post.

The fusible link has one black wire going into it and three wires coming out of it, a black, a yellow and a yellow with blue strip.

So I'm I correct in thinking the fusible link is bad ?

Is there anything else I should check ?

I'm I correct that it is a 14 gauge fuseible link ?

I assume I can get one from an auto parts store, my local NAPA didn't one, and splice it in to replace the old one ?

 

It sounds like you have 1 of them 2G fire starter ALT on your truck, what year is it?
If it is the fire starter one I would go with a 3G ALT and the needed upgraded HD wiring & fuse.
Look on here for 3G ALT swap.

It see of the fuse link is good or bad you need an ohm meter. Disconnect the batt. put 1 klead on the ALT batt. stud and the other on the solenoid stud on the batt. cable side.
If the wire is good you should see it on the meter. If no movement on meter then bad fuse link.
The link is at the solenoid end between eyelet and the rubber block just down a little from the eyelet. If you were to arc the fuse link if it makes a sharp bend it blew the fuse part and needs to be replaced.

Most auto parts stores should hav ethe fuse link with the eyelet in place and a butt connector. I would cut the old link out, between rubber block and ALT.
DO NOT use a in line fuse like the OP did as it will blow like he had.
A normal fuse is made to blow fast when the power thru it goes over the limit.
A fuse link wire is a slow blow fuse. It can handle a little over the limit power thru it for a vary short time. Like when you first start the motor the draw on the batt was high and to replace the volts used the ALT will put out a lot of power at first start then cuts back to normal power out put.
It is the high output when it would blow a normal fuse.
Dave ----

 

1986 f150 302 v8

Thanks for setting me straight on where the orange 16ga fuseible link is. I was getting caught up with it being that 1/2" round 1" long thing in the harness off the alternator.

Sorry, I'm bad with Electrical,
What is this ? "put 1 klead on the ALT batt. stud"
Are you telling me I need to use the 2000 Ohm scale and get the red lead from the volt meter onto the output of the Alternator, put it in the connector on the middle slot ? And the black lead on the stud on the solenoid ?

 

Here's some pictures,

 

I think that's what you were saying to do ? I figured out a way to do it. ?

So the meter reads zero, that means the link is bad ?

I think I'll splice in the new one with a blade crimps, male/female so if the new link doesn't work I can put the OEM one back in.

 

So I installed the new fuseible link, on change.

I removed the alternator, had it tested, it good.

Are there other fuses in the system I'm missing ? I checked the under dash fuse box, not much in there.