1977 f250 electrical problem
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1977 f250 electrical problem
Ok so we just got my son a 1977 f250 i6 2wd 4 speed
i ran it and drove it so know it works. Didn’t come with the battery though
Got it it home and put the new battery on at night and like a dumb s$&@t I reversed polarity and smoked things.
I have replaced the starter solenoid and the alternator relay and replaced an in line fuse that was going to the starter relay. There were a couple wires with disable links that I cut out and wired just to try to get it to fire up.
I get nothing. No lights, doesn’t try to crank at all. No click on the starter at all
I get 12v to the relay but nothing on the other side when we try to start it
what else should I look for?
First time with ford stuff so could be simple thing, don’t know
thanks
Also,
I replaced the horn relay also but what is weird is that when he touches the wheel the horn honks. Not the horn button, the actual wheel. don’t know if that means anything besides it’s a wiring issue on that. Now I know why the horn was unhooked.
i ran it and drove it so know it works. Didn’t come with the battery though
Got it it home and put the new battery on at night and like a dumb s$&@t I reversed polarity and smoked things.
I have replaced the starter solenoid and the alternator relay and replaced an in line fuse that was going to the starter relay. There were a couple wires with disable links that I cut out and wired just to try to get it to fire up.
I get nothing. No lights, doesn’t try to crank at all. No click on the starter at all
I get 12v to the relay but nothing on the other side when we try to start it
what else should I look for?
First time with ford stuff so could be simple thing, don’t know
thanks
Also,
I replaced the horn relay also but what is weird is that when he touches the wheel the horn honks. Not the horn button, the actual wheel. don’t know if that means anything besides it’s a wiring issue on that. Now I know why the horn was unhooked.
Logistics Pro
Joined: Jul 2005
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It sounds like the main fusible link, are you sure you got them all?
Remove the horn pad from the steering wheel (two philips screws in the backs of the 'spokes') and see if the wires are connected. It sounds like something is moving enough to ground out when he touches the wheel,so maybe the steering column ground is bad and the horn pad/switch is stuck on.
Remove the horn pad from the steering wheel (two philips screws in the backs of the 'spokes') and see if the wires are connected. It sounds like something is moving enough to ground out when he touches the wheel,so maybe the steering column ground is bad and the horn pad/switch is stuck on.
Lead Driver
Joined: Jul 2017
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From: San Jose, CA
What meangreen said. Only thing that keeps power from reaching the cabin is the main Black w/yellow wire from the starter relay/solenoid through the firewall. It's got a fusible link too, so that may have been compromised.
On my '79 it runs across the cowl area above the firewall and terminates at a junction block mounted over on the driver's side. Not sure if your '77 has the same layout or not.
Of course, a battery cable can do it too, or a deteriorated main ground point, but since you said you could read voltage at the starter relay's battery side, you're probably good there.
But you can double check that with voltage drop tests I presume, OR by making sure that when you test for 12v at the relay, instead of using the battery terminal as your ground you use some other point on the body..
If you get a reading at the relay using the body as the ground, then most likely your fusible link in the Black w/yellow wire is open/blown.
Paul
On my '79 it runs across the cowl area above the firewall and terminates at a junction block mounted over on the driver's side. Not sure if your '77 has the same layout or not.
Of course, a battery cable can do it too, or a deteriorated main ground point, but since you said you could read voltage at the starter relay's battery side, you're probably good there.
But you can double check that with voltage drop tests I presume, OR by making sure that when you test for 12v at the relay, instead of using the battery terminal as your ground you use some other point on the body..
If you get a reading at the relay using the body as the ground, then most likely your fusible link in the Black w/yellow wire is open/blown.
Paul
Senior User
Joined: Nov 2015
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From: FL & NY
Re: no power
Also check the fuse link between the starter solenoid and alternator - will open circuit when polarity is reversed when jump starting.
Not a good idea to run with fusible links bypassed, can cause a pile of issues if it sees reversed polarity again.
Not a good idea to run with fusible links bypassed, can cause a pile of issues if it sees reversed polarity again.
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Thanks for all the insight. We pulled apart the dash and key switch etc and traced that wire and had no power just like you thought
found the yellow with black by the solenoid and no power
jumped it with power and truck fired right up and ran
so now we know it’s between coming out of the starter solenoid and either before or after the alternator. There are some fusable links in those lines so one of them is the culprit
we are going to get some new automotive wire , a new style fuse box and redo those wires without fusable links and use the block
see any issues with that?
This has had some modifications done to it by the previous owner that I want to redo better.
found the yellow with black by the solenoid and no power
jumped it with power and truck fired right up and ran
so now we know it’s between coming out of the starter solenoid and either before or after the alternator. There are some fusable links in those lines so one of them is the culprit
we are going to get some new automotive wire , a new style fuse box and redo those wires without fusable links and use the block
see any issues with that?
This has had some modifications done to it by the previous owner that I want to redo better.
Lead Driver
Joined: Jul 2017
Posts: 9,600
Likes: 1,174
From: San Jose, CA
You couldn't prove that by me though, and I've used Maxi-Fuse setups to protect the chassis wiring and Mega-Fuses to protect the alternator's battery charging circuit. Both without ever any hint of trouble. But that's more likely to be due to nothing actually ever going wrong, as opposed to there being something inherently disfunctional with the fuse setups.
I usually use 60a Maxi for cabin power, and 175a Mega for protection of the 6ga (or 4ga) charge wire from a 3G alternator.
Good luck.
The good part about fuses is they're much easier to fix on the side of the road or trail.
Paul
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