Last two days noticed the CD player cutting out for about 10 sec at a time...though it was scratched CD. Unit stayed on (lighted) though.

This morning smoke coming from under dash. Shut it down, grabbed the extingisher and waited to see flames. Smoke cleared and no flames.

Took radio out, looked in hole in dash: a red (?) wire coming off the ignition/key switch was fried but still had strands of copper intact. It led to a bunch of wires in a rubber connical thing, and one of the wires coming off that (red?) was completely fried off.

So I'm guessing:

1. Need new ignition switch?
2. Need to toss the old stereo?
3. Any other ideas? (Sorry, no pics at this time.)

Thanks! Dan

 

It's going to be tough to give advice without pictures.

 

In the future when there is smoke in the cab, 1. STOP truck 2. Put in Park 3. Key off
4. Go for the + battery connector under the hood. 1,2,3 are done usually in rapid succession, lol.

At least you had a fire ext, so a little pat on the back. And I would always try to wire stuff thru the key to be able to kill the power with a flick of the switch.

Yes to the probably fried stereo, so ditch it and find the culprit wire if you can. You might get away with the same key switch assembly, pull the switch assembly (out side dash 3 slot ring comes off) lefty loosie... then push switch body into dash and remove.

Disconnect and insp for melting in the big 9 pin cannon plug connector behind it. Then insp the connector and all the wiring under the dash associated with that bundle.

You need to find the short or what caused the original issue, so you do not burn up all your repair work. With the key on and power going maybe places you do not want or need at the time you might have fried a few things? Orange "Fusible link" by starter solenoid?

You will probably have to strip some cover tape and look close for melted wires and ck all your fuses. Hopefully it was just a stereo power wire or the stereo itself?

Once all that is done I would repair and reassemble as needed, and connect batt, ck things, key on (don't start truck yet) and recheck things one at a time like wipers, heater switch, head lights,turn signal ect....

All the off, start truck ck things like dash volt meter and batt reading (12 to 14 amps right?) while idling. Then ck all power stuff again..... you might of burnt up the voltage regulator (4 wire blade connector silver box by starter solenoid) and or the alternator.

Let us know what you find......

 

Thanks very much for the detailed suggestions and help--wow, I was hoping for some input but you really gave me a lot to think about and check. As usual you are helpful! Reps coming your way. (Edit: apparently I've given you reps recently and it won't let me do it again until I spread some more around--someone give him some for me!)

Yes, I even have a battery disconnect sitting in the garage that was to go in the 67 Mustang I used to own (one evening one of the switches--maybe blower motor--was REAL hot to the touch and I knew that wasn't a good sign--but ended up selling the car before long.) I need to put it in the truck.

It's going to be several days before I get to it. I'm leaving town for a while and so it's going to have to sit...outside the garage and with the battery disconnected.

Thanks again and I'll report back when I get digging into things.

Dan

 

I got him for ya.

 

First and foremost:

1) You need to determine what wire fried (as in what was its purpose).
2) With that information, you need to determine why it fried.
3) Lastly, you need to determine what else that wire was bundled with. The reason is that wiring harnesses are often tightly loomed, and when one smokes like this, it often melts the insulation off everything it touches. Do not apply power to any part of the truck until you've completely disassembled and inspected every path that this wire touched.

Until you answer the first two questions, you can't determine whether or not the CD player had anything to do with it - they could be unrelated.

Please post as many picture as you can of the back of the ignition switch and the suspect wire.

 

Here are some pics, all taken through the dash where the radio was. Explanations in each picture.

Looks like a bunch of wires going back to the column (pic 7, last one, I think) show a few with some degree of being burnt/fried. But the worst ones are in the first pics.

 

Some more pics...

 

Goodness grief! Sorry to say, but that wiring harness is toast IMO. At the very least, you'll need to pull the dash forward and remove the entire harness, unloom, and inspect. I've rebuilt one by hand before and it's not a pretty job.

Looks like one of the hot-in-RUN circuits fused out completely. It takes a dead short to ground to smoke off insulation like that.

Hot-in-RUN comes from the ignition switch and branches off to several places: GREEN with a RED stripe to go out to the voltage regulator, RED with a GREEN stripe to go out to the coil, and RED with a YELLOW stripe to power some of the items in the instrument cluster. Looks like the entire path from the key to the junction point is toast, which means one of the loads downstream shorted to ground completely.

My guess is something on the RED with YELLOW circuit went based on where the break is - what year is this? Is this a '79? I can try to guess from there - some things are fused and some aren't.

Your CD player is tied into the hot-at-all-times cigar lighter, which is on a separate circuit and does not go through the key at all. Does your CD player also take a switched signal from the key? If so, where did you tie that? Those signals usually don't draw much current unless something goes completey wrong - at this point I'm not convinced your CD player had anything to do with it yet, but need more info first.

Also, do I see some wire nuts in one of those pictures?

 

70 bronco TX, listen up to ol FMC 400, if he was not so far in Tx I would have him come talk me thru fixing all my wiring issues, he is really knowledgeable on this elec stuff.

So take your time and get it right the first time to avoid this issue again, and get to repairing it and let know how it goes, WE (some with a little exp, and some with tons) are here to help.

 

Thanks for the kind words; I tried to rep you but it says I did it too recently.

 

I got you though....rep sent, and by chance do you ever get back up Missouri way? I could use some under the hood elec sys maint/class from you for at least a few hours lol.

And I would jump at a "Ford truck elec/multimeter 101" with you.

 

FMC400, thanks for the perspective. Yeah, probably a new harness...not looking forward to that.

The truck actually started and I drove it to my mechanic to take a look at. It's a 75 F250.

Not sure if I'll attempt the fix myself or see what they can do first. The wire nuts are all related to the stereo (speakers). The stereo was wired in by Best Buy about three years ago (all of this isn't sounding good, I know.) I don't know if the stereo takes a switched signal from the key.

 

smart..........

 

This resistor wire was only available by itself, it did not come with the wiring harness. There are two possibles.

D1AZ-12250-A .. Resistor Wire-Ignition Coil (Motorcraft DY-84-A).

60" long / Color coded RED with GREEN stripes / 1.30-1.40 ohms resistance / #16 gauge wire.
-------------------------------------------------------------------------------------------
D7AZ-12250-A .. Resistor Wire-Ignition Coil (Motorcraft DY-213).

60" long / Color coded RED / 1.30-1.40 ohms resistance / #16 gauge wire.