Truck Electrical Problem!

[Sjorge450R]

Well. My faithful 1987 3.9 4x4 Dakota just became a mess.....

When i was home for Thanksgiving, I was driving it around and it was fine. Drove to work the one morning, when I got out it smelled like something burning (not oil, but actual fire. So i popped the hood and nothing. I figured it was a leaf or something on the exhaust. Any way. Drove home from work (about 6 miles) and I noticed taht my voltage gauge was going down. I thought 'what ever, its just fluctuating cause of the headlights, heater, radio, etc. I go out to dinner that night and when I was on my way home, lost my turn signals, parking lights, radio, dash lights and my headlights were very dim.

BTW, everytime I started my truck since the 'fire' it started fine. There was no sign of stress on the battery.

Anyone would say alternator and so did I. Got a new one, truck died on my dad again, but he was out on the road. I figured at first that the burning smell was the alternator burning up, but now I think something else may have shorted.

Anyone have any insight on what to check out before I scrap this thing and just finance a Trans-Am...lol

[fastredrider44]

It's hard to say for sure, but it sounds to me like you have a dead short in the main harness, probably where it goes though the firewall. Other than that, I can't give you any advice other than older Dodge's are notorious for electrical gremlins. :rolleyes:

[Sjorge450R]

Would that make a burning smell though? I havent had a chance to look over it as I went back to school, but could a relay have burned up?

[eastside 400]

anytime a wire shorts, there will be a burning smell, the smell comes from the melted insulation. Does everything still work or is something inop. right now, a fuse should of blown before a wire would completely short out. If you smelled burning then it should be pretty easy to track down, follow all the harnesses and look for burned up spots

[Sjorge450R]

another thing. My EGR sensor came on when I charged my battery back up????? not sure why. I actually removed the switch from within the dashboard I long time ago so i have no idea why it is showing up.

[eastside 400]

EGR sensor light? are you sure its EGR, and what kind of switch would be in the dash for EGR

[Sjorge450R]

Originally posted by eastside 400
EGR sensor light? are you sure its EGR, and what kind of switch would be in the dash for EGR

100% sure it is the 'Check EGR'. Oh and in the dash. I found this little box style switch that had a 9v battery in it. I know. It sounds fake, but it was there and I took it out and threw it away...lol.

[eastside 400]

how does the truck actually run? if its running bad you might have a clogged EGR, this will stumble the engine severly and that might be enough to dim out everything

[Sjorge450R]

truck runs 100% fine. There isnt one issue besides the battery dying.

would it work if I ran a continuity test on my alternator wires?

[eastside 400]

if you have a multimeter, check the voltage at the alt. with the truck running with the AC and all the other acc. turned on, this will load test everything. let me know what you get. you can connect the meter at the battery, it wont matter.

[Sjorge450R]

So I can test from the battery when the truck is running? I don't see how that would help because I already know that the alternator isn't charging the battery.

[eastside 400]

are you sure that its not? check the voltage at the battery, then check the voltage at the output terminal of the Alt. if you replaced the alt and you still have a problem, then its either the power supply to the alt, or a bad +cable

[Sjorge450R]

isnt there a 'poor mans' alternator test? By which you just remove the negative battery cable from the battery and if the truck runs the alternator is running and if it dies, its not?


Sorry for all the questions. I need to relay this to my dad to try because i am away at college for the next two weeks. And yes, the alternator was replaced. What excatly is the power source for the alt? Is it just a relay or something?

[eastside 400]

i wouldnt suggest disconnecting the -cable, that is the main ground for the truck. do you have a multimeter? the 'power source' all depends on model, i can get you any wire diagram you would need or any tech info, i have access to it, i am a tech fulltime. on all alt. there will be a couple of wires in a harness sometimes only 1 or 2, sometimes more, there is usually a ground and a power source, its a real small wire, it doesnt produce any power but it supplies a small amount to magnetize the alt. in order for it to work. The thing im wondering is that something had to melt if you smelled burning, unless it was just the old alt, but maybe it took something out when it burnt up

[Sjorge450R]

Originally posted by eastside 400
[B but maybe it took something out when it burnt up [/B]


thats what I am thinking. I am probably just going to tell me dad to leave it along until I get home so that he doesnt start messing with stuff and then forget what he does...lol. You know how that works.

Also, my dad really doesnt know how to use a multimeter so we would be stopped in our tracks until I can get home to do it. I will let you know if I need a diagram and I wanna thank you in advance for everything.

[fastredrider44]

The poor man's alternator test usually doesn't work. I've tried it before. The multimeter will be easy to check voltage, and you have to do it with the truck running or else it won't help. I would say you can take it in to Auto Zone or where ever, but 9 times out of ten, they don't know what they're doing and will try to sell you a battery or alternator when you don't need one. And a check EGR light? I'm not calling you a liar, but are you sure? Most of the time a clogged EGR will trip the Check Engine light or Service Engine Soon light and throw a code. However I do realize that your trukc is an OBD 1 computer, so who knows...

[Sjorge450R]

Originally posted by fastredrider44
The poor man's alternator test usually doesn't work. I've tried it before. The multimeter will be easy to check voltage, and you have to do it with the truck running or else it won't help. I would say you can take it in to Auto Zone or where ever, but 9 times out of ten, they don't know what they're doing and will try to sell you a battery or alternator when you don't need one. And a check EGR light? I'm not calling you a liar, but are you sure? Most of the time a clogged EGR will trip the Check Engine light or Service Engine Soon light and throw a code. However I do realize that your trukc is an OBD 1 computer, so who knows...

hahaha, nah not lying here and I even talked to my dad earlier and he said taht it is the check EGR....maybe its trying to say check engine cause I dont think i have a check engine light. Either way, its on and I have no idea why, because it came on after I took my battery out to charge it. (took it out to charge because I needed to change my front turn signal bulb and its easier with teh battery out anyway.


my did how ever stop and talk to our mechanic and he said that there is something called a fuse link or link fuse. Apparently it should be inline for the alternator or positive battery terminal. Could any one give me any info on that?

[fastredrider44]

If there is an inline fuse, it would be on the hot wire leaving the alternator, however I have not ever seen one on a truck, but I can't say that I've ever looked under the hood of a dakota. It would probably be a big blade style, or a long skinny fuse. Either way, it shouldn't be hard to find if there is one. The only reason it would have blown if there was a TREMENDOUS load on the alternator. I've heard of loads that big occurring from a dead short which is what I suspect you have somewhere (Why its not tripping a different fuse I don't know) or when you jump a vehicle and remove the jumper cables immediately, and the alternator is working overtime to charge a dead battery that is bad to begin with.

[eastside 400]

that is not the kind of fuse that is inline from factory, older vehicles used fusible links, which were parts of a normal wire that were made from a smaller diameter copper wire and is designed to burn apart at whatever amperage its designed, its not a actual fuse, you should be able to tell where it is in the wire, they are usually marked.

You are also using the term load a little loosely, a dead short is not a high load, it is actually no load, allowing the amperage in that circuit to spike. consider amperage water in a hose, the more restriction=the less amperage and if it has a free path to ground i.e no load no restriction then the amperage spikes and that is when a fuse blows

[Sjorge450R]

that fusible link sounds like it could be the problem. Hopefully my dad sees something when he checks it out. how to I replace this fusible link? Can i buy this special wire somewhere?

[eastside 400]

you should be able to buy a piece of fusible link, im not totally sure, if not, just buy an inline fuse kit in the same amperage, the easy way to check the fusible link without a multimeter is to pull on that section of wire, if it stretches out then it has blown

[Sjorge450R]

problem fixed! My dad got frustrated with my truck so he took it to our mechanic. After a little bit of testing he found out that one of the regulators on the firewall shorted out.... Ended up costing $50 so its not that big of deal.....

I just would like to thank everyone on here for all of the help.

Steve

[fastredrider44]

50 bucks spent is better than hours on end not knowing what you are looking for.

[Sjorge450R]

i know right. I guess thats what my dad thought too. he called me yesterday and was like, I am taking your truck in, I cant find anything. Considering that it was only $50, I guess the mech took about 30min and the part was about $25....lol. That sounds about right.