Alternator fried something...

[Cbassslayer]

NEWBIE:

1971 FJ40 LC with a SBC 350 conversion was running decent, until.... So I though about adding some electrical stuff to my rig. New Battery 12.8 (good), Alternator output a measly 13.1 (bad).

So I decided to buy one of these fancy chrome "powermaster" alternators (summit PWM-17294) putting out 100 amps. So I hooked it up and viola, 14.6 (+/-), rig was running smoother. Also, a few months back I took the distributor load off the ignition switch and routed it to a relay to the new MSI distributor. Getting great voltage to the new MSI distributor. Switch was getting real hot.

So after installing the new alternator, the rig ran great for a few minutes in the garage, then....poof, it just died. Not getting any current to the distributor (via spark plug check). And there was a distinctive smell like I fried something.

On the old alternator there was one wire looped from the Bat post to the # 1 terminal, and another going into the wire loom from the # 2 terminal, and a third (thicker) red one going into the loom. I know in the photo's the #1 and #2 are reversed (just quickly put them on for the pics).

Can someone please help me figure out what to do. I am not the best electrical guy, but I do have a pay pal account . I pulled the ignition switch and nothing looked melted. I am assuming I fried the VR but I'm not even sure where it's at. There is a little square thing right below the heater box.

 

[Cbassslayer]

I checked all the fuses and they are good.

 

[78fj40mg]

That alternator has an internal voltage regulator. Have you been able to the determine the origin of the burning wire smell?

Alternator data
https://www.summitracing.com/parts/pwm-17294

 

[78fj40mg]

You may want to check the fusible link which is connected to the battery, because if you have a short in the system the fusible link will melt before anything else.

It looks like this

 

[78fj40mg]

This is where it connects to the battery the white wire with the yellow crimp connector connecting to the battery red wire

 

[78fj40mg]

Believe it or not but your battery is still connected, move the negative cable away from the neg. batt. pole

 

[Cbassslayer]

That alternator has an internal voltage regulator. Have you been able to the determine the origin of the burning wire smell?

Alternator data
https://www.summitracing.com/parts/pwm-17294

I have located wires from the starter and wires dealing with engine power and they all look dated with multiple krimped connectors, etc). I am going to fix all the connections and put back together, today.

 

[Cbassslayer]

That alternator has an internal voltage regulator. Have you been able to the determine the origin of the burning wire smell?

Alternator data
https://www.summitracing.com/parts/pwm-17294

You may want to check the fusible link which is connected to the battery, because if you have a short in the system the fusible link will melt before anything else.

It looks like this

I don't think I have a fusible link connected tot he battery. I used that yellow wire to send power through the relay to the dist once activated by the ignition.

 

[Cbassslayer]

This is where it connects to the battery the white wire with the yellow crimp connector connecting to the battery red wire

I used that yellow wire to send power through the relay to the dist once activated by the ignition.

 

[78fj40mg]

Without a fusible link bad things can happen, however, lets continue with the trouble shooting, have you found the toasted wire?
You will need a VOM to check for a compromised wire.

You might want to also check that relay, see if its fried.

 

[78fj40mg]

Do you have a pic of the alternator connections?

 

[Cbassslayer]

Believe it or not but your battery is still connected, move the negative cable away from the neg. batt. pole

It is completely removed.

 

[Cbassslayer]

Without a fusible link bad things can happen, however, lets continue with the trouble shooting, have you found the toasted wire?
You will need a VOM to check for a compromised wire.

You might want to also check that relay, see if its fried.

I put on a duplicate repay and it didn't fix, nor did it fry/smell. Here are some pics from the wires going from the battery to the starter.

 

[Cbassslayer]

I put on a duplicate repay and it didn't fix, nor did it fry/smell. Here are some pics from the wires going from the battery to the starter.

View attachment 1291984

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View attachment 1291988

I am going to sears real quick to get some wire and stuff. Be back in about an hour. I am going to fix those wires and harnesses. Then I need to put in A BATTERY FUSE. I will see what they have at sears.

 

[Cbassslayer]

Do you have a pic of the alternator connections?

If I am not mistaken, BAT jumper always goes to # 2. It was working beautifully at 14.7 VDC. Motor was purring.

 

[Cbassslayer]

I put on a duplicate repay and it didn't fix, nor did it fry/smell. Here are some pics from the wires going from the battery to the starter.

View attachment 1291984

View attachment 1291985

View attachment 1291986

View attachment 1291988

That starter wire right there looks like it could be the culprit.

 

[Cbassslayer]

That starter wire right there looks like it could be the culprit.

Off to get new wire and connectors.

 

[78fj40mg]

Here's a simple GM wiring diagram

 

[Coolerman]

First: Early 71's 9/70 to 9/71) do NOT come form the factory with fusible links. Fusible links started with the 72 model year (10/71 and later). You must have a later 71 as the early 71's did not have a large white wire going to the battery, instead it connected to the starter B+ stud instead. However you sort of do have a fusible link in the form of that smaller red wire off the positive battery terminal you connected the much larger white wire to. It's not ideal, as it appear to only be twice as small where it should be 4 times as small, but better than nothing at all. Once you get this sorted out, if you want a fusible link send me a PM. I make a retro fit kit for the early 71 and a OEM version for the 10/71 and later.

Second: Did your old alternator have an external voltage regulator? Can you find, and post, the model # of the old alternator or take a pic of the back of it? With that info we can tell you if you need a voltage regulator. I would bet that the regulator was bypassed or removed when the V8 was originally installed.

BTW the OEM voltage regulator location is under the hood, on the drivers side firewall, above the dimmer switch. Small black box. It should have three wires going to it: White/Green, White/Red and White/Black

Third: If your Amp Meter used to work, but now does not, your 100 amp alternator may have fried that. If it's fried, your electrical system will be dead. To check this: Disconnect the battery!!! Pull the gauge cluster, locate the amp meter wires (large White/Blue and large White wires) take the White/Blue wire off it's terminal post and place it on top of the white wire right next to it and tighten it down. This basically bypasses the amp meter. See if the truck now acts correct. If it does then you can leave it like that but of course your amp meter will not function.

Another thing: I noticed that the battery negative post is going to the alternator bracket. You also need a same gauge ground wire going from there to the FRAME of the truck.

 

[Cbassslayer]

So it turns out that the control module in the HEI MSD distributor was fried. Before I replaced, I went through all of the wires and did a bunch of replacements. Still chasing new wiring, but it fired right up.