1980 4x4 20R Charge Light, blown engine fuse, alternator not charging (1 Viewer)

[msahr]

The thread title says it all. CHG light on the dash all the time. Well it does flicker when driving. Fully charged battery at 12.7 volts, start engine, voltmeter across the battery terminals shows the same voltage when revving up the engine. My fancy Sears battery charger says "CHK" with red light on "Alternator Test". ENG fuse blows as soon as the engine starts. I don't see any shorts but obviously I'm missing something. Any insight on what to look for? Thanks

 

[ferg]

Possible bad alternator. How many fuses have you been through?

 

[msahr]

3 so far. First one was already blown, second one blew, so I put another one in and watched the fuse when I started the engine. Fuse blew right as the engine caught. I found a package of 15 amp fuses in the glovebox from the previous owner.

 

[clx16]

If you've not tried it yet, scotty kilmer has two videos i think on youtube for chasing electrical problems/shorts. Just need a multimeter so worth the checking before you take a trip to get the alternator tested and or start replacing things.

 

[msahr]

If you've not tried it yet, scotty kilmer has two videos i think on youtube for chasing electrical problems/shorts. Just need a multimeter so worth the checking before you take a trip to get the alternator tested and or start replacing things.

Thanks I'll look it up.

 

[pappy]

What else is on that fuse?

 

[cruiserdan]

It could be the charge lamp relay. 27790-41010.

 

[clx16]

@cruiserdan i am not familiar with charge lamp relay but is it the same setup as the 60 series? Charge lamp relay = violence :p

 

[cruiserdan]

I spent my automotive career behind the parts counter so I couldn't say if the do exactly the same thing but I wouldn't be surprised. I do remember that when the relay failed all kinds of wierd stuff happened. All I ever did however, was hand them out.

 

[msahr]

It could be the charge lamp relay. 27790-41010.

View attachment 2506540

Thanks. Nothing to do tomorrow so I'll track it down.

 

[pappy]

I spent my automotive career behind the parts counter so I couldn't say if the do exactly the same thing but I wouldn't be surprised. I do remember that when the relay failed all kinds of wierd stuff happened. All I ever did however, was hand them out.

Gosh, I feel so left out. Should I give Sean a call?

 

[msahr]

I swapped out the regulator from my 83 and like magic, CHG light went out after starting and the fuse didn't blow. Already ordered a new one. However, still not sure if it's charging. No movement on the amp gauge.

 

[pappy]

However, still not sure if it's charging. No movement on the amp gauge.

That's easy. Start truck. Take volt meter to battery. It will say ~14.3 if it's charging.

 

[msahr]

Yup. And it isn't which leads me to believe it's not charging. Stuck around 12.4V. Man I LOVE tracking down mystery electrical. Especially when there's been creative rewiring.