Bad Alternator?

[WHRoeSr]

68 Bronco. Just got it out of the body/paint shop after 1.5 years. Bugs are popping up now.

Appeared to have a bad battery (had to charge up a couple times) when leaving the paint shop so replaced it with new. This was 4 days ago. Was starting and running fine until last night. Cold starts not a problem - fired right up every time with the new battery. Last night while driving, my aftermarket radio was powering on and off. And the newer H4 LED headlights seemed to be on low light output but it had been quite a while since I had driven at night so I wasn't sure about that.

This morning on a cold start, it reluctantly fired up on first crank. Didn't think much of it. I drove it 2 miles down the road to a gas station to fill up. After it was gassed up, tried to start, and nothing. Would not turn over. A good samaritan stopped and jumped me. Took several minutes to charge up the battery enough to start it. Drove it 2 miles back to my garage. Shut off the engine and immediately tried to start it again. It started, barely. Shut it off and tried once more. And nothing...wouldn't even turn over.

Alternator is junk?

Thought maybe something was left on and was draining battery juice overnight, but now thinking that the radio powering in and out while driving last night is saying otherwise.

I'm a far cry from being a mechanic. Have not tested anything yet. Thought you all in here could give me some quick pointers!

Thanks in advance!

-Hank

 

[Beau Nugget]

With the key off, you could take one of the battery cables off. When you touch that battery cable back to the battery post, you just removed it from, look to see if there’s any minor sparking, that would indicates that there’s a draw of electricity on the battery even when the truck is off. I’m not talking about a large arc of electricity. Just Very small subtle sparks If there is no draw of electricity from the battery, there will be no response when touching the battery cable back to the battery post— which is what you want.

Otherwise, a bad alternator sounds like a likely reason for your problems

 

[904Bronco]

Fully charge the Batt
Alt belt tight? Terminals on Batt clean and tight?
Turn the key to run, does the field wire (Green/red stripe) have Battery voltage.
Is there batt voltage at the Batt terminal on the Alt?
Does the voltage at the Batt rise once you start the rig up?
Amp gauge show charge, assuming you still have that...

 

[m_m70]

I would start with getting the battery fully charged. A two mile drive is nowhere near enough to charge your battery. But that doesn't explain why it's dead in the first place.

How old and clean are your cables??

get yourself a voltmeter or better yet a multimeter and start checking for voltage. With your volt meter, you should be able to see if your alt is charging and I would start there.

Lots of stuff can cause what your experiencing. Usually, pretty easy to fix.

 

[gnpenning]

As mentioned you are going to need a multi meter to isolate the problem.

You just got it from the paint shop, was it painted under the hood?? Check.ground connections.

You can check your parts store and see if they have a alternator tester and battery tester. Be aware that the battery has to been charged or attempted to first.

Do not start throwing parts at it until tested and proven bad.

 

[m_m70]

Do not start throwing parts at it until tested and proven bad.

THIS^^^^

You just got it from the paint shop, was it painted under the hood?? Check.
ground connections.

Soooo important. May explain your stereo issues, dim lights, no charge etc............

 

[DirtDonk]

Did the paint job include a rewire, or just a paint leaving everything together?
If it’s original, you should be watching your ammeter. Hopefully it’s still working after 50 years, but when they worked, they worked very well.
If it’s been replaced the voltmeter you should be watching that as well.
What do the gauges read? Both engine on, and engine off?

Keep a voltmeter handy. Both for those tests described above, and for any checks you may need until you get this resolved.
A voltmeter is any Bronco owners friend.

 

[WHRoeSr]

I would start with getting the battery fully charged. A two mile drive is nowhere near enough to charge your battery. But that doesn't explain why it's dead in the first place.

How old and clean are your cables??

get yourself a voltmeter or better yet a multimeter and start checking for voltage. With your volt meter, you should be able to see if your alt is charging and I would start there.

Lots of stuff can cause what your experiencing. Usually, pretty easy to fix.

Battery was brand new & fully charged a few days ago. Will clean all cables and check voltages!

 

[WHRoeSr]

Did the paint job include a rewire, or just a paint leaving everything together?
If it’s original, you should be watching your ammeter. Hopefully it’s still working after 50 years, but when they worked, they worked very well.
If it’s been replaced the voltmeter you should be watching that as well.
What do the gauges read? Both engine on, and engine off?

Keep a voltmeter handy. Both for those tests described above, and for any checks you may need until you get this resolved.
A voltmeter is any Bronco owners friend.

No rewire, just a paint job and lots of body work including new some new quarters & fenders (from WH ) and a new hood! Ammeter not functioning. Will put a voltmeter on it!!

 

[WHRoeSr]

THIS^^^^



Soooo important. May explain your stereo issues, dim lights, no charge etc............

Yes painted under the hood in fact a new hood was installed. Will check the grounds.

 

[NGABronco]

Does your rig have a voltage regulator???

 

[WHRoeSr]

Does your rig have a voltage regulator???

Yes but it does not function. On my list!

Will be testing with a voltmeter thanks to the helpful feedback from these replies.

R

 

[Oldtimer]

Once voltage regulator is working, charging current has a long path from alternator to battery.
All the connectors need to be clean and tight.
If ammeter is not working, the Black/Yellow stripe wire may not be going thru loop on back of ammeter.

The two bulkhead connectors are in firewall, near driver side valve cover.

The bullet connector is behind speedometer, near ammeter.

 

[86Horn_EB_77]

I know this thread is a few months old now, but I'm struggling to get my old original Gen 1 Alternator/Voltage regulator to work on a 72 that I'm working on for a neighbor...
New AC Delco alternator and new voltage regulator - and I can't get any voltage above "nominal" (12.4 to 12.6V) at the battery. I can make the alternator charge to 17V at the B+ terminal if I ram rod the field excitation with a jumper wire from the battery +, so I know the alternator is good. Although 16-17V at the B+ terminal translates into only about 14.5 volts at the battery - so there's some significant voltage drop in the wiring. I know there's a tortured path from Alt B+ to the dash ammeter and back to the starter relay but... I found and unplugged/plugged the bullet connection behind the speedo. This truck doesn't seem to have those bulkhead connections shown above - so maybe that's a 66-68 only thing? Tried a couple of regulators - old one & new one - same result - I get about 12.0V at the alt B+ with regulator plugged in and truck wiring connected to B+

The wiring in this 72 is VERY original (read that as old and crispy) - but I do seem to have all the right voltages at the voltage regulator connector - full batt voltage at one of the yellow wires all the time, and maybe 0.5V less than batt at the other yellow with key on. The orange field excitation wire ohms out between the connector and the alternator. I cleaned up some of the under dash and starter relay connections - just in time for the starter relay to die - so I can't test it until amazon delivers a new relay.

Besides going under the dash and checking every connection in the big black w/yellow feed from the alt, and the black & Black & red feeds back to the relay/battery - is there anything else I can do?

 

[DirtDonk]

The firewall connectors were only present until the 70 model year. For 71 and they are all like yours.
Bundles of harness passing through grommets in the firewall.

I’m glad you checked the bullet connector and found it clean. And hopefully it’s tight too.
There should not be that much loss between it and the battery, of course. As you said. Not sure where else the drop could be.
There are a couple of factory spilces hooked into that black wire, but as far as I know, there are no breaks other than that connector at the ammeter.

A question though. It sounds like everything else is working? You can start the engine by turning the key?
And this is a factory original harness? Not a replacement?

When the engine is running, but before you arefull-fielding it, is the BAT output of the alternator reading 14 V or more?

 

[gnpenning]

When you tried the different regulator, was it bolted down with a clean ground path or did you use a jumper wire for the ground?

 

[86Horn_EB_77]

A question though. It sounds like everything else is working? You can start the engine by turning the key?
And this is a factory original harness? Not a replacement?

When the engine is running, but before you arefull-fielding it, is the BAT output of the alternator reading 14 V or more?

Hey DirtDonk - glad to see WH/Tech support is online even on New Years Eve!

With a good starter relay... it was cranking and starting, until it wasn't... putting on a new relay today. Exterior lights work but dash lights don't There's all kind of old ripped out stereo, winch and CB radio wiring under the dash - I'm trying to ignore it but I may have to dive in.... it certainly is the original 1972 harness - with all it's crispy goodness. With everything plugged in as it should be - I was getting 11.9 V at the B+ terminal. And it wouldn't do much better if I full fielded it with the Black/yellow wire connected to B+. But, if I disconnected the truck from B+ and full fielded it - then I would get 16-17 volts at B+. I think that tells me the truck is loading the alternator down - and not enough voltage is making it back to the battery.

And yes - I grounded the voltage regulator when I tested the other one - made no difference in Batt voltage.

I am constantly reminded that 12V doesn't tolerate dirty connections very well - I will have to clean the inner fender voltage regulator grounds now that I think about it...

In general - the connections at the starter relay also weren't the cleanest - so I'm hoping a new relay and wiring terminal cleaning will solve my issues. I think the voltage drop got better after I worked on the bullet connector, but then the starter relay died... so... hopefully better luck today... Truck obviously needs a complete rewire - but this is the classic - "just get it running for my 75 yr old neighbor" kind of deal... It's a pretty neat old half cab with a bunch of Stroppe Aftermarket mods on it - he needs to be tooling around in it - and I need it out of my driveway !!!

 

[4xfun]

The negative battery cable may be going bad. It will corrode from the inside. if it is real bad shape, you can hear a crunchy sound when you bend it. Use your voltmeter and check the resistance of the cable.

 

[DirtDonk]

Just for giggles, test the 4-position connector at the voltage regulator.
Pull it off of the regulator, then test voltages at each of the three wire locations.
There should be nothing on the orange field wire.
There should be nothing on the Green w/red wire with the key OFF. But full voltage with the key ON.
There should be full battery voltage on the yellow wire. If not, it should not have more than one or two tenths of a volt less.

 

[DirtDonk]

Got some pictures of the engine compartment? Specially, around the starter relay and alternator?