Battery charging issue

[Sampsont]

I’ve got a new battery and alternator installed in my 77 bronco and when testing the system with a volt meter without the truck running I get a reading of 12.46. With the truck running it drops to 12.2 and stays there and with headlights on it drops further to 12.03. If everything’s working properly shouldn’t the volt meter jump up to the mid to upper 13s with the truck running?

 

[blubuckaroo]

I’ve got a new battery and alternator installed in my 77 bronco and when testing the system with a volt meter without the truck running I get a reading of 12.46. With the truck running it drops to 12.2 and stays there and with headlights on it drops further to 12.03. If everything’s working properly shouldn’t the volt meter jump up to the mid to upper 13s with the truck running?

Yes, you should have 14 volts or more.
Try full-fielding the alternator to find out whether it's the alternator or regulator at fault.
All you've got to do is supply full battery voltage to the "F" terminal of the alternator or regulator, and start it up. Then check the output voltage.

 

[DirtDonk]

New alternator. Could be the new part of course (it often is these days) but it could also be the way you hooked it back up.
Were you careful to attach the same wires to the same posts? Orange wire to the FLD post, White w/black wire to the STA post, large Black wire to the BAT post, and the metal ring sticking out of the rubber strain-relief to the GRD post (or most convenient case bolt) location?

Stock wiring? Stock alternator?
Did you connect anything, or mess with any of the wires while the battery was still connected? If so you could have fried the regulator if it wasn't grounded, or blown the fusible link (at the end of the Black wire under the battery cable on the starter relay/solenoid.
Either of those mishaps would keep your charging system from working.
Then again, maybe the new one was just bad right out of the box.

Good luck.

Paul

 

[Sampsont]

Thanks guys for your input. Paul you helped me with my hub/rotor replacement. I’ll share a bit more context to this existing charging issue. It is stock wiring wiring, alternator, etc. The kid I purchased the bronco from mixed up the positive/negative cables to the battery so when he connected them it caused this issue...some wires fried. I’ve looked all over for the complete alternator wiring harness from regulator to the alternator and can find nothing...only a pigtail that plugs into the regulator. There’s complete harnesses readily available for 71-73 broncos, but like I said I’ve located nothing for a 77 bronco. Because I could not locate something I ordered the alternator wiring harness for a 73 bronco because the wire colors and configuration look identical to OEM and it plugs right into the regulator and I have the correct wires going to the back of the alternator. So Paul to your point I believe this is a wiring related issue...either from the previous owner mishap or me trying to rig it back together with the 73 harness. You mention the fusible link which I’ll have to take a look at. And it wouldn’t hurt for me to buy a new regulator because maybe it did get fried.

 

[DirtDonk]

It's very possible the regulator got fried at the same time. But trying the "full-fielding" trick that buckaroo mentioned would be a proof of concept and may save you some trouble.

You can actually do it with the engine running and a small jumper wire.
Disconnect the 4-position connector at the regulator and connect the jumper between the Yellow "A" wire and the Orange "F" wire.
If the rest of the system is still intact and working, you should hear your engine strain from the load of the alternator at full output. The belt might even hiss or squeal.
But either way, you should see your battery voltage jump from it's 12-point-whatever to a higher reading of 15v, then maybe 16v, and if left long enough to 17v and above.
This is why you only do this long enough to test. Don't let it charge at full chat for more than a few moments. Unlike Johnny-5, batteries don't like that much input.

If it does not do these things, it's still possible that you have a bad regulator, but it's a sure bet you have other issues still as well.

Paul

 

[Sampsont]

I’ll give the full fielding a try. Never done it before so thanks for the added detail on how to do it!

 

[Broncobowsher]

A simple check is to test for voltage at the Field terminal while running as well. No voltage, regulator or wiring is the problem. If you have pretty much battery voltage at the Field terminal the alternator is dead.
If you have a couple of volts, it is probably a bad regulator that isn't setting the right target voltage, this should get a full field test.

NEVER unplug or plug in a voltage regulator with the engine running or even with the key on. Along the same lines the voltage regulator MUST be bolted down with a good ground. If either is not adhered to the regulator will fail in about 1 millisecond.

 

[DirtDonk]

At least on GM regulators the recommended test had you disconnect the regulator when the engine was running.
Different manufacturers, maybe different designs that handled it better, but I don't believe I've ever tested the theory with either. I'm just too timid and always try to give my electronics a fighting chance at surviving my messing around.

Paul

 

[DirtDonk]

I’ll give the full fielding a try. Never done it before so thanks for the added detail on how to do it!

No problem. Pretty straightforward, but I've got it even easier since I bought a tool about 40 years ago that takes care of all that. One side is patterned for Ford, the other for GM, and you just plug it into the connector and there's your jumper. Pretty cool.
Luckily I've only had to use it once, but you can't have too many hardly-used tools. Right?%)

I should create my own loaner program!

Paul

 

[Sampsont]

Okay Broncobowsher I’ll try the simple test you suggest. When testing for voltage at the Field terminal I’m using the red lead from the volt meter and attaching to the Field Terminal correct? Where does the black lead from the volt meter go? To a ground point so the block of the engine?

 

[Broncobowsher]

Black lead goes on ground. Being as close to the battery as you are, that is where I go to.

Tip: Once you have the meter ground connected, touch the positive post on the battery. You should get a reading of battery voltage. What you are really testing is that you have the ground connected cleanly. If the ground on the meter isn't good enough to get a good reading you are going to have a lot of bad readings and things will be even more confusing. Another thing I will do is if I get a no voltage reading where I should have voltage, test another known positive (battery post, alternator output post) just to make sure I didn't pull the ground off.

If you can't reach the negative terminal on the battery, any other ground spot on the engine will do just fine. Just check that you have a clean ground.

 

[Sampsont]

Charging issue is FIXED!! The field test show zero volt meter reading. I also realized I didn’t have the metal ring sticking out of the rubber strain relief grounded! So grounded this and tried field test again and volt meter read .02 so Broncobowsher per your thread my voltage regulator was probably the problem. I replaced it just now and charging system is reading 14.4 with engine running!! Sweet!!
Another question for you guys - I have a stock hood with stock air cleaner and when I remove the stock air cleaner the engine runs noticeably better. I have a new air filter too. It tells me the stock air cleaner is so restrictive so curious to know what after market air cleaner will fit under the stock hood? Everything for sale on the bronco websites has a warning associated to the air cleaner that it may not fit under stock hood. Any suggestions other than cutting the hood and installing hood scoop?
Thanks again for your help in solving the charging issue!!!

 

[Broncobowsher]

The stock air filter should be a good one. I know a guy running one on a 383 stroker. In stock form it has a duct to the grill so it is a true cold air intake unlike an open element filter pulling hot air from under the hood.

There is a reason why Ford made the air filter the way they did, there isn't much room under the hood.

There will be a sound difference if you don't have it. There is a lot of intake noise that the air filter muffles out. re you just hearing more sound making you thing it is running better? It is possible that the heat riser valve is stuck. That could make it run worse, but that would be just fix the valve and keep the cold air intake.

 

[Sampsont]

Sounds good Broncobowsher. I do like that it has stock cold air intake. Someone at some point in the ownership of this bronco installed an Edelbrock aluminum intake with Carter carb. Not sure if the Carter carb is original though? I’ve been reading up on the 383 stroker and have been told it’s a pretty good upgrade. Also thinking fuel injection and see that CJ Pony has a setup to include intake that bolts on to existing 302.

 

[Broncobowsher]

Carter is not stock. The Edelbrock is almost guaranteed taller than stock. Also worth checking that the air cleaner isn't binding on the choke linkage or anything else.