Hissing battery……

[Billw69]

So I just got home from a short drive in my B1. After I parked it I lifted the hood to disconnect the battery and immediately noticed the battery was hissing? It’s a new battery and I’m not sure what would cause this? The regulator and alternator are both under two years old. I had no unusual indications on the ammeter, which isn’t saying much as it barely moves under normal conditions.

Was planning on driving it to SMN this weekend but now I’m not sure I should drive it at all, since the last thing I want is an exploding battery.
Any and all suggestions welcome.
Thanks, Bill

 

[Sheriff41]

Is it hissing from the caps? It may just not be sealed well. Either way, I'd return it and have it replaced. You don't want to have it causing under hood corrosion.

 

[Billw69]

Thanks Chuck, and yes it is hissing from the caps. My first thought was what you said, take it back, avoid the corrosion issue and change to an Optima and be done with the corrosion threat.
As I researched this some more and had my son measure the voltage on the battery while the engine was running. Static voltage 12.7, engine running battery voltage was 17.6V…..WOWSER….!!! Guess i now know why the battery was hissing.

In the morning I’m going to start with cleaning the engine ground connection at the firewall and the engine as well as the negative battery cable to the engine point. Hopefully I see some improvement.

Thanks again Chuck

 

[Bentworker]

Sounds like the voltage regulator isn’t living up to it’s name.

 

[Billw69]

That will be the first purchase for troubleshooting this issue. Last year I bought a “correct” looking VR from one of the well known vendors, that from the outside looked original but on the inside it was upgraded to modern electronics.

 

[Don C]

Get a Motorcraft GR540B electronic regulator,
https://www.npdlink.com/product/voltage-regulator-alternator/100810/150190

or an original replacement style from NAPA, ECH VR440.
https://www.napaonline.com/en/p/ECHVR440

Another electronic replacement is the Standard Motor Product VR166 https://www.rockauto.com/en/moreinf...XzeIlrrT7yhsshltCUDofntISG8ZRPcfeAlsttHWBgDox

If you want it to look original swap the cover to the old style cover.

 

[midlife]

A hissing battery should only be used in Cobras.

 

[Billw69]

 

[Billw69]

Update; purchased and installed a new VR……. No change… still putting out 18.4v.
I’m told now I should get a new alternator.

 

[mrgmhale]

The alternator will only put our what it is allowed to put out depending on the current sent to its field circuit (Orange wire with light blue stripe). Cleary 18.4 volts from the alternator is too high. To determine if the problem is cause by the regulator, the alternator, or some other cause, I would disconnect the Field Circuit at the alternator (do not let it touch bare. If, after the Field Circuit is disconnected at the alternator FC terminal, you are still getting 18.4 volts out of the alternator I would agree the alternator has a problem that is causing the field circuit to be getting current from somewhere it ought not be getting it. If the voltage is below 14.8 volts or so (likely 12 - 12.5v), the problem is not the alternator. With the 4 wire plug disconnected from the VR, check for voltage at the Field Terminal wire for the alternator (Orange with Blue Stripe). It should have no voltage. If there is voltage present you have a short in your wiring that is letting current feed into the Field Circuit even when the VR harness is unplugged. Once the VR 4 wire plug is plugged back into the VR you should then be getting some voltage at the Field Circuit terminal, as it is that current that tells the alternator to produce more or less output - depending on battery voltage.

My gut tells me your issue is most likely a VR that, despite being new, is allowing the alternator to get excessive current sent to the alternator's Field Circuit terminal. 18.4 volts is definitely excessive, and I am surprised you have not have more problems than a hissing battery. The battery hissing is not good, the battery is cooking off due to excessive voltage and heat, The plates inside the battery could end up becoming deformed which could cause plates to begin to contact each other in places they ought be contacting.

As for a replacement VR, if indeed it is sending excessive current to the Field Circuit, I am not sure where you are buying yours from, much less the brand. I personally like NOS Motorcraft, whether an older electromechanical or newer electronic design. If you must sue an aftermarket brand, I would stick with a high quality brand, such as Blue Streak.

Once you do resolve your charging system issue I hope you post what eventually did correct it.

 

[Billw69]

Thanks very much for the in depth discussion regarding this overcharge condition. As I mentioned earlier, I changed the VR with no resulting change to the condition. I have another alternator that I was going to put on the car for the sake of the simplest trouble shooting. Field circuit testing will be next.

Thanks again, and I’ll report back with my discovery

 

[mrgmhale]

FWIW, attached is a snippet from the 1973 Ford Shop Manual. Specifically it covers the charging system. It goes into more detail than I would want to retype, and offers specific specifications to test against. If you have not yet found the cause of overcharging, there is a section that covers that subject very thoroughly. I highlighted the opening portion of that section.

 

[detritusmaximus]

A hissing battery should only be used in Cobras.

And if you are losing coolant, it's a Spitting Cobra!

 

[Billw69]

Update; after following the direction of Mr. Hale and disconnecting the field circuit, the volt meter reading with the engine running was a steady 12.56, or battery voltage. So I assume the alternator is functioning normal.
Next I started the engine with the four wire plug out of the voltage regulator and read 0 voltage at the orange wire with the blue stripe. Engine running, I attached the four wire plug back into the VR and immediately heard the engine load up slightly, and saw the battery voltage begin rising toward the 18v figure again.

So it appears the VR and alternator are functioning normally.

Guess it’s time for my favorite job…….. searching for a bad wire or connection.

 

[Billw69]

Great resource, thanks for the heads up!

The search continues

 

[Don C]

Take your alternator to Autozone, they will test it.

 

[midlife]

I don't know if this may be the problem, but there are 2 variants of alternator harnesses: one for ammeter and the other for alternator indicator lamps. The ammeter version uses 3 of the 4 voltage regulator pins; the idiot lamp uses all 4. Many catalog stores still list the alternator harness incorrectly, so the description above is the best way to tell.

 

[72conv]

Update; after following the direction of Mr. Hale and disconnecting the field circuit, the volt meter reading with the engine running was a steady 12.56, or battery voltage. So I assume the alternator is functioning normal.

Someone correct me if I'm wrong here, but doesn't the alternator require field excitation to generate voltage? In other words, with the field disconnected, there would be no output?

Billw69, you mentioned that you have another alternator on hand and you were going to try it. How did that work out?

 

[Billw69]

Update; just replaced alternator and have the same over voltage (18+v) condition. I also agree, and Mr Hale said as well, that the field wire is what class for voltage or excites the field to put out voltage.
in the interest of full disclosure when I disconnected the field wire (at the alternator) and measured the voltage at the battery it made sense to me that it should read zero output (or 12.6v) at the battery. Also under full disclosure, I’ve been accused of being to literal, just ask my wife…., but that said maybe I was performing the field test incorrectly?
Guess I’ll start by cleaning up all the ground points I can….. like the strap to the fire wall from the intake manifold as well as the contact points for the VR.

Thanks again guys for all the suggestions.

 

[Don C]

The original grounding configuration was the ground cable run from the battery to the lower bolt on the voltage regulator and then to a bolt on the block.
https://www.cjponyparts.com/cj-clas...sa-made-mustang-250-302-351-1970-1971/p/BC09/