Help Battery light on

[Allan]

I have a 2011 Thor Windsport 32-foot motorhome. The battery light kept coming on when I would climb a hill or at higher RPMs. So I replaced the alternator with a new one but that didn't make a difference. I then pulled apart the Bird system that I have and replaced the solenoid. I wasn't sure on the size of the solenoid, mine had no markings so I went with a 12V 300 amp. I took off on my next trip and all seemed well until after 180 miles, climbing up a hill, the battery light came on. Can anyone help me please!!!!
I failed to mention that as soon as I start going down the hill the light turns off.
Allan

[16ACE27]

I assume you mean the battery light on the dash? That's for the engine battery and charging system. Obviously, the parts cannon shot of a new alternator didn't fix it. Sounds like a bad connection to me aggravated by the tilt of the MH.

[Lt Keefer]

Is the alternator producing electricity? What is the state of your battery? Have you scanned the coach for any codes?

[Allan]

The battery is 3 weeks old and seems to be charging. Connections are clean at the battery terminal. Before I start the MH the battery reads 12.99 once the motor is started the voltage increases to 13.7 or so. New battery and new alternator and the belt is tight. I am totally at a loss! I dont have a volt meter gauge on the console of the MH so I have to stop and open up the engine area to measure the voltage, by then the battery light goes off.

[Lt Keefer]

I guess you'll need to trace the wire back from the alternator. You may have a back connection as previously stated. Look for the green crusty mess at connections.

[16ACE27]

Originally Posted by Allan

The battery is 3 weeks old and seems to be charging. Connections are clean at the battery terminal. Before I start the MH the battery reads 12.99 once the motor is started the voltage increases to 13.7 or so. New battery and new alternator and the belt is tight. I am totally at a loss! I dont have a volt meter gauge on the console of the MH so I have to stop and open up the engine area to measure the voltage, by then the battery light goes off.

[Allan]

That is a great idea, I hadn't thought of that. Also thanks for the voltage reader that I can just plug in. I can see what is happening under the hood without stopping on the side of the road.
Thank you all.
Allan

P.S. Does anyone know what type or size the solenoid needs to be on my Bird system? I just guessed at 12 volts and 300 amp. There were no markings on my old one.

[Bob Nodine]

This can often happen in vehicles with more than one charging source. We had a diesel pusher that would sometimes turn on the alternator fail lamp if the generator and the engine were running at the same time. One trick to try is when this happens turn on the headlights. Sometimes the voltage drop caused by turning on the head lights will extinguish the alternator lamp. Do you have a solar charging system? I don't think any harm is done when the alternator lamp is on under these conditions but it is annoying.

[Allan]

Thank you for your reply, Yes I do have a solar charging system. I will try the headlight idea.
Allan

[16ACE27]

Originally Posted by Allan

That is a great idea, I hadn't thought of that. Also thanks for the voltage reader that I can just plug in. I can see what is happening under the hood without stopping on the side of the road.
Thank you all.
Allan

P.S. Does anyone know what type or size the solenoid needs to be on my Bird system? I just guessed at 12 volts and 300 amp. There were no markings on my old one.

That's what the original Trombetta solenoid was rated at. It does need to be a continuous duty solenoid through.

[OldWEB]

Originally Posted by 16ACE27

EXACTLY what I use in the console to watch the chassis battery volts (and connect USB devices) and I installed a surface mount one in the galley area to monitor the voltage of the coach batteries (and USB things). At night they are as bright as any nightlight you may need.
Always can see if one system is charging the other (or not!).

[Allan]

Thank you both, I have a monitor ordered and it should arrive today. That is the solenoid that I ordered.

[Jimbo56]

Ace, do these things have a separate voltage regulator like back in the old days.to the OP -is your dash ac running when this happens going uphill? Is it designed to shut off the compressor when under heavy load? Just thinking out loud.

[16ACE27]

Originally Posted by Jimbo56

Ace, do these things have a separate voltage regulator like back in the old days.to the OP -is your dash ac running when this happens going uphill? Is it designed to shut off the compressor when under heavy load? Just thinking out loud.

I don't think anything works like back in the old days.

Most GMC vehicles use a "one wire alternator" so the voltage regulator is integrated into the alternator.

Ford trucks used external voltage regulators longer; I'm not sure what his year used but the "battery light" historically has been wired into the alternator charging circuit such that if current flowed out of the battery instead of in, the light would light.

Of course everything is moving to control by the multitude of computers in vehicle theses days, ECM, PCM, BCM, etc.

[Allan]

That all makes sense, I drove over 200 miles with the battery light on, and when I got to my destination that battery had a full charge. This whole thing is very puzzling to me.

[ArcticGPS]

Check the fluid level in the chassis battery. If you are going up a hill, maybe there is a cell a little light on water. The top of the plates are exposed - and it reports an undervolt. You level out - connection reestablished.

[Allan]

Thank you for your help, I did check the battery level, all 3 batteries are full.
Good idea though.
I just installed a switch on my solar panels that allows me to turn them off. I will take it out and see if that makes any difference.
Allan

[16ACE27]

Originally Posted by Allan

Thank you for your help, I did check the battery level, all 3 batteries are full.
Good idea though.
I just installed a switch on my solar panels that allows me to turn them off. I will take it out and see if that makes any difference.
Allan

Just FYI - The house batteries have absolutely nothing to do with the dash "battery" light.

[EA37TS]

Interesting info.

https://www.pipsisland.com/the-battery-light-comes-on-and-then-goes-off-when-accelerating/#:~:text=In%20these%20cases%2C%20you'll,or%20a%20d amaged%20serpentine%20belt.

[simidrm]

Throw that trombetta solenoid in the trash, I replaced mine 3 times and replaced the bird once, finally found a 900amp continuous duty and never had a problem after that