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rpmattison · 02-15-2025, 06:47 PM

Headed south yesterday from upstate NY everything went well last night but when we wanted to start out this morning the engine would not start so we jump started it and drove til supper. After supper we started the engine again. We turned the headlights on after supper tonight the headlights were dim. Stopped at an autozone and had them check the engine battery and it checked out fine. Thought it might be the alternator but the employee said he couldn't check the alternator (Really?). So we disconnected the battery to see if the engine would continue to run and it did. He said it's not the alternator? He suggested taking it to a mechanic in the morning. We are stuck in Richmond and I'm not sure the employee knew what he was talking about (makes sense but I have never heard of testing it that way). Am I stuck with finding a mechanic on Sunday morning or do any of you have an idea that may get me out of this bind?

Country Road · 02-15-2025, 07:05 PM

Quote:

Originally Posted by rpmattison

Headed south yesterday from upstate NY everything went well last night but when we wanted to start out this morning the engine would not start so we jump started it and drove til supper. After supper we started the engine again. We turned the headlights on after supper tonight the headlights were dim. Stopped at an autozone and had them check the engine battery and it checked out fine. Thought it might be the alternator but the employee said he couldn't check the alternator (Really?). So we disconnected the battery to see if the engine would continue to run and it did. He said it's not the alternator? He suggested taking it to a mechanic in the morning. We are stuck in Richmond and I'm not sure the employee knew what he was talking about (makes sense but I have never heard of testing it that way). Am I stuck with finding a mechanic on Sunday morning or do any of you have an idea that may get me out of this bind?

You don’t give any information about your coach or how old the chassis batteries are.

For what it’s worth, I would install new chassis batteries, betting on the guy checking them out not having a clue. Unless you can tell otherwise that they’ve been recently replaced, and then they still could be bad.

It could be your alternator or something else, but once again, how old is your coach?

US1 · 02-15-2025, 07:08 PM

It's easy to check if the alt is out putting. Check the battery voltage without the motor running. Then start the motor, if the voltage goes up, the alt is charging

rpmattison · 02-15-2025, 07:44 PM

Quote:

Originally Posted by Country Road

You don’t give any information about your coach or how old the chassis batteries are.

For what it’s worth, I would install new chassis batteries, betting on the guy checking them out not having a clue. Unless you can tell otherwise that they’ve been recently replaced, and then they still could be bad.

It could be your alternator or something else, but once again, how old is your coach?

2013 Tiffin - just bought it last year not sure of battery status. Both batteries checked out ok Ford chasis

twinboat · 02-15-2025, 07:47 PM

The kid removing the + battery cable on a car or pickup is a crude test, it shows alternator is creating voltage in place of the battery, but not on a motorhome with house and chassis batteries combined while the engine is running.

Depending on your rig, you may be able to run the generator and keep the chassis battery charged, even with a bad engine alternator.

rpmattison · 02-15-2025, 07:52 PM

Yeah, I didn't trust his judgement or knowledge - gotta get to a mechanic tomorrow.

NXR · 02-15-2025, 08:23 PM

Quote:

Originally Posted by rpmattison

2013 Tiffin - just bought it last year not sure of battery status. Both batteries checked out ok Ford chasis

What does "both batteries" mean? There is only one battery to start the engine of a Ford gas motorhome, up underneath the hood on the passenger side.

Do you have a switch up front labeled Battery Boost or similar? If so, and it's spring loaded, hold it down for about ten seconds and while holding it down attempt to start the engine. Once the engine starts then you can release the Battery Boost switch.

That jumps the house batteries, probably the two that were checked, to the engine battery up front and can allow the engine to start.

Also, with many coaches, you can start the generator and it will charge both the house batteries and also power the engine electrical system. Many a person who had an engine alternator failure has done that and kept on driving with the generator running until they got to somewhere that a repair could be effected.

I would hope a Tiffin is wired that way but I have no idea.

Ray

d23haynes57 · 02-15-2025, 08:37 PM

Not only is disconnecting the batteries to test the alternator a poor test it is destructive. Generally, it will spike and possibly damage the alternator but can also take a lot of electronics in the vehicle. I would be surprised if the instrument panel does not have a voltmeter. That will display the system status and inform if the alternator is keeping up with the loads and maintaining voltage. Engine running you want to see at least 13.5 volts with some changes based on load. Important to pay attention to this as sudden loss of voltage may also be an indication of belt failure that may also be used to operate water pump or fan drive. Understanding this is almost as important as tire pressure and coolant level, alongside oil level and pressure.

This will sound a bit obnoxious, but all those gauges are there for various reasons, mostly protecting the investment. Operating an RV also requires a bit of technical knowledge. Sometimes part technician and part engineer. It is wise to have some tools and test equipment. A multimeter preferably with clamp on amp meter will allow you to diagnose many ills and also allow someone more knowledgeable to help when needed.
If your alternator did fail, you may be able to use the generator-house battery charging system to charge the chassis batteries to get you going again.

dabrooks · 02-15-2025, 09:03 PM

I have a 2013 Tiffin 35QBA on a Ford chassis and it did not charge the chassis battery from ground hook up or the generator. I added a TrikL Start which added that feature but that is no longer available.

I suspect you have a bad chassis battery or a bad connection. How old is the chassis battery.

I drove home 350 miles and when I got home and unpacked the rv wouldn't start. The chassis battery was dead.

NXR · 02-15-2025, 09:39 PM

Quote:

Originally Posted by dabrooks

I have a 2013 Tiffin 35QBA on a Ford chassis and it did not charge the chassis battery from ground hook up or the generator.

Thanks. Is there a Battery Boost switch or similar?

Ray

SafariBen · 02-15-2025, 09:46 PM

Not starting in the morning is not a surprise, lots of things can drain the battery over night. Running all day indicates the alternator is working fine. The headlights dimming is suspicious, but I'd want to know the voltage at the chassis battery, then precede to all the other reasons the lights could be dim. Not exactly a rare problem on RVs.

Basically, VOLTS is the answer. I have a couple cigarette lighter plug in USB chargers with digital volt displays, makes it easy to keep track. A multimeter and the basic knowledge of how to use it is valuable with anything over ten years old.

dabrooks · 02-16-2025, 06:01 AM

Yes on mine there is a battery boost switch to the left of the steering wheel. When mine wouldn't start the battery had a dead short in it or something and it would not start with a jump.

d23haynes57 · 02-16-2025, 06:17 AM

Quote:

Originally Posted by SafariBen

Not starting in the morning is not a surprise, lots of things can drain the battery over night. Running all day indicates the alternator is working fine. The headlights dimming is suspicious, but I'd want to know the voltage at the chassis battery, then precede to all the other reasons the lights could be dim. Not exactly a rare problem on RVs.

Basically, VOLTS is the answer. I have a couple cigarette lighter plug in USB chargers with digital volt displays, makes it easy to keep track. A multimeter and the basic knowledge of how to use it is valuable with anything over ten years old.

Dimming headlights while underway is usually the first sign of a charging system failure. And if the house batteries are ignition switch relay controlled by the time you notice the headlights dimming both house and chassis battery banks are now compromised. This is when you want a truly capable house battery charging system that can also connect to the chassis batteries. Get the genny started and use the house battery charger to keep you going.

OMMM4747 · 02-16-2025, 07:28 AM

Quote:

Originally Posted by rpmattison

... everything went well last night but when we wanted to start out this morning the engine would not start so we jump started it and drove til supper. After supper we started the engine again. We turned the headlights on after supper tonight the headlights were dim.

Batteries: Although you don't state how long you were plugged to shore power, it's obvious the batteries did not charge. Whether or not your coach is designed to charge the chassis batteries while on shore power, you'll have to determine on your own. 12vdc does not necessarily indicate 'good batteries' if they're old, unable to hold a 'good' charge, and subsequently lack the cranking amps to turn the engine. In the latter case, when you turn the key the volts drop off and do not recover, thereby no cranking amps. How old are your batteries? How well have they been maintained? Upstate NY? Pretty cold up there and that doesn't bode well with old and/or weak batteries. Unless you're certain they're 'new', I'd replace them. You've already had one deep discharge cycle that you're aware of and will likely have more.

Alternator: Yes, its output can be checked with a multimeter and the engine running. It should be providing greater that 14vdc. The dim headlights could be either the batteries or the alternator. Testing requires 2 people: one starting the engine and the other at the chassis batteries to see what they do during starting and what the alternator is doing after, and if, it starts.

If it's the batteries, it's an easy and cheaper fix. If it's the alternator and you have a BATT BOOST feature, you can limp to a repair facility. Otherwise call for a mobile repair. Work w/your roadside assistance company if you have one.

If you're going to DIY a battery change, label and take pictures of all connections so as to not make reassembly a guessing game. Ensure you get batteries w/at least the same rating -- cranking amps -- as your current batteries.

One last possibility ... presuming your coach is capable of charging the chassis batteries and along with being able to start the coach after supper, it could also be an inverter issue since the alternator did charge the batteries and you were able to restart after supper. However, the dim headlights would indicate the inverter not to be the culprit, but more troubleshooting would be required to confirm that.

Good luck