Low Voltage - 2005 XC Cat C7

[mdgpl]

An interesting day on the road. Left Key West at 10:30AM. All was fine for 2-3 hrs until I came up out of the keys and onto the expressway around Miami. Thats when the dash alert came on and the display was blinking "low voltage" and was reading 11.5 volts.

Anyway, for the next six hours I drove to Tampa. When i was coasting or stopped, the voltage would climb up to 12.1. When I'd get back to highway speed, it would drop down to 11.5 again. I shut off everything electrical like the front AC, the rear camera, made sure nothing was plugged in an charginging, and around 60-65 I could maintain 11.6 volts. I turned on the Gennerator so the charger would trickle the battery as well. It would drop down to 11.5 and I'd let the speed drop off for a couple miles, get 11.6 back, and then continued on. Lucky for me, I got stuck in 3 x 45min slow-downs of 10-15 mph so during those periods, I'd see about 12.1 again.

Dusk came, and I had to turn on my running lights, and then at 50mph for the last 30min, I saw 11.5. The good news is that I did make it to my destination with some dim lights the last couple miles.

So, experts, what's going on? I assume the Alternator / Regulator is shot, but the behavior seems backwards. My experience with an Alt going bad is that higher RPMs = higher voltage. Maybe the electornics on the C7 just has a greater load...

Next, anyone happen to have 2005 that they changed the Alternator and have the part number? I'm sure my day tomorrow will be exciting dealing with various parts counters looking for a replacement. Perhaps I'd be best off removing the old one and taking it with me....

[rarebear.nm]

Yes take it with you. You'll need for a core exchange.

[Ted DuPuis]

Yes, your alternator is bad. That's just like how mine failed.

You probably have a Leece-Neville style alternator. On my 2000 Endeavor with a 3126, it was a 160 amp. I replaced mine with a 270 amp one, which bolted in and gives more capacity all around. I also converted my setup to dual alternators, so the Leece-Neville powers the house side and I added a 28si which powers the engine side. I did a video on my dual alternator conversion (which is excessive and done to help support some other upgrades I did).

There are sources online where you can order new alternators. If you're on your way home, you can limp home using the generator. What I did was I connected the house batteries to the engine side batteries (just moved the battery cable from the "aux start" relay) and ran the generator. It worked just fine and let me get home where I could fix this problem easily. As long as your alternator isn't making any bad noises (in other words, so long as it's not a bearing going out) then you should be able to do this without a problem. If you aren't sure what I'm talking about, I can take a picture of what this area looks like from my RV (and since mine is a 2000, it's possible yours is different, but I think this part is more or less the same).

[Toribk]

Just curious, how old is your chassis batteries?

Sent from my SM-G955U using iRV2 - RV Forum mobile app

[JNSNWT]

[QUOTE=Ted DuPuis;6430978]
I replaced mine with a 270 amp one, which bolted in and gives more capacity all around.

Going from a 160 amp alternator to a 270 amp one will give you more capacity to run accessories but it won’t shorten the length of time needed for recharging the batteries. Is this a true statement?

[wolfe10]

While a failed alternator IS quite likely, you really need to troubleshoot the charging system to VERIFY it is the culprit.


I would start troubleshooting at the battery isolator after checking that all connections at the alternator are clean and tight. Same for connections at the batteries.


And, as long as house bank voltage was sufficient for a smart inverter/charger to take over charging duties (likely around 12.0 VDC) the generator powering the inverter/charger should have been able to maintain voltage in the 13's. And by either using the boost switch or moving one wire on the battery isolator, you could drive cross country with no alternator output.

[Ted DuPuis]

Originally Posted by JNSNWT

Going from a 160 amp alternator to a 270 amp one will give you more capacity to run accessories but it won’t shorten the length of time needed for recharging the batteries. Is this a true statement?

That depends on how much/how fast the batteries can absorb the current. But overall, yes, that's correct.

Also, I significantly upgraded the wire coming from the alternator in doing the upgrade. That's important since otherwise the thing will melt.

I had several reasons for my upgrade - including wanting to be able to fully power the inverter for any electric needs while driving down the road without running the generator. It's successful at that.

[FIRE UP]

Originally Posted by mdgpl

An interesting day on the road. Left Key West at 10:30AM. All was fine for 2-3 hrs until I came up out of the keys and onto the expressway around Miami. Thats when the dash alert came on and the display was blinking "low voltage" and was reading 11.5 volts.

Anyway, for the next six hours I drove to Tampa. When i was coasting or stopped, the voltage would climb up to 12.1. When I'd get back to highway speed, it would drop down to 11.5 again. I shut off everything electrical like the front AC, the rear camera, made sure nothing was plugged in an charginging, and around 60-65 I could maintain 11.6 volts. I turned on the Gennerator so the charger would trickle the battery as well. It would drop down to 11.5 and I'd let the speed drop off for a couple miles, get 11.6 back, and then continued on. Lucky for me, I got stuck in 3 x 45min slow-downs of 10-15 mph so during those periods, I'd see about 12.1 again.

Dusk came, and I had to turn on my running lights, and then at 50mph for the last 30min, I saw 11.5. The good news is that I did make it to my destination with some dim lights the last couple miles.

So, experts, what's going on? I assume the Alternator / Regulator is shot, but the behavior seems backwards. My experience with an Alt going bad is that higher RPMs = higher voltage. Maybe the electornics on the C7 just has a greater load...

Next, anyone happen to have 2005 that they changed the Alternator and have the part number? I'm sure my day tomorrow will be exciting dealing with various parts counters looking for a replacement. Perhaps I'd be best off removing the old one and taking it with me....

mdgpl,
You say you have an '05 with a C-7 correct? But, you don't say what model coach/chassis. I don't like assuming all coaches are the same but, can I assume you're in a Winnebago or Itasca product? Just wondering. We also have have 160 amp Leese Nevile and so far, knocking on my head, it's been great for 106,000 miles. I recently, as in about a year ago, purchased a new 160 amp duplicate Leese Nevile and its sitting in one of my bays in the coach. Hopefully, I'll NEVER HAVE TO CHANGE IT ON THE ROAD. I've been in that engine compartment waaaaaay tooo many times and am not fond of it. Keep us informed of your progress.
Scott

[Ted DuPuis]

Originally Posted by FIRE UP

mdgpl,
You say you have an '05 with a C-7 correct? But, you don't say what model coach/chassis. I don't like assuming all coaches are the same but, can I assume you're in a Winnebago or Itasca product? Just wondering. We also have have 160 amp Leese Nevile and so far, knocking on my head, it's been great for 106,000 miles. I recently, as in about a year ago, purchased a new 160 amp duplicate Leese Nevile and its sitting in one of my bays in the coach. Hopefully, I'll NEVER HAVE TO CHANGE IT ON THE ROAD. I've been in that engine compartment waaaaaay tooo many times and am not fond of it. Keep us informed of your progress.
Scott

The L-N alternator on my 3126 is pretty easy to change being on the top. It’s also useful to keep a shorter belt to bypass the alternator in case it fails on the road (had to do that once).

With my current setup I can end up removing that serpentine drive belt entirely and the bus will still be fine, since the water pump has its own belt and I now have electric cooling fans. I can run the generator for the electrical system if needed.

[mdgpl]

Thanks all for the feedback. I'll be digging into this later today. To answer a few questions, Our coach is a Fleetwood Discovery 39L. I did run the generator on the way home. The house bank about 2yrs old, and read 13.8 the entire trip. The chassis batteries (2 x group 31s in parrallel) for the engine are < 1yr old. The Aux Start switch didn't seem to make a difference when going down the road so I will be checkin on the relay for that today as well.

The replacement alternator arrives today around 4:30PM, so I have time to take the old one out and take it with me to get bench tested.

First task of the day is taking the master bed apart, empty the closet and take up the closet floor so I can get at this from the top side (I looked at going in through the battery compartment, taking out the air-box, but I'm not limber enough for the manuver anymore... ). Wish me luck. I'll report back later.

[wolfe10]

Originally Posted by Ted DuPuis

With my current setup I can end up removing that serpentine drive belt entirely and the bus will still be fine, since the water pump has its own belt and I now have electric cooling fans.

Please, this is VERY important to stress to all who have the OE fan-- DO NOT DO THIS-- YOUR FAN (REAR RADIATOR) IS DRIVEN BY THE SERPENTINE BELT.


And, some late model Caterpillar C7's have the water pump driven by the serpentine belt as well.


Bottom line is to verify exactly how your engine-accessories are driven before going to "Plan B".


But, as many of us have said, the fact that the alternator is not charging (bad alternator, loose connection, bad battery isolator, etc) should not keep you from driving. Just run the generator to power the inverter charger to keep the house bank charged and either use a constant duty battery boost/combine switch OR hard wire the connection between chassis and house banks to keep the chassis battery charged.


Do NOT drive with below 12 VDC-- the engine and transmission computers which are 12 VDC are what keep you off the side of the road.

[Ted DuPuis]

Originally Posted by wolfe10

Please, this is VERY important to stress to all who have the OE fan-- DO NOT DO THIS-- YOUR FAN (REAR RADIATOR) IS DRIVEN BY THE SERPENTINE BELT.


And, some late model Caterpillar C7's have the water pump driven by the serpentine belt as well.


Bottom line is to verify exactly how your engine-accessories are driven before going to "Plan B".

Yes, 100% correct - I guess I didn't make that quite as clear with my post. This works for me because of how I've got my bus set up.