20 k secondary alternator not charging

[jims 20 k]

We have a 23 Thor 20 k on a 22 chassis. The secondary alternator charged the lithium batteries while the engine was running for the first 4 months then it stopped charging them. I backed into some high grass one time and since have checked all the wiring and fuses underneath the van but still haven’t figured out a solution for the issue and of course there are no dealerships or shops close to where we live. Any information would be helpful.

 

[16ACE27]

UHG failing is a common issue. Mark should be along to help at some point but in the meantime you can search the site for the issue.

Here's a thread to get you started: Sequence auxiliary alternator

 

[MCP-THOR]

The thread referenced by 16ACE is a great place to start. Some additional info would be helpful however.
1. Did it just happen?
2. Do you have 12v power at all, even when on shore power?
3. Do the batteries charge when on shore power, through the inverter/charger?
4. Has the temperature dropped, shutting down the battery BMS, thereby preventing charging? Looks like you could be in Sioux City.
5. Is the UHG (second alternator) spinning...and can you check for output with a clamp meter? (Not sure if a reading is possible if battery is not connected as in either a loose/disconnected cable or by the BMS shutdown.)
6. Does the Balmar gauge (or reading direct from the Balmar regulator) show any amps in? If you have the Balmar SG2-0300 Bluetooth dongle, it provides much more info and easier to both read the settings and also to change them if necessary.

Hopefully this helps a little. BTW, I have the same year and model, but with the 2-100ah batteries upgraded to 2-300ah.

Mike

 

[MCP-THOR]

Another obscure possibility is that the ignition sense wire (brown) is disconnected at the Balmar regulator (terminal 3 I believe) or is interrupted on its route to the alternator relay. That brown ignition sense wire is what can be used to turn the alternator on/off by adding ia switch is to it, according to the Balmar documentation.

 

[Mark54]

We have a 23 Thor 20 k on a 22 chassis. The secondary alternator charged the lithium batteries while the engine was running for the first 4 months then it stopped charging them. I backed into some high grass one time and since have checked all the wiring and fuses underneath the van but still haven’t figured out a solution for the issue and of course there are no dealerships or shops close to where we live. Any information would be helpful.

- There is a MRBF fuse atop the B+ buss bar underneath- so check that first. You should be able to check in place with a continuity tester, or VOM set on Ohms. Check all wires for tightness as well.
- Check the connections at the UHG and MC-618 Balmar regulator- my regulator temp sensor was installed backwards- reverse polarity, so i just got a new one. Find manual and check the wiring.
- The modular connector on the front of the UHG (grey w/ 4 pins) has 3 open holes that should be plugged as well- water getting inside can wreak havoc. The plugs I used are seen below- I used dielectric grease to install them with to seal against moisture.
- Check the belt on the UHG to make sure it's ok- earlier ones had the belt shred from poor clearances to the plumbing, or the belt cut the plumbing, and you'd see a puddle on the ground.
- Get a SG200 gateway and install to the Balmar gauge so you can see a 3rd readout on the Balmar App that shows the UHG operating and what it is doing, when engine is on. If you have that and no 3rd readout, (with gateway installed) then there is something wrong- so trace all the wiring and see if you can find a problem-
Boatyards/ marinas are more helpful than dealers since these were designed for marine application long before the RV industry thought of using them... so you could try going to them for help.

 

[Indoorgolf]

I am replying to this three months removed, but if you got a similar $1800 quote I got, maybe it’s still not fixed and we can compare notes, but it’s the identical description that I experienced with my 2023 sequence 20A. Seemed to work for a bit then nothing a few months in and even after spending north of $800 with General RV only to get a quote for $1800 more for $2600+ to replace the alternator which led me to buy a small champion generator that uses both propane and gas to get on the road until I figure out a more reasonable solution that I won’t just fail two years down the road according to what I learned from AI. In the final analysis it appears these alternators run themselves to death because the device that controls when they are supposed to run fails, causing them to run constantly and burn out. At least that appears to be the case with mine.

This was barely a 14 month old part and very expensive so I figured someone must be rebuilding them.

I agree with the other gentleman that a marine might give a far more reasonable solution. I’m not knocking the RV dealership. They were good people just very limited experience with this issue.
So did you resolve it?
Does anybody know of a company that rebuilds these alternators?
I’m heading to a marina next unless someone has a better source.
Then I will have my auto repair shop, replace it because RV dealers are about 2-3 times the labor cost with limited electrical repair knowledge compared to a seasoned auto mechanic.
Thank God for living in Michigan, where there are plenty of lakes/marinas and of course Auto Repair experts.

I will report back if I find a bargain because there must be hundreds of these sneaking up on others like us, post warranty.