Persistent High Temperature Alarm

Q&A and troubleshooting
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I have a High Temperature Alarm that will not go away, despite definitely not having high temperature.

Background: my system has been set up and working great for several years now and I know its capabilities and limitations fairly well at this point.

The other night, we lost power unexpectedly. I checked the app and it had a high temperature alarm, even though the inverter was only reporting 59F (15C), and we were not doing anything particularly strenuous with the system.

Went out to check out what was going on and found a mouse has gotten into my inverter (MultiPlus 24/3000/70-50 120V), built a nest in between the heat sink and the cooling fan completely blocking airflow in between, and for good measure had eaten through the red wire of the cooling fan.

Yep. That’ll do it.

So I evicted my unwanted tenant, disconnected and unmounted the inverter, removed the various metal plates to get at the insides, cleaned everything out real good, and repaired the broken wire. Put the whole thing back together again and hooked it back up. Confirmed the fan is working. But as soon as I turn the inverter back on, it reverts to giving me a high temperature alarm, even after sitting for 45 minutes now and the ambient reading is 39F (4C).

The only other suspicion I have is that, while I was inspecting the inverter for any other damage, I didn’t see much except for some nibbling on the insulation of a brown twisted pair of wires going to the upper PCB. It exposed the metal wires in a few places. But didn’t look bad enough to cause a short in any direction. I know, it would have been best to replace them anyway, but I was focused on doing just what is necessary to get back up, and I had limited supplies.

So…does anyone know what those brown wires are? Could they be related to a failsafe temperature sensor that reads failure if it can’t make a connection? Or are they unrelated to this problem? If the latter, any other ideas why it’s still giving me the high temperature alarm when temps are just above freezing and the inverter has been off for over 24 hours?

Please, if you would, no Captain Hindsight responses. I know this was my fault. I know I should have protected it better and I will do that next. But I’m just trying to get us back up and running first.

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A couple of other pieces I forgot to mention:

  • I am completely off grid. No grid tie.
  • I live in upstate New York.
  • The cooling fan continues to run constantly, which in my mind confirms that the inverter thinks it’s too hot.
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Alright. So. Posting this here for posterity’s sake. I called and talked to a Victron repair technician. Those brown wires are indeed going to the temperature sensors on the transformers. Apparently those wires were more damaged than I thought. As a test, I ran an experiment. I pulled the connector off the PCB and bridged the pins with a screwdriver, and the High Temp warning instantly went away. Pulled the screwdriver off it and it came right back. That’s not a solution obviously, as that just bypasses the safety shutoff . So apparently I need to get back in there and replace those wires.

Just in case someone else runs into something similar.

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