Lochinvar Noble Combi Fan Speed Lockout

mattc

Hi there,

I have an NKC 110 that has been operating just fine until a few days ago. I came home to a "Lockout Fan Speed" error. I reset and it started, but the fan speed on the display was varying wildly, like 10,000 to 0 back to 8,000 to 0. Then it locked out again. I looked up the troubleshooting guide and ran through everything. Fuse fine. Air intake clear. All connections looked good. I just happen to have an additional control board, so I installed that and got a reading of 0 rpms, and it locked out. I found another forum in which a tech was complaining that a fan speed lockout is always the fan. I then ordered a new fan. Tonight I installed the new fan. I know it's running, I can hear it and I can feel air being pulled in through the inlet. Still showing 0 rpms and locking out. Any ideas?

TomS

I would suspect the wiring and connectors between the fan and control board. The fan gives a signal to the control board as to its speed. The control is doing its job by shutting down since it is sensing only 0 rpm while it is telling the fan to operate at a higher speed. Try moving the wires before shutdown to see if any change takes place.

GroundUp

I install a lot of Nobles and while I have not had this particular issue, I know that the ribbon cables from the board are VERY particular. Even a slight kink can cause erratic behavior. Do yourself a favor and call tech support while you're standing in front of the unit with a combustion analyzer, and they'll take care of it

mattc

I tried moving the wiring some while it was trying to start and no change.

Jamie Hall

Let's think about this for the moment. The control board says the fan speed is 0. OK, is it? What is the fan actually doing?

If the fan is actually turning, it will be turning at a fairly constant speed — not varying wildly. So we have a communication problem, not a fan problem. Connectors. Every pin clean? Every pin and socket reasonably tight? Connector locked in? Every wire actually intact? All grounds clean and tight? Look at the board. All solder connections good? Nothing got cracked or pulled loose (not that hard to do when wrestling with a plug soldered to a board)?

mattc

Jamie,

I checked all the connections and they're solid, but I'll give it another look.

As for what the fan is doing, you're right, it's running at a constant speed until the lockout happens. I'm now thinking I probably didn't have to spend the money on a new fan, but at least I know that's not the issue. (unless I have a faulty fan, which is within the realm of possibility.)

joseph annon

A quick test to see if the fan is getting power and runs to speed is to unplug the low voltage connector. When you unplug the low voltage connector the fan will run at max speed. This tells you the fan is not seized but does not tell you if the internal control is working or if the input control is working.

mattc

Update:

Spoke to Lochinvar and the tech agreed with all I've done, then had me check continuity on the 4-pin connector. The black wire has no continuity. Does this mean I have to buy a whole new wiring harness? Or does anyone know?

Jamie Hall

Unless you have the skill to take that connector apart and repin it and get it back together, then yes — a new harness.

mattc

I've ordered a new wiring harness. The lack of continuity absolutely meant that the communication error was a bad wire. I've always been confused on exactly how a perfectly good wire could just quit without any warning, but I guess that's just how it works. So, I get a new harness tomorrow and hopefully I can take a hot shower soon.

Jamie Hall

Try working on a Chrysler product.

Dave Carpentier

Pin could have been inserted poorly into the connector. Do the pins all look to be the same distance in from the connector face ?

Pull on each wire while watching the pins end. It will likely wiggle, but shouldnt translate in and out