Blown fuse and circuit board in Harman XXV

[Frenche66]

This will make the 3rd circuit board replacement on our 4 year old Harman XXV. Every time the stove power is off and it's turned back on the fuse blows, as well as the circuit board. Isn't the point of a fuse to protect the board? The board we just received is the same 3-20-05886F but the fuse is not the 6 amp that they've been coming with. This one is tiny and I can't read the size. My question is what could be causing this? My husband (electrician) has checked everything and a Harman repairman has checked it over several times as well.

 

[Ssyko]

There is a dead short somewhere in the harness. With the scorching it looks like it's the power input side of the board. Has the hubby verified the voltage feeding the stove?

 

[Frenche66]

Every time it has happened that is one of the first things he's checked. The service man checked all the wiring in the stove and says it looks good, but maybe I'll have my husband check it again. We even replaced the ignitor the second time it happened at his suggestion. The stove shop, which hasn't been helpful, stated it might be my battery backup, but I'm now on my third and always the recommended by Harman one. This time its the $500.00 Surefire 512. This is getting more expensive than oil.

 

[Frenche66]

Also, I found it strange that on this new board the fuse is half the size. Maybe they figured out the fuse wasn't protecting the board?

 

[Overfireinthehole]

i had an xxv do that once. Basically tried everything you folks have tried and would’ve kept on but the customer decided I didn’t know what I was doing because I couldn’t figure it out. It would go months between times it blew the board, and everything always looked great after replacing the board. They had it on a high dollar protector too. I wish the customer would’ve let me take another crack at it, cause it’s bothered me ever since. I only charged them for the first service call and gave them free parts and labor twice afterwards cause I felt bad I couldn’t catch it. One thing I have seen many times on the xxv is that the wire harness tends to get pinched when it leaves the board compartment and enters the rear of stove. There’s a little rubber grommet it passes through but if that grommet falls out, the metal can pinch a wire in two. Hope you get it figured out.

 

[Ssyko]

You may be able to trace down a problem circuit by adding a 2amp fuse to the hot side of each component ( igniter, combustion motor, convection motor, etc.). It will protect the board from a component failure/short. But if there is something wrong with the harness it could still smoke a board. I would inspect every inch of the harness, removing wire ties as necessary. The difference with the fuses is probably an engineers design change in the circuit layout and bean counters way of saving $$$. It will be the same size (amperage) but smaller physical size.

i sent a pm.

 

[Frenche66]

You may be able to trace down a problem circuit by adding a 2amp fuse to the hot side of each component ( igniter, combustion motor, convection motor, etc.). It will protect the board from a component failure/short. But if there is something wrong with the harness it could still smoke a board. I would inspect every inch of the harness, removing wire ties as necessary. The difference with the fuses is probably an engineers design change in the circuit layout and bean counters way of saving $$$. It will be the same size (amperage) but smaller physical size.

i sent a pm.

Well that is dissappointing, I was hoping that maybe Harman found an issue with their boards. We've replaced the igniter and the distribution fan already. I guess I'll have to make a list of the other items and check. Kind of frustrated that I've spent this much money on a stove and follow all their safety precautions and have problems like this. I'm glad it was before my son and mother made their purchase. We're now researching and looking for recommendations on other make and models.

 

[Overfireinthehole]

This kind of thing can happen on any stove. I’ve only ever had one xxv with this problem and we’ve probably sold 300 of them. I had an auger motor that was blowing fuses on a different stove once but it did it any time the feed kicked on which was easy to track down. I’ve had several igniter wires do this before as well because the high temp insulation wears off overtime.

 

[koloki]

Hi, I know this post is old and I am not sure someone will see it but still I try! In case a solution was found.

I am confronted to the exact same problem. On the Harman XXV too, with a European 230V board.

Each time the fuse burn, the red varistor burn too at the same time. Like you can see on the first picture.
The first time I changed this varistor and the stove worked again for an entire winter (I was quite proud of myself!)

But after this summer there were both destroy again. So I replaced the varistor again and add a surge protector on the plug. But it only worked for 2 weeks.

Now I don't know what to do.

Each time they burnt, the stove was off. Each time the main circuit-breaker went off. From then if I only replace the fuse it is destroyed as soon as I plug the stove in but the circuit-breaker stays on.

I look attentively to every wired and connexions in the stove, everything looks fine. I have no clue.

Can a defective organ (such as a ventilator) could burn a varistor ? (not in my understand as it protects from too much voltage until 390V that come from the plug but the surge protector would preserve from that).

Please help!

 

[rickwai]

I have seen Harmans in the past blow the fuse from a bad Combustion motor. The tell tail clue that I have found for it is if the fuse blows as soon as the stove is plugged in. The fan pulses on for a second. That is the only thing running at that time. Then I replace fuse and unhooked Motor to verify.

 

[koloki]

Thanks. I am not sure since the fuse now blows because the varistor is dead and I am pretty sure if I'd replace the varistor the fuse won't blow asap. But still it is a good suggestioon and I will have a close look to this fan.