945 seat motor fire

Contact Volvo Customer Service & tell them what happened as this is a issue that I have not run in to yet. Do not know what help they may or may not offer you but it can not hurt to go on record with them about this Glenn

Yikes! Can you tell where the fire started? Was it the motor itself or the wiring? It's entirely possible that a wire chafed, grounded out, and had enough resistance that it didn't blow the fuse before heating up hot enough to burn the insulation off, though it does surprise me that it actually caught fire, that's kinda scary.

Best I can suggest for parts is a wrecking yard, or see if you can file an insurance claim and get the parts from Volvo, but a wrecking yard is sure to be far cheaper, even a nicer one with newer cars.

What probably happened is that the seat heater overheated and shorted to the motor and burned out the motor fuse but continued to burn the seat. That explains why when the fuse burned out it didn't stop the fire, it was the wrong fuse. The seat heater can cause a fire and does when the thermostat fails.

Seat heater is fine. Fire under seat centered at motor and controller unit.

Howard

It was probably the wire, or maybe a connector that overheated. I've shorted a couple wires connected to high current 12v sources before and it's shocking how quickly the insulation practically vaporizes, though I haven't yet had one actually catch fire.

What is there to burn in a motor? The control unit is the biggest candidate. I had a smoke detector that started a fire. Control circuitry can start fires easily. When I was a physicist at AT&T, one of my jobs was designing electronic components so they were not flammable. The plastic parts are very flammable and once the fire is started the fire continues even after the fuse blows. We solved the problem by making all components connected to the power source non-flammable. They were made of flammable resins but were designed so they would always fail safely by cracking before they ignited. This always prevented a fire.

The fuse is to keep the wire from catching on fire. The way to prevent fires is to have a smaller section of bare wire that melts before the insulation catches on fire (i.e., a fuse or fusible link). When I did this type of work I had a 200 amp power supply and could make just about anything catch on fire.

Reminds me that I should really get fire extinguishers to keep in my cars, I've seen enough cars of all makes burned to a crisp in junkyards and heard just enough stories that a $20 compact extiguisher is cheap insurance.

In an ideal world the fuse would always blow to prevent a fire, but it's entirely possible for a connector to corrode enough to limit the current just enough to burn up the wire without actually blowing the fuse.

This I don't believe. I spent a lot of time flame testing wires and only wire smaller than 20 gauge would burn at less than 20 Amps. The rating on wire is not for flammability, but voltage drop. At their rated currents they don't even get warm.

I've seen heat damage in a circuit where the fuse doesn't blow, but it's always been at some sort of connection, where I guess resistance from poor contact can create enough heat to cause melting and fires.