This 2000 Chevrolet Express van came in with the complaint that it had caught fire while sitting in a parking lot. Luckily the fire went out before any major damage was done. The source of the heat was the blower resistor and it’s harness connector but there was a lot more to the story than meets the eye.
I removed the blower resistor and started enlarging the hole per the supplied instructions when I noticed leaves down in the evaporator case.
The hole needed to be enlarged to match the pattern in the third and fourth drawings. Luckily the melted plastic did not extend further or I would have needed to make a cover plate.
Now I needed to get the leaves out. This vehicle would have been severely damaged if those leaves had caught fire. Believe it or not those leaves were third on the list of the causes of this problem.
Since the resistor hole is not large enough to remove the leaves, I also had to remove the blower motor. There is one 10 mm headed screw that holds the radiator overflow/expansion tank in place at the lower edge.
The two tabs at the top edge will then slide out of their respective slots and the tank can be set aside.
Just a few screws and one harness connector and the blower motor is easily removed.
I know the picture is not clear but there were a lot of leaves in this evaporator case.
I placed my shop vacuum hose in the blower opening and started pulling the leaves out.
I assisted the leaf removal by using an air hose to blow the leaves free from their resting places. Look closely at the plastic around the terminal end of the red wire on the blower resistor harness connector. The red wire only supplies power to the high blower relay contact and will only be damaged if the high blower speed is over used. It does not supply power to any other blower speed.
Another blurry picture but hopefully you can see that the leaves are gone.
I installed the new blower resistor and positioned the new and old harnesses for splicing and wire transfer.
Since I had already determined that the over use of the high blower speed was the cause of all of this trouble, I only replaced the red wire because it had been burnt. The orange wire because it had melted plastic in it and the black wire because it carries all of the blower system ground load. The other three wires were undamaged and transferred to the new connector to make a neater repair. This is what I do and do not recommend the inexperienced to do the same.
I finished the job, started the engine and turned on the a/c. Now the whole picture becomes clear. The compressor was short cycling from a low refrigerant charge. This vehicle nearly burnt to the ground because the owner would not fix the air condition system.
The air flow was restricted due to leaves blocking the evaporator core fins.
The compressor was short cycling because of a low refrigerant charge.
The owner kept the blower speed set on high all of the time trying to get just a little bit of cool air.
The red wire terminal overheated along with the blower resistor board, which had a leaf or two on it that ignited and slightly burnt the case. Luckily it when out before the rest of the leaves caught on fire.
The customer knew that the a/c had not been working correctly for a few years and had started parking the van under a tree to keep it cooler when parked. That way it would cool down reasonably well for his comfort.
So in the end the leaf build up, the damaged blower resistor, the burnt evaporator case, the damaged harness connector and subsequent fire were due to air conditioning system and vehicle neglect.
One thing that the general population is not aware of is that vehicle blower systems are not designed to be run on high or any speed all of the time. If the refrigerant and heater systems are working correctly the blower speed will need to be adjusted down and back up again to keep the passengers comfortable.
My rule of thumb is to never keep a manual blower system on one speed for more than thirty minutes. Especially the higher speeds. That is only true if the rest of the system is working normally. If it is not, no more than ten minutes on any speed. Wait at least five minutes before returning to the same speed.