05-06-2012, 04:57 PM
Join Date: Jul 2011
AMD FB1-4001 motor failure
The AMD FB1-4001 motor in our Chevy S-10 conversion has developed a serious problem. Since the installation of the motor in August 2011, the truck has been driven about 300 miles at low and medium speeds. All seemed fine until yesterday it suddenly began to lose power and then stopped entirely. After it was towed in I did some troubleshooting and found that the motor would not turn unloaded with 12v applied.
I pulled the headband off and observed that the outer set of brushes (closest to the end of the motor) were all perched up in their holders with the springs pressing against their sides (holding them up off the commutator). The inner set of brushes were seated normally but all showed signs of discoloration where the braided wires meet the carbon block, and on one of them the wires were burned completely off the carbon block! That brush's spring is also damaged from heat.
I seated the outer brushes down into their holders with the springs on top and now the motor turned with 12v applied, but it made a lot more noise that before. I rotated the shaft by hand while watching the commutator surface - at one point there is a shiny wedge of something thin (insulation sheet) coming out from between two of the metal contact strips - I believe that's what is making the noise as the outer brushes ride over it.
I've posted photos of my project on Flickr. The last few photos show the motor damage.
As I mentioned, the overheating seems to be concentrated on the rear brushes.
My guess as to the sequence of events would be:
1. While driving the strange thing (marked in the top brushes photo) comes out from between two bars on the commutator.
2. The now-irregular surface makes the front brushes bounce up and get stuck with their springs on their sides.
3. The rear brushes now have to carry all the current and they overheat until all are stressed and one completely fails.
The motor dealer and manufacturer are so far unwilling to accept this sequence of events. They keep coming back to the idea that the motor has been abused or overloaded. They offer to "look at it" - but that involves removing it from the truck and shipping it back to them at my cost (~$150). I asked the dealer for a candid assessment of the chances of getting a warranty repair or replacement and he said it was a crap shoot.
I disagree - what do you think?
This is a very ordinary S10 conversion using components called out in many parts lists. The controller is a Curtis 1231C. The power source is a set of 24 Trojan T-125 6v batteries for 144v total. My simplified schematic is also posted in the Flickr set.
The driving has been on both town and country roads at speeds 25-50 MPH. The day that the motor stranded me I'd been driving 15 minutes at about 30-40 MPH, then stopped at the hardware store for about ten minutes, then headed back to the office at somewhat higher speed (different road max 50 MPH) for about 10 minutes when it died. I've driven the truck on that same errand routine at least 6 six or eight times without any issues.
The tires are the stock P215/75R15 and inflated to the sidewall pressure, so they are 27 inches in diameter. The rear-end is the stock unit with a gear ratio of 3.73. The transmission is the stock manual five-speed "New Venture" NV1500 unit . Gear ratios in the NV1500 are 3.94, 2.37, 1.49, 1.00, and 0.830. An online RPM calculator shows that at the time of the failure the motor would have been turning at 3320 rpm - that seems pretty normal. And the truck was carrying no cargo so there was no load beyond the weight of the converted vehicle.
Thanks guys for any insights you can provide... if I am doing something wrong, I need to learn how to avoid it in the future. And if I am not, then I've learned that the motor manufacturer's warranty is not worth much.