Electrical issue

[052]

I have a M35A2C that I have not had any recent issues until now. A few weeks ago, I went to start the truck and when I turned on the accessory switch, the low air buzzer came on and when I pushed the start button, the truck would not turn over. I turned off the accessory switch then turned it back on and the truck started. When I went to start the truck yesterday I had the same issue, but then the truck would not start. It did not even try to turn over. I thought that it could be the batteries as they were several years old so I replaced the batteries. I turned on the accessory switch, got the low air buzzer then when I pushed the start button, still nothing. I turned off the accessory switch and tried to start again. Now I have no low air buzzer with the accessory switch on. It appears that I now have no power at the accessory switch. I am at 26+v at the batteries. I found some information in the TMs ref not starting and it indicated to check voltage at a few locations. I get no voltage at the locations that I checked. I can't locate any frayed or burnt wires. I do have headlights when they are turned on. I am not sure that I am checking the correct locations for power. I believe that the included pics are the starter relay and wire 74B.

Any assistance is greatly appreciated. Thank you in advance.

 

[glcaines]

I recently had an identical issue with my M35A3. I was convinced that the accessory switch was bad and replaced it. It turned out to be the fusible link. It was erratic - sometimes no problem and then the next time nothing. The fusible link always showed 24 VDC, but would sometimes go open under high amperage.

 

[052]

I recently had an identical issue with my M35A3. I was convinced that the accessory switch was bad and replaced it. It turned out to be the fusible link. It was erratic - sometimes no problem and then the next time nothing. The fusible link always showed 24 VDC, but would sometimes go open under high amperage.

Thanks for the response. Any idea on where to locate them? I know that they can look different depending upon application. I did not see anything that meight be one when I looked at the wiring that I could see.

 

[glcaines]

On my M35A3 they were located on the firewall on the drivers side of the truck. I believe, but am not certain, that on the A2 they are located differently. I had a hard time finding a replacement, but finally found brand new ones from a commercial truck supplier and were a direct replacement.