02/28/2026
I wish I had the time to do a whole class on this troubleshooting case study.......but I just had to happen at 1:30 on a Friday afternoon😠😠
The story: A student brought their 08 F150 in to repair a broken serpentine belt. Pretty straightforward ....get the utility knife out, cut the belt wrapped around the fan clutch (remember this for later), remove the shroud, fan clutch, and replace the tensioner.
The students get it back together and it runs like P**P. Hmmmm. Go to check codes and 11 codes the return immediately. Hmmmmm. At Diesel Tech we are pretty unlucky .......but not that unlucky.
Thankfully the student paid attention and verified that it was about 15 minutes after he realized the belt was failing this symptom happened.
Now, do we attack codes, run in circles and panic or quit for the day?
Take a breath, and think what happened recently that could affect so much. Hmmmm, that belt wrapped around the electronic viscous fan clutch seems suspicious. Also a common power supply or grounding issue will typically cause that many codes at once.
A quick trip to All data and a wiring schematic shows a power supply to the viscous fan. Following it back, we see numerous in harness splices going off to the many components we have codes for.
Replace the 15 amp .......bingo and the student is off to enjoy their weekend.
Electrical is hard to teach, but hopefully examples like this can help people to take time to think BEFORE panicking 🙂
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