3 Starters in 10 Months???

2014 ProStar, last 8 EN123846, Maxxforce N13, automatic. Key switch, relay, batteries, wiring are all fine. Getting power at starter but won't crank. Now here's the catch...this is an intermittent issue and it always starts and ends the same way. At first, turn the key a couple of times and it will start. Next time it may be 5 to 10 times and it will start, then 10 to 20, 20 to 50 and so on until it just doesn't work at all. Replace starter, get a month or so out of it and the entire process repeats. No mechanic I've been to has been able to diagnose this. I'm hoping one of you has seen or heard of this happening to someone else and can provide some help. Thank you in advance.

 

I have noticed that my volt meter fluctuates between 12 and 14+ pretty regularly. It's never really steady. Unfortunately, electrical issues are not something I know much about. Thank you for the reply.

 

But why the steady decline? New starter works fine for about a month then the whole process begins again. Each starter I've pulled out is fried.

 

If everything I've learned during this nightmare is correct, this model does not have the slave solonoid on the firewall. (2014) Everything I had seen pointed to that as the culprit, only to find my suspect had a watertight alibi: it was never there.

 

Pointing towards alternator/voltage regulator?

 

This to me looks like a missing ground opportunity maybe?