Slow engine cranking

[Rikadoo]

Hey i have read old posts, an actually found similar posts, however the results were so tremendous i thought bringing this to the group was warranted. 
Customer brought there 2005 coach with a Cat engine to us to address severel issues, one of them being seems slow when cranking, they had been elsewhere where they were sold 2 new batteries. The result was the same, two fully charged batteries yielded what appeared to either be a starter or engine issue as it would engauge then struggle to crank over, but it would always start, so i had suspected possable Voltage drops mainly due to the visual cues i was seeing, after just one VD check of 4 volts accross the battery switch, i made the decision to clean all the connections, and replace the battery switch. The tool that helps with this the most is a angle drill with a small abrasive pad, disconnecting the batterys i started with them, to the frame where they had two different attaching points, on to the starter, cleaned both the ground and the positive connections, i replaced all the lock washers on every connection, and applied electrical grease on every spot as i was reassembling. As for the battery switch of course we recieved the wrong parts (my fault) so till we get the replacement part i reassembled it in case we had to move it. So rechecking for voltage drop at the same spot went from 4 volts to 1, however the results with that are amazing, the difference in the cranking performance are day an night, dont get me wrong it is nowhere near that of a gear reduction style starter, but it is all of what these old style starters could do in there prime. To be sure im positve that due to the extreamly low cranking amps that caused this starter to slow down may have accelerated the wear on the brushes and may be a problem down the road. But just knowing how with age and the derogation of connections that electrical performance can be effected. I bet with after preparing to do the job i had MAYBE 1 hour in removing an cleaning all the high amp connections. Also as you see the solinoid at the starter, when i was bidding the job i said i “would not” be removing the reverse torx bolt for fear it would snap, so you can tell that too has its issues, but for the damage that im sure the starter has endured had i not recieved the results i was aiming for the next step would have been to replace the entire starter, which i will still propose to the customer. For the battery switch i remained with the mfg. Cole Hersee which is still available on line, that in my haste of finding the proper wire configuration i failed to note the post size, i needed 1/2 inch an bought 3/8🤦‍♂️ “i was sooo close😂” 

[jacwjames]

Wow, lots of rust, no wonder there are voltage problems.  Wonder where the coach has spend most of it's life?

Keep us posted, always interesting to see how different problems are solved.

[TomV48]

Ditto.   Good luck

[Frank McElroy]

12 hours ago, Rikadoo said:

Hey i have read old posts, an actually found similar posts, however the results were so tremendous i thought bringing this to the group was warranted. 
Customer brought there 2005 coach with a Cat engine to us to address severel issues, one of them being seems slow when cranking, they had been elsewhere where they were sold 2 new batteries. The result was the same, two fully charged batteries yielded what appeared to either be a starter or engine issue as it would engauge then struggle to crank over, but it would always start, so i had suspected possable Voltage drops mainly due to the visual cues i was seeing, after just one VD check of 4 volts accross the battery switch, i made the decision to clean all the connections, and replace the battery switch. The tool that helps with this the most is a angle drill with a small abrasive pad, disconnecting the batterys i started with them, to the frame where they had two different attaching points, on to the starter, cleaned both the ground and the positive connections, i replaced all the lock washers on every connection, and applied electrical grease on every spot as i was reassembling. As for the battery switch of course we recieved the wrong parts (my fault) so till we get the replacement part i reassembled it in case we had to move it. So rechecking for voltage drop at the same spot went from 4 volts to 1, however the results with that are amazing, the difference in the cranking performance are day an night, dont get me wrong it is nowhere near that of a gear reduction style starter, but it is all of what these old style starters could do in there prime. To be sure im positve that due to the extreamly low cranking amps that caused this starter to slow down may have accelerated the wear on the brushes and may be a problem down the road. But just knowing how with age and the derogation of connections that electrical performance can be effected. I bet with after preparing to do the job i had MAYBE 1 hour in removing an cleaning all the high amp connections. Also as you see the solinoid at the starter, when i was bidding the job i said i “would not” be removing the reverse torx bolt for fear it would snap, so you can tell that too has its issues, but for the damage that im sure the starter has endured had i not recieved the results i was aiming for the next step would have been to replace the entire starter, which i will still propose to the customer. For the battery switch i remained with the mfg. Cole Hersee which is still available on line, that in my haste of finding the proper wire configuration i failed to note the post size, i needed 1/2 inch an bought 3/8🤦‍♂️ “i was sooo close😂” 

Good job.  Checking for voltage drop is something that should be top on the trouble shooting priority list vs just assuming weak batteries or a bad starter.  Years ago, I ran across a similar slow crank condition only to fund a corroded ground cable on the engine block causing the engine block to be at about 3 volts vs ground.  So, the slow cranking starter was only seeing about 9 volts.

[Rikadoo]

So just a follow up as how the job turned out, i replaced the battery switch, we urged the importance of replacing the starter due to the past operating conditions it has undergone. There choise was to continue on with out replacing the starter, so after all the other non related work was compleated they drove off. 
Its funney how the work flow happens, my next job was a electrical challange too.

So at this point the original post of slo crank is concluded, i add this next story not to confuse but merely to reinforce the importance of trust but verify!

I had a Diyr bring me his 1995 gasser moho that he stated has electrical gremlins, coach batteries went dead after short while of use, genny would only turn over once the main engine was running, steps, lights, water heater were all intermintent, he replaced the batteries, he just couldent get on top of it… So now as im looking over stuff it all looked fairly normal, Measuring coach battery volts with the engine running was 12.8 while the chassis battery was only 13.0, yet if i went to the battery isolator it was showed 14.6??? So the fact of this coach was 29 years old kept running thru my head, i found on the chassis battery the universal battery ends were 💩💩, that upgrading them brought the chassis battery up to 14.5 yet all the other issues remained. When measuring the voltages at 1st i connected my dvom to the chassis battery, then because of proximity i would slide my positive lead over to the coach batteries, now the positive lead there was reading 14.2 with the engine running??? So i did a voltage drop on the genny with the main engine off 10volt loss on the ground, i went back to the coach batteries, what i thought was a couple of frame grounds were the 2/0 cable for the inverter was ONLY for the inverter and not connected to the frame, then peeling back the new plastic conduit on the other ground wire showed a couple 10 ga wires going to a “old buss bar connector” that went somewhere i supposed to the inside of the coach, but ultamatly there was NO ground to the frame nor was there any evidence that there had ever been one. So i made a custom cable and grounded the coach batteries! Now it was a whole new coach, the genny cranked right up, all the utilitys were happy an consistent! Again it seems my lesson is to always verify the integrity of the basics and dont assume anything.