Author Topic: Voltage problem  (Read 7126 times)

Stan Simpson

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Re: Voltage problem
« Reply #15 on: May 21, 2018, 04:14:34 PM »
The journey continues.....Oklahoma City Caterpillar no longer works on motorhomes (coaches).

I ran in to the same problem coming out of Florida a couple of springs ago. The sensor for the boost on the turbo went bad and produced a check engine light. It happened once before, so I knew I could drive okay, just needed to get the sensor replaced. Drove from Jacksonville to Perry, GA trying to find a CAT dealer. There was one outside of Perry, GA, but when I arrived they said they could not diagnose my engine. Had to go to Chattanooga to find one that could connect to the diagnostic port.
Stan Simpson & Becky Glover & Moe the cat
2005 Monterey Laguna IV
C9 400 Cat
Honda CRV toad

Daniel McShane

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Re: Voltage problem
« Reply #16 on: May 21, 2018, 07:48:59 PM »
Update.
I met a guy who stooped to use the dump station who lives nearby. He knew a guy who works on everything. So I got a hold of this guy named John who said he doesn't work on motorhomes. I told him I have plenty of room in mine as I can sit on the engine unlike most diesel pushers. He still was very reluctant, again saying he doesn't work on motorhomes. Again, I told him of the ease of working on mine. He was still trying in a very kind way to say no. I then told him of the other facilities refusing me and practically begging he said he would try and stop by later today. Well about 2 hours later he showed up, I walked him through my situation then he went to his truck, grabbed some tools and went to work. He performed a couple test the other tech did but took some readings at the ECM wire clusters for 2 voltage sources and 2 grounds, not sure which pin numbers. 1 ground seemed curious and led him to believe that the ECM is bad. But now he went a step further, he has several ECM's in his truck. He had one that wasn't exact  but when we tried  it the CAT data ports wnet hot. BINGO bad ECM. He ordered a new one from his supplier in OKC who also "flashes" then with the correct data. I told him I had nothing else to do and if needed I could drive wherever needed, I'd even get him lunch. So now just waiting to hear.

This guy doesn't advertise or selicit work, he doesn't work on motorhomes, has more work than he can handle ( his son gave him a hard time for coming ), and yet he came to help me.  Someone is watching out for me today, Thankyou!!

Hopefully my next post will be on the road.
1999 Monterey Trinidad 30 ft
Cat 3126b
2009 Jeep Wrangler toad

David Handley

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Re: Voltage problem
« Reply #17 on: May 24, 2018, 10:27:48 PM »
Daniel,

I have a 2000 Monterrey, same engine, similar issues.  I would be tickled to know if the ECM fixes your problem.  Please let me know.

Daniel McShane

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Re: Voltage problem
« Reply #18 on: July 20, 2018, 11:55:29 AM »
UPDATE.....Finally back in Tennessee after a few weeks in the Sierra's!! ECM was replaced and coach fired right up but voltage was still high. Replaced alternator and ALL was good. The mechanic asked if I recently had service at a Cat dealer which I did before I left because they downloaded all the necessary info to load into the new ECM. He also noted that the original ECM had been replaced because the existing one was not Cat yellow. Quite an experience and very thankful to all your suggestions and comments and especially John the mechanic who doesn't work on motor homes.




1999 Monterey Trinidad 30 ft
Cat 3126b
2009 Jeep Wrangler toad

Mike Shumack

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Re: Voltage problem
« Reply #19 on: July 20, 2018, 01:18:52 PM »
Drove from Jacksonville to Perry, GA trying to find a CAT dealer. There was one outside of Perry, GA, but when I arrived they said they could not diagnose my engine. Had to go to Chattanooga to find one that could connect to the diagnostic port.

Why couldn't the CAT shop in Perry diagnose? Was it just that they didn't want to work on an RV - or is there some technical reason why they could not hook up to your diagnostic port?  Surely any CAT "dealer/repair shop" has the equipment to connect to the diagnostic port. It's the same port whetehr located in a truck or RV engine.

Dave Atherton

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Re: Voltage problem
« Reply #20 on: July 20, 2018, 04:17:20 PM »
Gentleman,
In most cases there should be one engine diagnostic plug in front and one in the back of the motorhome or in a compartment on passenger side. What I find in many cases is one of the diagnostic plugs will not work and not allow the  technician to connect the Cat ET or Cummins InSite to read diagnostic codes. There are also non-OEM code readers that cannot access the system. Many times the technician will stop if he cannot get a reading from rear diagnostic plug. There is what called a break-out box that connects directly into the J-1 data port on the engine ECM and will override controls in front. It provides a readout the engine ECM data and also will start and run engine to determine if any problem are present. Many engine ECMs are replaced that do not need to be replaced if the tech cannot get a readout from the front or rear ports, without trying the break-out box to determine or verify condition of the ECM. Last point is that low/intermittent voltage can impact the diagnostic codes because many sensors and regulators have a tolerance/margin of only 1/2 volt plus or minus. What happens next is that sensors and regulators that read out of correct operation range are replaced. Problem is often caused by the ground strap on engine ECM not making a good connection.
Dave Atherton Retired Cat Mechanic
« Last Edit: July 20, 2018, 04:47:05 PM by Steve Huber Co-Admin »
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