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This may get to be a bit long, but over the past few years I have had a number of Alternators go bad. The thing is they do not really quit. They just cause strange things to happen to my speedometer, cruse control, ECM information and the VMSpc operation. The problems are intermittent. When everything is cool / cold no problem, but as the temperature rises the items listed above take on a mind of there own. We often drive for an extended time. During the night time everything works fine, nice cool air. During the daytime when things heat up everything starts to go South. When I install a new Alternator everything works fine for about 12 to 18 months. This last trip things went bad again, so I stopped and shutdown the engine. Removed the alternator exciter wire. The Alternator is now no more then an expensive pulley. I then started the generator and used the battery charger / Inverter as my power supply for the engine and chassis electrical. Everything worked just fine as we traveled down the road for another 6 hrs. The next morning I reconnected the alternator circuit and started off down the road.Everything worked fine for about 1 to 1 1/2hrs.Then the alternator got hot enough to cause problems. This required the alternator to be disabled again and the use of the generator. The way things act for me are: The speedometer goes nuts, needle jumps from 0 to 50 or 50 to 80+mph. The Tachometer stays right at the set RPM's. When the cruse control is disengaged it will reset, but the system surges and jumps. The ECM check engine light will flash on and off never sets a code. With the Silverleaf running, The alternator over voltage will cause the gauge to jump all over and a warning bell will sound from the software. Also, a clacking(Audio)sound is produced(By the VMSpc-Silverleaf software I use)when the speed signal is corrupted by the noise present on the 12 volt power feeds to the instrument cluster. This also affects other instruments as the noise level on the 12 volt supply circuits increases. I will be installing a Delco alternator, in my case that will have a higher operating temperature and a better cooling system. The price is double the OEM unit, but I have changed out to many not too. Would have saved a lot of money and time had I done this years ago. The Leece- Neville and Bosch units fail but at a much lower rate in my humble opinion,but all will fail in time. So if you have an intermittent issue(S), that as you watch Them happen in regards to temperature, Think alternator / regulator failure due to terminal break down... See my alternator problems photo gallery. 11-6-2014. > Added some additional information and pictures in the gallery section. My thoughts regarding the failure of the alternators in some model coaches when traveling in elevated ambient temperatures. They fail due to the very high temperatures generated from the Exhaust Manifold, Turbo, and to some extent the radiator cooling line location and the Muffler placement on some coaches> due to limited air movement. I built a air duct, that collects exterior ambient temperature air and directs it to the rear of the Alternator; that appears to reduce the temperature of the alternator. I have only run this modification for 6 months, but I went and installed an alternator that would cause excessive noise on the 12 volt output when it got hot and ran it for well over 7,000 miles this past summer with no issues until it finally failed for good. The unit I tested would not work when the ambient temperature exceeded 85deg. F. With the addition of cooler air, this alternator continued to work at ambient temperatures in excess of 95 to 100 degs. The same unit worked very well when the ambient temperatures where below 80degs. and when traveling at night with the add load of all the lights. ( Note! I traveled all the way to the west cost and back with no issues) Now! I did carry a replacement, but it was still in the box when we parked at home. http://community.fmca.com/gallery/album/469-keeping-the-alternator-cool/ I talked to Martin from Silverleaf at the Indy Rally, August(9/2012)and He confirmed my observations of picking up a failing Alternator by the way the software and computer respond to noise being generated in the alternator diodes. Added 9/14/12. Rich. Just Wanted to add a possible item that could cause engine alternator problems. It is a remote possibility that the charger / inverter unit could have an electrical item(s) starting to fail. Primarily the diodes or a capacitor starting to brake down putting an intermittently high load on the alternator output. Look at this link to see if anything sounds familiar. http://community.fmca.com/topic/9148-inverter-on-or-off/#comment-63001