Community Forums

Mutt · 07-28-2018, 09:17 PM

My 8.3 ISC suddenly decided to lose all power as I was rolling down the exit ramp. Fortunately, I was just feet from a stop light when I realized the loss of power. Everything was dead. No dash lights...and I didn't get any warning lights before it died. As I was gathering my thoughts together and had gotten the Tech guy from FMCA's new roadside service on the phone, I decided to check the battery cables which were in tact, then upon turning the battery disconnect off and back on, I got dash lights and was able to restart the engine. The Tech Service Guy was not able to suggest any possibilities except maybe a ground wire somewhere. In addition, he was of the opinion that the burp /loss of power probably shut the ECM down and therefore it probably didn't grab any Codes.

In any event, I have driven about 200 miles W/O further incident. But, my question to you is....has anyone experienced anything like this during there travels? And is there a Sensor anywhere that could "Fault" and kill the ECM and all power from the Batteries? The Battery disconnect switch seems to be in good working order, so I don't think that is the problem. Any Ideas?

broadrun · 07-29-2018, 06:36 AM

Have you done any recent work on the battery connections? I know you said that you checked them but I just thought I'd ask...

I've got a 2001 HR with an 8.3 and am very interested to find out of you ever solve this as it could happen to me someday.

twinboat · 07-29-2018, 06:44 AM

My first thought would be the disconnect itself. Possibly the cable connections on it.

Is it a manual switch, a 12 volt powered continunious duty solenoid operated by a remote switch , or a latching relay, controlled remotly ?

BigLar368 · 07-29-2018, 06:54 AM

Only thing I figure it would be was a loose connection or bad ground also loose. Lots of them are powered straight off the starter's main cable. I would check all of the connections you can get to. I have seen battery cables hooked up good and tight only to find the slightest amount of corrosion cause problems. Hope ya find/. Best of luck.

Dsallach · 07-29-2018, 07:04 AM

If your coach is like mine, the battery disconnect you are talking about is the big red manual rotary kind. From your symptoms I would suspect the contacts in the rotary switch are corroded or burned. While going down the interstate your alternator is producing power. As you decelerated the alternator cut out causing a drop in amperage. When you turned the switch the contacts made better contact. I have had a switch like that fail. The switch outwardly looked perfect.

tomgagne · 07-29-2018, 07:22 AM

I had a similar problem and it was the ignition switch. My issue would be that the coach would start, run a bit and then just die. No warning lights. I would put the key in the shut off position and it would restart as normal. I was able to duplicate the issue by starting the coach, and while running I jiggled the key until it shutdown, again with the same symptoms. It didn't take much jiggling. I replaced the ignition switch (available at Napa) and have not had any additional shutdown problems. With my issue I never had the coach shut down while driving but thought that it could happen.

Mutt · 07-30-2018, 07:46 AM

The alternator spooling down is an interesting item that might cause a potential loss of power, assuming the contacts on the Battery Disconnect Switch are/may not be making good contact. Going to try and take the Switch off today and see what kind of conditions I find.

The comment about the Ignition Switch......, I tried the switch several times as I sat at the stop light, flipping the switch off and on (didn't try and wiggle it though). I didn't get any response from the Switch until after I went outside to the Battery Compartment and turned the Main Battery Disconnect Switch off and back on. Immediately after doing that is when the Ignition Switch lights came on and I was able to restart the coach.(Much to the delight of the Policeman standing in my doorway I might add, since we were blocking traffic.)

Dsallach · 07-30-2018, 08:04 AM

One other thought, when the rig died, did you try holding down the auxiliary start switch on the dash that temporarily ties the house and start batteries together. That should have boosted the amperage. Although if the contacts in the main switch were not making good contact it still might not have helped.

Mutt · 07-30-2018, 08:22 AM

No, I didn't think about it since I had no dash lights. But, since conditions developed as they did, that possibly may have worked. Allow me to beg this question/situation a little further. Is it possible that I may have lost Battery power while on the Interstate(and not realize it), but the Alternator keep supplying needed power....Until I slowed down exiting the Interstate??

Mutt · 07-30-2018, 08:32 AM

By the way... as far as corroded battery cables...I had the cables off the Starting Batteries within the past 3 months testing the Batteries etc., so as far as I can tell those should be making good contact. But one thing is for sure...there is a problem some place. So, I welcome any constructive comments.

Dsallach · 07-30-2018, 08:50 AM

Without seeing your wiring diagram I cannot say for sure but, yes that may be possible.the dash lights would have been off while driving. A basic old diesel only needed power to start. After that it would run on its own until shut down. Yours probably only needs minimal power for the ECM and fuel shut off. With no battery power, When the alternator cut out the fuel shut off solenoid would have closed cutting off the fuel as if you turned off the key. Since the only thing you apparently did that solved the issue was to turn the battery switch, the question would be if the added amperage from the alternator was enough of a boost to power through a failing contact in the battery switch or if the alternator would have back fed the ECM and bypassed that switch somehow. Now that you peaked my interest, When I get home tonight I will look at my schematics. Maybe someone else on this board can answer that in the meantime.
Did the transmission or ECM throw any error codes at all?

Golfer Guy · 07-30-2018, 11:23 AM

Mutt, I have had the exact same thing happen several times! When I finally got it into the shop it was a mystery to my techs. Long story short, I had the tech ride with me on the freeway and by chance it happened. Everything dead. No go.

He pulled out the battery tray and climbed in there behind it (small dude) and tightened a couple battery cable connections coming from behind the battery disconnect switches. What do you know that seemed to do the trick, I have not had that problem for a couple years now.

Another issue is there is a direct wire from the battery to the shift panel transmission pad up front. Supposedly Monaco put a butt splice on that wire a couple feet back from the battery. I have heard that has caused this problem too. It is recommended to replace that butt spice as it can get corroded and lose momentarily connection to the transmission causing complete shutdown.

Take a look at this thread from a couple years ago. Mike Cantor, Gunner, has been a well respected contributor on the forum and explains this better than I do. I haven't seen him lately online and really miss his input, simply brilliant guy.

http://www.irv2.com/forums/f115/rig-...ix-291433.html

Good luck.

Mutt · 07-30-2018, 06:12 PM

I removed the Battery Disconnect Switch, but it appears to be sealed fairly tight. I suppose since these are used in Marine applications they need to be sealed for moisture purposes. Therefore, it might break if I try to open it. All of the cables were tight but I didn't get to the actual contacts. Not sure what that tells me. I might replace it anyway. I will try and trace down some of these other wires/connections and see if I find any loose connections.

Mutt · 08-28-2018, 04:15 PM

Replaced main disconnect switch, but that's not the problem. The problem is with the main control board located below drivers seat. Ignition Relay is drawing/trying to pass, too much current and has damaged the board around the Igntion Relay socket. The Board P/N is 16615059, if anyone has a spare laying around. Monaco no longer supports this Part as I am told by the RV Dealer, that's trying to find a replacement Board. Not sure at this point how long my going is, going to be put on hold. FWIW.