Voltage good one minute: gone the next

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Voltage good one minute: gone the next

September 14, 2017, 03:35:43 pm

Newby here and I thought I test the collective wisdom of the group. I am preparing to pick up a 1992 U280 (new to me) and the PO was doing some testing on it. It hadn't been run in a while so coach batteries didn't have enough power to start it. He opened Boost and it started right up. (8.3L Cummins) While it was running he did a scan of engine instruments and all were fine. Voltage indicated 14.2 V. After a few minutes voltage dropped to 0. He shut it down and did no further troubleshooting.

While thinking about what could have happened, I began to wonder if FT placed a fusible link in charging system to prevent overload of alternator.

I haven't seen one in any of the electrical diagrams on other FT coaches. I have several other ideas to pursue but would like info on fusible link, if there is one. Since it has been setting for some months, I will be looking at main ground corrosion and then working on in from there.

Thanks,

jk

Re: Voltage good one minute: gone the next

Reply #1 – September 14, 2017, 03:59:37 pm

May only be an intermittent gauge, or wire or connector. Measure voltage at the battery.

Re: Voltage good one minute: gone the next

Reply #2 – September 14, 2017, 04:25:21 pm

Check voltage and charge and then check the engine batteries if low. Pull connections and clean. Buy an inexpensive digital voltmeter to keep with you. It hadn't been run for a while probably means a long while. Lots of time for corrosion to work on the battery terminals/connector.

"He shut it down and did no further troubleshooting" seems a bit strange to me. How are you supposed to get it home? It's up to you to put the pressure on him/her.

Pierce

Re: Voltage good one minute: gone the next

Reply #3 – September 14, 2017, 05:10:31 pm

Flip up the dash lid. On driver's side is the IGNITION SOLENOID, Check voltage there-- one large lug connected to the chassis battery, so it should read chassis battery voltage all the time (yes, unless you have a connection issue). Other large lug should have the same voltage (and supply dash gauges and everything else that only works with the ignition on) when the key is ON.

Both your dash gauge and this solenoid are within 2' of each other, so easy to compare readings.

Let us know what you find.

Re: Voltage good one minute: gone the next

Reply #4 – September 14, 2017, 05:45:27 pm

Quote from: kimosabe99 – September 14, 2017, 03:35:43 pm

I began to wonder if FT placed a fusible link in charging system to prevent overload of alternator.

Hey JK,

Welcome to the Forum! Sorry you're having a problem, but this is very common when picking up a coach that may have had less than stellar care.

To answer your question, I have never heard of Foretravel using a fusible link in any circuit. The electrical circuits on the U280 are all protected by either fuses or circuit breakers. Most of the fuses are found downstream of the ignition solenoid. Some of the circuit breakers are auto reset - some require a push of a button to reset.

To do any kind of electrical trouble shooting, you will need a couple of wiring diagrams - one is labeled B-2037, the other is B-2126. Try to look through the books and paperwork that come with the coach to see if these are available.

Re: Voltage good one minute: gone the next

Reply #5 – September 14, 2017, 05:57:35 pm

JK,

If you can't find any or all of the U280 electrical schematics in your manuals or here, I have all of them and can upload or email.

Pierce

Re: Voltage good one minute: gone the next

Reply #6 – September 14, 2017, 07:45:59 pm

Quote from: Pierce & Gaylie Stewart – September 14, 2017, 05:57:35 pm

JK,

If you can't find any or all of the U280 electrical schematics in your manuals or here, I have all of them and can upload or email.

Pierce

Pierce,

Have you participated in this project yet?

Coach information preservation

Once and done

Re: Voltage good one minute: gone the next

Reply #7 – September 14, 2017, 07:59:02 pm

I possibly have some good news for you. On MY 280 once the engine starts it will keep running even if the ignition solenoid stops working. To tell if the solenoid fails, ALL gauges will stop working. A tap on the solenoid with the end of a metal flashlight got my gauges working again. Perhaps it's this simple. Then again.....it IS a Foretravel.

Re: Voltage good one minute: gone the next

Reply #8 – September 14, 2017, 08:18:01 pm

"Then again.....it IS a Foretravel." A Foretravel is very well documented compared to most others.

Re: Voltage good one minute: gone the next

Reply #9 – September 14, 2017, 09:19:31 pm

Check all of the mentioned stuff first. The odds of the batteries actually going from 12 plus to zero immediately is almost none. Test ignition solenoid this check batteryconnections including where the copper lug is crimped on the battery cable itself.

Re: Voltage good one minute: gone the next

Reply #10 – September 14, 2017, 09:51:07 pm

Quote from: kimosabe99 – September 14, 2017, 03:35:43 pm

While it was running he did a scan of engine instruments and all were fine. Voltage indicated 14.2 V. After a few minutes voltage dropped to 0. He shut it down and did no further troubleshooting.

Did he notice any of the other gauges AFTER the voltage dropped to 0?
If he panicked and shut down without noticing the other gauges at the time? They could have dropped also.
IF so it sounds like the ignition solenoid, ours has done the same thing, a tap on the ign. sol. will usually get you by until you can get to the next NAPA store. WE did...........

Re: Voltage good one minute: gone the next

Reply #11 – September 14, 2017, 10:16:39 pm

the 14.2 volts would likely be the alternator output reading while running on the Boost house battery. When the boost dropped out the voltage input to the alternator stopped and the alternator voltage cascaded down to zero. So maybe the start battery is dead, shorted, or open, or the ignition circuit is open. The diesel might run without electric power.

wantabe

Re: Voltage good one minute: gone the next

Reply #12 – September 25, 2017, 11:05:33 pm

Down on location now. No more remote diagnostics. Coach has 3 - 8D 1450 CCA Batteries in it. The left (most forward) battery is chassis battery. First test indicated 11.64V. Other two are at 13.6 or so and seem ok. Dash solenoid is working. Gauges functioning. Alternator has significant rust and corrosion on lugs. Planning on slow charge of chassis battery and see what she does. Plus cleaning up alternator and testing it. If battery needs replacement, I'll be renting a forklift.(*&^*(^) or trying a different battery combo like two Group 34's at 850 CCA

Re: Voltage good one minute: gone the next

Reply #13 – September 26, 2017, 10:40:41 am

These have been used to replace batteries. If you don't want to rent something. They are handy for other things also.
1500 lb. Capacity ATV/Motorcycle Lift

Re: Voltage good one minute: gone the next

Reply #14 – September 26, 2017, 11:06:55 am

Quote from: kimosabe99 – September 25, 2017, 11:05:33 pm

If battery needs replacement, I'll be renting a forklift...

Jack,

No need to strain your back! Several Forum members (myself included) have taken advantage of the helpful employees at their local O'Reilly auto parts stores. If you buy one (or more) of their 8D batteries, and run your coach by the store, they will swap out the batteries for you! The price on their AGM8D Super Start battery is very competitive, and the batteries (made by East Penn) have a good reputation around here.

https://www.oreillyauto.com/detail/super-start-fleet---heavy-duty-5000/marine-parts---accessories-16900/deep-cycle---marine-batteries-17354/battery/agm8d/4742645

Re: Voltage good one minute: gone the next

Reply #15 – September 26, 2017, 03:30:41 pm

The latest: put a slow charge on chassis battery to just over 12V, reconnected cables. It had enough ass to start the 8.3 without the boost. Unfortunately, alternator did not show a charge at all, both at the dash and direct measure at the battery. I went back up and thought I'd try setting up idle and then measuring right at alternator. Alternator did not kick in with foot throttle. As soon as cruise control was turned on and engaged at 1200 RPM, VOILA!! Volts at dash were 14.1 - 14.3V. Verified this at battery also. When cruise is disengaged, it stops charging. This is peculiar. Does this sound like an excite problem?

I intend to go ahead and replace suspect battery and then fix some other things and come back to wiring. Here are some pix.

jk

Re: Voltage good one minute: gone the next

Reply #16 – September 26, 2017, 05:05:20 pm

charging the chasis battery to just over 12 volts is still barely 50-60% charged. A full charge should be around 12.8 for a GEL and higher for other types. At low idle, your alternator may be charging but not enough to register. Also depends on what type of alternator you have. most Leece Nevilles will cut in at low idle but will not output alot of amps. other alternators will cut in at a higher RPM.

Re: Voltage good one minute: gone the next

Reply #17 – September 26, 2017, 05:45:49 pm

Ours at full charge: ( with some power on, as usual)

Re: Voltage good one minute: gone the next

Reply #18 – September 26, 2017, 06:22:37 pm

JK,

We have had many members on this Forum with alternator problems. If the alternator on this coach has ever been replaced, worked on, or fiddled with by mechanics unfamiliar with RV battery isolator setups, there is a good chance it could be incorrectly wired. You will need to look closely at the back of the alternator, count the number of small wires, and try to figure out where they are connected. A good clear photo of the back of the alternator would be helpful. Once we know what type alternator you are dealing with, we can possibly make some suggestions to correct the operation.

Meanwhile, you could search the terms "sense wire" and "excite wire" on the forum, and read posts to get up to speed on some of the possible problem areas. You will get many hits to your search.

Re: Voltage good one minute: gone the next

Reply #19 – September 27, 2017, 11:20:48 pm

First. Thanks for all the helpful replies. Installed a new chassis battery and starting issues are gone. Still using the cruise on/off switch to excite the alternator. It is a four pole, brand unknown but I am pretty sure it is not a leece Neville. Charging is now in the 13.6 - 13.8V range. Tires check out good, Michelins that are about 8 years old, less than 1000 miles and always properly inflated and covered. Shake down trip scheduled for tomorrow. 1076 miles. Back to where I have access to big truck shop. Yippee!!!
jk

Re: Voltage good one minute: gone the next

Reply #20 – September 28, 2017, 08:00:42 am

Quote from: kimosabe99 – September 27, 2017, 11:20:48 pm

Still using the cruise on/off switch to excite the alternator. It is a four pole, brand unknown but I am pretty sure it is not a leece Neville.
jk

Just a suggestion, but it should not be difficult to troubleshoot this (having to use cruise to power the excite terminal). It is probably as simple as someone tapping into a cruise control wire instead of one of the many "ignition hot" wires in the engine room.

Re: Voltage good one minute: gone the next

Reply #21 – September 30, 2017, 04:22:36 pm

"Tires check out good, Michelins that are about 8 years old, less than 1000 miles and always properly inflated and covered."

There will be lot's of opinions on 8 year old tires regardless of care. One blowout can cause very expensive repairs. For me, I would budget for new tires.

Re: Voltage good one minute: gone the next

Reply #22 – October 01, 2017, 06:27:39 am

I'd have a Michelin dealer check them out and plan to change them at 10 years if they check out good.

Re: Voltage good one minute: gone the next

Reply #23 – October 01, 2017, 11:52:25 am

Quote from: amos.harrison – October 01, 2017, 06:27:39 am

I'd have a Michelin dealer check them out and plan to change them at 10 years if they check out good.

I made a run from Pensacola to near Buffalo the other day. Tires had been regularly treated with 303 and were covered with white covers. It was plenty hot (90+) day one. Tires performed fine with some definite blooming appearing. I found a tech bulletin from Michelin which I will go by on appraising future tire life. You probably have seen it. www.michelintruck.com/assets/pdf/bulletins/TB_Service_Life_RV_Tires.pdf

Main problem on trip was shedding a hydraulic fan pump belt. I nursed it in to Russell Truck Service, 125 West Blvd, Montgomery, AL. This is an independent shop and I recommend it highly. Replaced belt, put in a new inline filter in Isuzu generator motor (on this coach it is immediately before 12V fuel pump) and out the door for $114.00 This week I will be checking out the tensioners etc. to see why belt failed. I'll throw out this tip. When belt is in trouble, a easily visible area of black soot will appear on the white grill.

jk

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