1995 U300 dropped to 8 1/2 while driving?

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1995 U300 dropped to 8 1/2 while driving?

June 26, 2020, 09:53:01 am

We were headed to PA for the weekend to camp yesterday. We got off at a rest area and when we got back on the interstate the charging needle dropped to 8 1/2.
My husband thought maybe we broke a belt so we got off at next exit and headed back to Ohio.
Just after the state line we got off at an exit that had truck stops and pulled into a lot trucks used to go get fast food.
He got out to check the belts and when he got back in to restart it, it wouldn't start. We did manage to start the generator before we got off.
Called coach net and the called a tow company and found a place to look at it only a mile away.
We got it started again and tow truck escorted us to the shop.
Shop determined no belts are off, alternator is good, batteries are good.
They are still looking at it today.
I was wondering if anyone has had a similar experience and if could be electronic. Also the transmission temp light came on and it was only 150 degrees.
Thanks, Susan

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #1 – June 26, 2020, 09:58:38 am

We have had the experience of the alternator failing. We just start the generator, turn on the boost, and keep on going. You can cross the country that way if everything is working like it is supposed to.

You didn't mention the isolator. All the power from the alternator goes through it.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #2 – June 26, 2020, 10:07:27 am

Thanks we will tell them about the isolator. I know when he turns the boost on it doesn't light up so we don't know if that's working or not.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #3 – June 26, 2020, 10:19:38 am

Rick has stated (above) the standard procedure for suspected alternator failure. Has saved many members from grief.

The transmission temp light MIGHT be due to low start battery voltage. Running engine with low battery voltage can cause all kinds of weird symptoms. Not good for the transmission in general - messes with the critical electronics.

Hopefully the shop is familiar with the DUVAC alternator + diode isolator + dual battery bank charging system. It should be a simple matter to trace the charging circuit from alternator to isolator to batteries. A break anywhere in that chain would cause the symptoms you describe.

The simple diagram below might help them understand your charging system.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #4 – June 26, 2020, 10:23:41 am

Just basic diagnostic for any tech with knowledge of DUVAC alternator and diode-based isolator.

First step is to determine whether this is a gauge reading issue or alternator/isolator/battery issue.

When the gauge reads below 12 VDC, what is the reading at the chassis battery? Center and outer lugs of battery isolator?

And, there are several good "work arounds" you would do before resorting to being towed. You can drive cross country with an alternator putting out ZERO with generator on, boost on.

And, please put what coach (year and model) in your signature or at least the post so we don't have to wonder. Thanks.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #5 – June 26, 2020, 10:35:30 am

We are unsure if the boost is working. It is a 1995 U300 we bought in Ca. Drove it all the way home to Ohio in Feb with no problems. At first generator wouldn't come on it kept dropping out. I forwarded the charging diagram to the shop.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #6 – June 26, 2020, 10:39:08 am

Quote from: Rocky1down – June 26, 2020, 10:35:30 am

We are unsure if the boost is working. It is a 1995 U300 we bought in Ca. Drove it all the way home to Ohio in Feb with no problems. At first generator wouldn't come on it kept dropping out. I forwarded the charging diagram to the shop.

If boost is not working, EASY to short-term fix. Just remove the battery cable from one of the boost solenoid's large lugs and ADD it to the other. This will allow the converter or inverter/charger to charge both battery banks.

Of course of no generator or shore power, it will also allow both banks to DIScharge together, so may want to separate them if dry camping. Remember, both cables are HOT/connected to a battery bank, so don't let them touch any chassis metal.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #7 – June 26, 2020, 10:52:24 am

We didn't have to have it towed. We sat a couple hours with generator running so it started on its own. Tow truck driver just drove behind us to the shop.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #8 – June 26, 2020, 11:15:39 am

Quote from: Rocky1down – June 26, 2020, 10:52:24 am

We sat a couple hours with generator running so it started on its own.

If the generator was able to recharge the depleted start battery bank, then your boost solenoid did close.

The light bulb in the boost switch may be burned out.

Again - simple tests with a multimeter can confirm operation of boost solenoid.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #9 – June 26, 2020, 12:49:01 pm

Hope you have good luck finding your issues while on the road.

Because of the age of our coach I proactively replaced the starter, alternator(rebuild then replace) and then the isolator with a Blue Seas battery combiner and added 340 watts of solar to keep everything charged while in storage.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #10 – June 26, 2020, 01:12:51 pm

We were close enough to home to drive our Jeep back home. We unloaded our clothes and food and brought it back home.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #11 – June 26, 2020, 03:01:49 pm

Don't let that mechanic start changing parts without someone on here approving of what they are doing. Apparently they know about diesel trucks but not Foretravel (or any coach.). They can really mess things up where a simple repair will have you back going.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #12 – June 26, 2020, 07:10:49 pm

Quote from: Rocky1down – June 26, 2020, 09:53:01 am

We got it started again and tow truck escorted us to the shop.
Shop determined no belts are off, alternator is good, batteries are good.
They are still looking at it today.

Thanks, Susan

If " The Shop" knows how to use a multimeter and interpret the readings, the shop can quickly check the flow of electrons through the battery isolator to the battery.

FWIW, there will be a measurable voltage over a bad connection when power is trying to be drawn through the connection. The higher the voltage the worse the connection.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #13 – June 26, 2020, 09:21:52 pm

Hi Susan and Bob, I am here in Aurora, Ohio close to you. I have a 1994 U300 and have had similar problems. If you would like to give me a call I may be able to help. It is about 9:15pm Friday now, so if you want please call anytime after 7am tomorrow morning Saturday.

sorry here is my number
330.802.5201

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #14 – June 27, 2020, 07:22:07 am

Couple years ago, I had the same issue - Low voltage... turned out to be a loose ground at the frame. Cleaned and tight, over 30k miles since

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #15 – July 01, 2020, 02:16:27 pm

Sorry I haven't posted back. The shop thinks an isolator is bad. They are not having any luck finding one.
They called Foretravel this morning and are waiting on a call back.
I called Foretravel last Thursday when it happened and still haven't got a call back.
Does anyone know if the isolators are still available?
Thanks, Susan

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #16 – July 01, 2020, 03:01:49 pm

Yes, diode-based isolators are still available-- certainly not a Foretravel-specific item.

But other work arounds:

Battery combiner

Manual marine ON-OFF switch with alternator B+ and chassis battery to one lug and house battery to the other.

And, of course short term work around is to combine wires from B+, chassis and house battery on one lug. Be sure alternator sense wire is also to any location directly connected to the chassis battery.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #17 – July 01, 2020, 03:33:37 pm

Quote from: Rocky1down – July 01, 2020, 02:16:27 pm

Does anyone know if the isolators are still available?

Susan,

As Brett says, you have several options if you want to (or need to) replace the OEM battery isolator on your coach. A quick search of this Forum will provide many threads related to this subject, and many opinions about the "best" solution.

IF you desire to retain the original reliable, time-proven factory design and simply replace the isolator with a similar bolt-in component, then I would recommend the item linked below.

The Victron ArgoFET 200A 2-battery isolator is functionally the same as your OEM isolator, but it also has improved the design in a couple ways. First, it has virtually no voltage loss between the alternator post and the battery posts. Second, it has a dedicated alternator energizing input that will allow great flexibility in choice of (future) replacement alternator brand and model.

Victron Argofet Battery Isolator

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #18 – July 01, 2020, 05:44:40 pm

If you hook up the 3 cables on the isolator together you can keep going and at night disconnect them so you engine battery won't
get discharged. Google battery isolator and you will find them.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #19 – July 01, 2020, 06:05:14 pm

Will the Victron work with multiple batteries?
Ours has 4 house batteries and 3 start batteries.
Thanks, Susan

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #20 – July 01, 2020, 06:08:18 pm

Quote from: Rocky1down – July 01, 2020, 06:05:14 pm

Will the Victron work with multiple batteries?
Ours has 4 house batteries and 3 start batteries.
Thanks, Susan

Actually you have ONE house battery made up of 4 individual batteries and ONE chassis battery made up of 3 individual batteries.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #21 – July 01, 2020, 06:25:40 pm

Quote from: Chuck & Jeannie – July 01, 2020, 03:33:37 pm

Susan,

The Victron ArgoFET 200A 2-battery isolator is functionally the same as your OEM isolator, but it also has improved the design in a couple ways.

Victron Argofet Battery Isolator

Chuck,
What size would be needed 100A or 200A?
John M.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #22 – July 01, 2020, 06:54:49 pm

Brett,
If you install a Perko manual switch instead of the isolator, is there a need for the boost solenoid?
John M.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #23 – July 01, 2020, 07:05:05 pm

The boost switch would be redundant (and automatic from the driver's seat). The manual switch on ON is exactly the same as a boost switch and solenoid being ON.

Re: 1995 U300 dropped to 8 1/2 while driving?

Reply #24 – July 01, 2020, 07:06:18 pm

No, takes possible failure out of the equation. Just have to manually do it. Turn Perko switch to both.

P

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