low volts revisited

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low volts revisited

July 10, 2019, 03:03:58 pm

only getting 12-12.3 volts from chassis battery. replaced isolator, cleaned terminals and islolator connections, batteries are 2.5 yrs old and alternator is also 2-3 yrs old. no change when I plug into shore power but readings is at 13.5-14 with generator running. taking the reading off my silverleaf program so confident the reading is accurate. read the threads from a couple years ago of similar problem but not sure what to do next. thought it was the isolator so put in a new one. kind of frustrating.

Re: low volts revisited

Reply #1 – July 10, 2019, 03:30:51 pm

Dale, There is no charging of the chasis battery when plugged into shore powere on the coach as delivered from Foretravel. Many owners have added chasis battery charging devices to their coaches. Sounds like you might be wanting to do so too.

I am puzzled by charging with the gen and no charging on shore power.

There are a number of solutions availbe to do this, most discussed on this forum. Those discussions can be found by searching the forum.

I use a Battery Tender brand battery maintainer on my chassis batteries. It is plugged in to a 120 vac plug above the batteries on the side of the bed support and connected across by chassis battery bank, ie., positive connection to one battery and negative to the last battery in the bank. I think you may have 2 batteries, so positive on one and negative on the other one.

Hope this helps you.

Re: low volts revisited

Reply #2 – July 10, 2019, 04:07:14 pm

Thanks Rudy. I kind of thought the shore power would not charge the chassis battery but the volts shlould be 13+ running down the road but i am not getting more than 12-12.3 Alternator? what do i test?

Re: low volts revisited

Reply #3 – July 10, 2019, 04:11:10 pm

Alternator, battery isolator or wiring issue (assuming monitors are accurate-- again, digital voltmeter reading at the battery is most accurate).

And checks with the voltmeter at alternator B+ and each terminal of the battery isolator with the engine at 1100 or so RPM will quickly locate the culprit.

Re: low volts revisited

Reply #4 – July 10, 2019, 05:55:56 pm

thanks Brett. Chassis battery on volt meter at the battery is 12-12.3 trying to get a measure off the alternator and get nothing. going to try the isolator and alt-B test. will report back.

Re: low volts revisited

Reply #5 – July 10, 2019, 06:05:03 pm

With engine at 1,100 RPM or so, assuming diode-based BATTERY ISOLATOR, connections good and batteries reasonably charged/not deeply discharged:

B+ alternator to good ground high 13's to low 14's VDC

Center post diode-based battery isolator= same (direct connection).

The outer posts of the diode-based isolator go to the individual banks-- chassis and house. They should read 13.2-14 (.7 VDC lower than center post of isolator).

Re: low volts revisited

Reply #6 – July 10, 2019, 06:12:45 pm

Chassis battery is charged on shore power by onboard charger, starting battery can be charged on shore power by same onboard charger if the boost switch on dash is on. All batteries are charged by alternator. I agree checking the battery condition or charge must be done at the battery. What is the problem, charging system or batteries? What are conditions/loads when getting 12-12.3 vdc? What kind of battery?

Re: low volts revisited

Reply #7 – July 10, 2019, 06:19:10 pm

Mr. Pat, I was referring to the main engine starting batteries as "Chassis Batteries". The other bank of batteries would be the house batteries which are the shore power charged bank.

Hope this helps one know which bank I was referring to. All the best.

Re: low volts revisited

Reply #8 – July 10, 2019, 06:34:51 pm

I have run out of time today so will have to table the project for later. tried to get measure at the alt and isolator but could not get a reading on my voltmeter. I know it works because i got readings off both banks of batteries. either i am not getting a connection or my alt is totally dead. will try again when i have time and stored up a little more patience. Thanks for the responses, this forum is the Best!!

Re: low volts revisited

Reply #9 – July 10, 2019, 06:58:24 pm

Dale,

You state that the alternator is 2-3 years old. So did they install the correct alternator? OEM you had a DUVAC alternator and some shops don't deal with this type of system. So you could have a good alternator that does not know it is supposed to be doing something.

Mike

Re: low volts revisited

Reply #10 – July 10, 2019, 08:23:14 pm

Terminology:

Chassis battery starts the engine.

House battery provides house functions.

Re: low volts revisited

Reply #11 – July 10, 2019, 09:10:44 pm

Take a long wire. Doesn't matter what size, it's a test. Bolt one end to the + connector of the alternator. Attach the other end to the + post of the START (never could understand why anyone would call it a chassis if it STARTS the vehicle) battery. Run the engine and test voltage at the battery. If it's still low, it's the alternator. Btw, if you have the marine type battery terminals you should REPLACE them rather than clean them. That was my problem.

Re: low volts revisited

Reply #12 – July 10, 2019, 09:15:26 pm

Quote from: Twig – July 10, 2019, 09:10:44 pm

Take a long wire. Doesn't matter what size, it's a test. Bolt one end to the + connector of the alternator. Attach the other end to the + post of the START (never could understand why anyone would call it a chassis if it STARTS the vehicle) battery. Run the engine and test voltage at the battery. If it's still low, it's the alternator. Btw, if you have the marine type battery terminals you should REPLACE them rather than clean them. That was my problem.

Actually, it could be little more complicated than that. Remember, most of these alternators are not "simple". This assumes the sense wire and if present the ign terminal have proper connections/readings.

Re: low volts revisited

Reply #13 – July 10, 2019, 09:21:13 pm

Quote from: wolfe10 – July 10, 2019, 09:15:26 pm

Actually, it could be little more complicated than that. Remember, most of these alternators are not "simple". This assumes the sense wire and if present the ign terminal have proper connections/readings.

That's what I just said. Anything other than 13.2'ish is a problem with the alternator. We bypassed everything else.

Re: low volts revisited

Reply #14 – July 12, 2019, 12:46:56 pm

Dale you cannot check the alternator out put at the batteries.. checking at the batteries will give you battery voltage only if alt is not putting out.

Re: low volts revisited

Reply #15 – July 12, 2019, 01:04:15 pm

Quote from: Jerry Steele – July 12, 2019, 12:46:56 pm

Dale you cannot check the alternator out put at the batteries.. checking at the batteries will give you battery voltage only if alt is not putting out.

Actually, checking at the batteries is not an unreasonable initial test:

With shore power off, generator off, engine off, check voltage at the batteries.

Start engine and use cruise control or a second person to raise RPM to around 1,100 and re-check voltage at the batteries.

Let us know what you get.

And, I would check at both house and chassis batteries (in case one side of the diode-based isolator has failed).

Again, exactly the same readings can be had at the outer lugs of the diode-based battery isolator, since they are directly connected to the battery banks by very large gauge wires.

Re: low volts revisited

Reply #16 – August 06, 2019, 03:37:16 pm

Thanks everyone for sharing. Finally got it sorted out, took Cascade Diesel and RV in Northbend Wa to find "Pilot Error". I had replaced the battery isolator, which I am pretty sure was bad and the boost solenoid which I am pretty sure was bad, and I replace the alternator which I am now pretty was just fine. still wasn't getting power from the new alt. so took it off and had it bench tested and it was fine. nor was I getting any response from the new boost sol. Cascade connected an ignition wire to the 4th post on the battery isolator and a ground wire to the boost sol. and all works as it should. I will take some blame for not getting the ignition wire back on the isolator (it was on the chassis battery post on the old one) but the boost sol. did not have a ground wire when I took it off. Anyway my best advise is check, clean and photo the ground connections before you start replacing parts. The upside is I now know how to use a multimeter and a load tester. bought one at Harbor Freight for $20...just before I was about ready to replace my batteries.
Cheers

Re: low volts revisited

Reply #17 – August 06, 2019, 04:06:27 pm

Just remember to use the load tester sparingly,it puts aload on the battery.

Re: low volts revisited

Reply #18 – August 06, 2019, 04:09:14 pm

Quote from: Dale Bernice and Gracie – August 06, 2019, 03:37:16 pm

Cascade connected...a ground wire to the boost sol. and all works as it should.

...the boost sol. did not have a ground wire when I took it off.

Is the new boost solenoid a "4 post" or a "3 post"?

Some boost solenoids ground through the mounting bracket. They have 3 posts (2 large and one small). The small post is the "activation" connection. This type solenoid must obviously be mounted to a unpainted conductive surface that is somehow grounded to the coach frame.

Some boost solenoids require a separate ground wire. They have 4 posts (2 large and 2 small). These can be mounted to any surface. One of the small posts is wired to ground. The other small post is the "activation" connection. It doesn't matter which small post is used for ground - either one works fine.

Re: low volts revisited

Reply #19 – August 06, 2019, 04:25:14 pm

4 post, but it only had one small post wired when I removed it. it is working now but diagram 2126 is not real clear on this part.

Re: low volts revisited

Reply #20 – August 06, 2019, 04:35:29 pm

Quote from: Dale Bernice and Gracie – August 06, 2019, 04:25:14 pm

4 post, but it only had one small post wired when I removed it.

Perhaps that is why it wasn't working. May have been good all the time, but just wired incorrectly.

Easy to test a solenoid. Use a couple jumper wires with alligator clips on the ends. Connect one jumper to a good ground and the other to a known "hot" 12V source. Touch the appropriate spots on the solenoid - it should make a audible noise when it closes (or opens). If you hook your multimeter to the 2 big posts when activating the solenoid, it should show good continuity when the solenoid is activated, and open circuit when the power is removed from the solenoid.

Re: low volts revisited

Reply #21 – August 06, 2019, 06:42:55 pm

Quote from: Dale Bernice and Gracie – August 06, 2019, 03:37:16 pm

still wasn't getting power from the new alt. so took it off and had it bench tested and it was fine. nor was I getting any response from the new boost sol.

I will take some blame for not getting the ignition wire back on the isolator (it was on the chassis battery post on the old one) but the boost sol. did not have a ground wire when I took it off. The upside is I now know how to use a multimeter and a load tester.
Cheers

Congratulations on your success.

Just a few points of order so to speak.

Alternators require battery voltage to start alternating, so some have an "ignition terminal" that gets battery voltage from the ignition switch.

"Boost solenoids" come in two flavors, intermittent and continuous. And 3-terminal or -4.

And finally, just for you, a voltmeter trick. To isolate a bad connection, with current flowing probe for voltage on either side of the connection. No voltage good. Voltage bad. How bad? e=ir

Re: low volts revisited

Reply #22 – August 06, 2019, 07:57:12 pm

Quote from: Old Toolmaker – August 06, 2019, 06:42:55 pm

"Boost solenoids" come in two flavors, intermittent and continuous. And 3-terminal or -4.

Unless you want to go with a solid state solenoid or a latching solenoid (draws no current when in the on position), the 200 amp continuous duty Cole Hersee 24313 is the solenoid of choice and will duplicate the boost and ignition solenoid found in many Foretravels. See lots of them on this page. Amazon.com: 24213 cole hersee

Should be about $35 or so delivered. Don't worry about the small terminals as either one can be hot and the other go to ground. Makes no difference.

Pierce

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