Had a check engine light and low 10-11 volts. Turned on generator and voltage went up to 12. Vmspc shows 12.5 at idle. Fleet service checked alternator and batteries all checked ok. Thoughts?
With engine running at idle (700-800 rpm), using a good quality multimeter:
1. Check voltage at B+ large HOT alternator output post.
2. Check voltage at alternator (input) post on battery isolator.
3. Check voltage at chassis battery post on isolator.
4. Check voltage at coach battery post on isolator.
5. Check voltage at POS post on chassis battery bank.
6. Check voltage at POS battery post on coach battery bank.
While doing these voltage checks, look for loose, corroded cable connections or frayed cables.
Let us know the results.
A 2001 has the dreaded blue box that sometimes gives bad info. Look for threads on it.
When the tech checked the voltage at the alternator 14.5 at the batteries 12.5 v. Would older weak house batteries contribute to low voltage?
House voltage is independent of chassis voltage unless the boost switch is on.
Rather than guessing, can the "tech" (or someone) give us the readings I asked for in Reply #1?
The goal is to find the "weak link" in the charging circuit. This requires a systematic approach to trouble shooting.
Will do. I don't have access to the voltmeter at the moment. Will perform volt test and will report back. Thank you.
As you have voltage at the alternator, the first thing I would check the voltage at the isolator and then follow
follow Chucks chart..\
Article in current motorcader magazine. Suggests it could be isolator.
Thanks everyone. At the coast and do not have the ability's to check at the moment. However, question, I have 13.5 v when running the generator? Is it ok to run the generator to keep the voltage up until I get home?
Don't think that should be a problem. Where/How are you reading 13.5 volts? On the backup monitor? Do you have a 12v socket that shows voltage? On my 2000 the two 12v plug in sockets on the dash, the top socket shows voltage on the house batteries and the bottom shows voltage on chassis batteries. I would probably run the generator and turn the boost switch on so the generator will be charging both sets of batteries.
Headlights on or off? I've seen the dash reading drop by over 0.5V when the lights come on especially if you have a trailer or toad with lights as well.
Many owners have ran their generator for many days when their isolator has failed when going down the road.
Yes, the generator will "power" the inverter/charger or converter to charge the HOUSE battery bank.
On some, it will also charge the CHASSIS battery bank-- but that is more the exception than the rule.
If the BOOST SWITCH/RELAY is activated (and working), it will also charge the chassis battery bank, which is critical for driving.
If boost switch/relay is not working (easy to tell, as both banks will have the same voltage if it is working), easy to work around-- usually as easy as moving one wire and adding it to another.
One way to test the isolator if you don't have a voltmeter is to take the leads of the isolator and
hook them altogether and see if you voltage goes up. If the voltage goes up, drive that way and
at night disconnect them.