Something shorted

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.

mlrailguy

Member
Joined
Jun 7, 2021
Posts
10
Location
98837
My coach batteries were not charging from alternator. I tried using jumper cable to jump them. I heard engine slow down for moment and now the alternator is not charging at all. Do I replace alt. or is there a fuse someplace? The MH is a 93 Winnebago Vectra.
 

donn

Well-known member
Joined
Nov 8, 2009
Posts
4,358
How do you know the alternator is not working? Have you used a volt meter to check the alternators output voltage? You could take the alternator to someplqce like autozone and,they can check it for you.
 

mlrailguy

Member
Joined
Jun 7, 2021
Posts
10
Location
98837
How do you know the alternator is not working? Have you used a volt meter to check the alternators output voltage? You could take the alternator to someplqce like autozone and,they can check it for you.
I have checked at battery, only have 12.03 volts. As soon as I get battery charged up and engine started, I will check at alt. The gauge on dash reads 9 volts
 

JayArr

Well-known member
Joined
Jun 13, 2020
Posts
236
Location
Mission British Columbia Canada
Sounds like you blew the alternator trying to charge the house batteries. Did you disconnect the house batteries from the house before you put the jumper cables on them? That would make troubleshooting easier since it would mean the short is in the batteries. If they were still hooked up to the house and you put jumper cables on them there is still the possibility there is a short somewhere in the house or the converter.
 

mlrailguy

Member
Joined
Jun 7, 2021
Posts
10
Location
98837
Sounds like you blew the alternator trying to charge the house batteries. Did you disconnect the house batteries from the house before you put the jumper cables on them? That would make troubleshooting easier since it would mean the short is in the batteries. If they were still hooked up to the house and you put jumper cables on them there is still the possibility there is a short somewhere in the house or the converter.
Yes, house batteries were still connected
 

JayArr

Well-known member
Joined
Jun 13, 2020
Posts
236
Location
Mission British Columbia Canada
Do the batteries charge OK when you're plugged into shore power? Or do they not charge at all.

Could be a short in one of the batteries, could be a short in the power converter that charges them or could be a short in the house wiring or house appliances.

The first thing I would do is get my alternator working, as a bonus, places that repair alternators also test batteries so pull your house batteries and have them load tested.

If the batteries are OK then check to see if power is getting from the alternator to the house batteries. With the house batteries disconnected measure the voltage on the cables that go to them with the engine running. What is the voltage?
 

Kirk

Well-known member
Joined
Oct 30, 2005
Posts
286
Location
Full-time , Escapee
Did you use jumper cables between the chassis battery and the house battery? Are you sure that the jumper was properly connected?
 

SLOweather

Well-known member
Joined
Dec 2, 2018
Posts
334
Stupid question time:

Is there a possibility you hooked the cables up backward? (Been there)
 

mlrailguy

Member
Joined
Jun 7, 2021
Posts
10
Location
98837
Do the batteries charge OK when you're plugged into shore power? Or do they not charge at all.

Could be a short in one of the batteries, could be a short in the power converter that charges them or could be a short in the house wiring or house appliances.

The first thing I would do is get my alternator working, as a bonus, places that repair alternators also test batteries so pull your house batteries and have them load tested.

If the batteries are OK then check to see if power is getting from the alternator to the house batteries. With the house batteries disconnected measure the voltage on the cables that go to them with the engine running. What is the voltage?
Yes, house batteries charge fine with shore power. Just checked alt, only getting 12.08 volts from it.
 

Kirk

Well-known member
Joined
Oct 30, 2005
Posts
286
Location
Full-time , Escapee
Just checked alt, only getting 12.08 volts from it.
If that is from the chassis, the voltage you would read should rise as the battery charges. Basically the alternator pushes current into the positive side of the battery to fill it and as it charged that battery voltage rises and it should reach 14.4V as the battery is fully charged. The voltage regulator then drops the output from the alternator down to something around 13.6 - 13.8V and maintain that. When things are working as they should, there is a solenoid that connects the output of the alternator to the coach battery(ies) to charge them also. If your coach still has the original converter, it should supply about 13V to 13.5V but no more. As with the chassis battery, the voltage would depend on how nearly charged the batteries.

A typical wet cell, 12V battery is actually at about 13.6V when fully charged and slowly drops to 10.5V under normal conditions, but if kept in service without charging it could fall much lower and a damaged battery can read far lower.

You should be able to find a battery cable that goes from the coach battery to the cross-connect solenoid that is probably located somewhere near the chassis battery, usually on the firewall for the engine. It would also have another battery cable from it to some common connection with the chassis battery and a small wire that is the control power to close the contacts when appropriate.

I hope that this is some help.
 

mlrailguy

Member
Joined
Jun 7, 2021
Posts
10
Location
98837
OK, got new alt in. Only putting out 12.05 volts. The converter is charging house batteries fine at 13.68.
Stupid question time:

Is there a possibility you hooked the cables up backward? (Been there)
maybe, but i have been jumping cars for 50 years
If that is from the chassis, the voltage you would read should rise as the battery charges. Basically the alternator pushes current into the positive side of the battery to fill it and as it charged that battery voltage rises and it should reach 14.4V as the battery is fully charged. The voltage regulator then drops the output from the alternator down to something around 13.6 - 13.8V and maintain that. When things are working as they should, there is a solenoid that connects the output of the alternator to the coach battery(ies) to charge them also. If your coach still has the original converter, it should supply about 13V to 13.5V but no more. As with the chassis battery, the voltage would depend on how nearly charged the batteries.

A typical wet cell, 12V battery is actually at about 13.6V when fully charged and slowly drops to 10.5V under normal conditions, but if kept in service without charging it could fall much lower and a damaged battery can read far lower.

You should be able to find a battery cable that goes from the coach battery to the cross-connect solenoid that is probably located somewhere near the chassis battery, usually on the firewall for the engine. It would also have another battery cable from it to some common connection with the chassis battery and a small wire that is the control power to close the contacts when appropriate.

I hope that this is some help.
Could I have shorted one of the solenoids? There is one with 3 posts and another one below it with 4 posts. I wasn't getting any power to house batteries from alt is why I tried to jump them (trying to start generator)
 

Kirk

Well-known member
Joined
Oct 30, 2005
Posts
286
Location
Full-time , Escapee
If you shorted across the one for connecting while the engine is running it would do the same as connecting jumper cables. The coach batteries and the chassis battery all use a chassis ground so that is common and all that solenoid connects is the positive side. There is probably also an emergency start switch on the dash that connects the two batteries and in some RVs it uses the same solenoid while others have 2 separate ones so that may be what you have located Trace the lager battery cables to see where they go.
 

mlrailguy

Member
Joined
Jun 7, 2021
Posts
10
Location
98837
I have drawn a diagram of wiring as best as I can see.
 

Attachments

  • 20210611_073929.jpg
    20210611_073929.jpg
    77.7 KB · Views: 9

Gary RV_Wizard

Site Team
Joined
Feb 2, 2005
Posts
73,527
Location
At our Silver Springs FL home
Are the boxes in that diagram batteries or relays? Does "to house" mean toe the actual house battery, or to some other component on the house side? There should be an isolation relay between house side and chassis side electrical, and that relay will be open or closed depending on conditions (and a manual override swich as well).
 

mlrailguy

Member
Joined
Jun 7, 2021
Posts
10
Location
98837
Are the boxes in that diagram batteries or relays? Does "to house" mean toe the actual house battery, or to some other component on the house side? There should be an isolation relay between house side and chassis side electrical, and that relay will be open or closed depending on conditions (and a manual override swich as well).
They are the solenoids
 

mlrailguy

Member
Joined
Jun 7, 2021
Posts
10
Location
98837
New alternator, tested good at 2 separate places. Still only 12 volts at alt when running.
Here is rundown of tests I've done.
All batteries charged
Shoreline unplugged and house batteries disconnected; House batteries @ 13.15 volts
Chassis battery @ 12.19 volts
0 voltage at both solenoids
Engine running 11.85 volts @ chassis battery
Dual Battery switch @ neutral 0 volts @ both solenoids
dual 11.23 volts at small post on top solenoid (3 post)

Shoreline unplugged, House batteries connected 13.11 volts
Chassis battery 12 volts

Engine running, switch in neutral 13.11 volts @ House batteries
11.78 volts @ Chassis battery
dual 12.84 house
11.76 chassis

Top solenoid....dual position 12.83 on left post
11.12 center post
12.83 right post
neutral 12.82 on left post
0 at center post
12.82 on right post
Bottom solenoid ( both positions ) 12.82 at left post
0 at both center posts
0 on right post
 

Forum statistics

Threads
118,529
Posts
1,187,727
Members
123,114
Latest member
Georgepro
Top Bottom