1992 Chevy Mallard Sprinter Electrical Problems

[joshtb86]

Hello!

I purchased a 1992 Chevvy Mallard Sprinter used with 31k miles on it and noticed the following issue:

When I turn on the chassis battery, none of the chassis 12v utilities run (fridge, lights, fans).

If I run the motor and the alternator is on, the 12v chassis utilities operate.

None of the AC utilities operate unless it is plugged into a shore line or the AC generator is running.

I am brand new to RVs and do not really have an idea of where to start. Any help is appreciated.

Thanks!


This is the carfax info

1990 CHEVROLET P30
MOTORIZED HOME
7.4L V8 TBI OHV
GASOLINE
REAR WHEEL DRIVE

[MrWizard]

no...

do your interior RV lights and water pump work, when the engine is running ?

if yes, then the path from rv batteries to house is good, and converter is bad

IF NO, then you still have the break in the circuit as i described it

you have proven the alternator charge circuit is good

you have NOT proven the batteries are good and hold the charge, or that there is circuit between batteries and converter/house fuses and wiring

like i said IF things work when shore power is on

look for the break in the circuit

[joshtb86]

MrWizard wrote:
If you have 12v power when plugged in, lights etc.. work
Then the converter is putting out power, might be low voltage, but it is power

It sounds like there is a break in the circuit between the batteries and the converter/house wiring
This could be a blown fuse, but is more likely a loose disconnected or missing wire

Start at the house batteries
Follow the wire, it should run to the battery disconnect relay
Check voltage on both side ( the big stud terminals )

If the battery side is 11.8v
And the other side is 13-14v you have found the problem
Temporary fix is remove the nuts on the studs and move the battery wire to the charge side, where the good voltage is at, and then put a nut on there and tighten it down

You can do it the other way it needed
Which ever wire is easier to move
Just so you get both wires together

Give it 24 hours of charging, before you unplug shore power, or generator, to give the batteries a chance to recover

thanks!

i havent gotten to this yet but found this

the batteries do NOT charge when i have AC power on either via shoreline or generator, only when the engine is on with the alternator running

then the batteries all have voltages of 13+

does this mean the charge converter is not working? or could this be how it was designed?

[MrWizard]

If you have 12v power when plugged in, lights etc.. work
Then the converter is putting out power, might be low voltage, but it is power

It sounds like there is a break in the circuit between the batteries and the converter/house wiring
This could be a blown fuse, but is more likely a loose disconnected or missing wire

Start at the house batteries
Follow the wire, it should run to the battery disconnect relay
Check voltage on both side ( the big stud terminals )

If the battery side is 11.8v
And the other side is 13-14v you have found the problem
Temporary fix is remove the nuts on the studs and move the battery wire to the charge side, where the good voltage is at, and then put a nut on there and tighten it down

You can do it the other way it needed
Which ever wire is easier to move
Just so you get both wires together

Give it 24 hours of charging, before you unplug shore power, or generator, to give the batteries a chance to recover

[garry1p]

If you had it plugged in for 15 hours and the batteries are at 11.8 they are bad and won't take a charge OR your converter is bad and not putting out a charge voltage.

To test converter with the RV plugged into shore power measure the voltage at the coach (house) batteries they should be 13+ volts and charging the batteries.
Unplug from 120V and measure they should be around 12.6 or above.

You might be able to save the batteries by charging with a regular auto battery charger.

Also check to make sure the converter circuit breaker has not tripped.

[MrWizard]

It is normal for the fridge to be lp gas or 110ac

12v operation is not normal

They used to make fridge with 12vdc operation, but it was a travel mode for maintaining cold with out using the lp
It was never very efficient , and was phased out a long time ago

Your Mallard does not have a DC option, but it must have 12 volts for the control board, or it won't come work on LP or 110v

11.82 is not totally dead but it is between 30-40% charge status, and needs a good full recharge
Modern batteries are 12.8v or above when fully charged

[DougE]

It's been a long time since I let my '91 Mallard go, but is seems to me a toggle switch on the dash in front of the driver operated a solenoid on the firewall behind the driver's headlight.

[darsben1]

Sometimes they are above the door and are momentary rocker switches. If you push the switch you will hear a clunk in another part of the coach which will be the relay turning on. I do not have a Mallard so I cannot tell for certain but usually somewhere near the door

[joshtb86]

MrWizard wrote:
ok
#1 all RV house lights, water pump, fans, heater blower, and fridge control circuits, etc.. are 12v and work from the coach/house batteries

#2 you should have (2) or more batteries, (3) is common, (1) for engine/chassis, (2) for RV side

#3 the battery switch, disconnects the RV/house batteries for storage
batteries should NOT be disconnected unless you are 'storing' RV and not using it, 'all camping' needs the batteries connected 'ALL the time', until you get home, empty the fridge and put the RV to bed

#4 good news is you generator and charge converter are working

#5 bad news your house side batteries are dead/disconnected /or missing

#6 the only thing you should do with an inverter is, watch TV, and charge things like phones and tablets etc..

major heavy power use aka microwave , coffee pot, A/C, hair dryer, etc
has to be from generator or shore power, unless you invest $$ in a big battery bank and a large inverter, and even then you will need to run the generator during the day to recharge the power you used from the batteries the night before

a 300-400w inverter, is large enough to handle all your entertainment/ internet needs

most people, just run a separate circuit from inverter to where the entertainment recharge power is needed, that makes it available all the time, with NO switch over issues, cords etc.. needing to be moved

thanks! they are dead - 11.82v checked this AM

fridge works on AC or gas but not at all on DC currently

[joshtb86]

MountainAir05 wrote:
You should check all the batteries at the battery termale . As stated the battery switch should be on. You should have 12.6v or there abouts. NOT 12 volts on each battery installed. If you have 12.6v at all batteries and no power is applied then the batteries are good. If not then plug in to shore power and check voltage on all batteries. Should be 13.x . That will tell you the batteries that have that voltage are being charged. Not all batteries get charge on every RV. Some do and some don't. I am assuming that you only have 2/3 batteries at max, so you would not have a inverter installed. If only one battery nothing would run but a few minutes. If two batteries for the RV side then maybe a TV or something else for a short time.

When you have all AC power off does your refrigerator work? If not when you plug in AC does the refrigerator work then.

fridge doesnt work with AC power off.

RV batteries are dead checked this AM and they were at 11.82v.

is it possible to recharge them from that point or do they need to be replaced? ive had it plugged in/generator running for probably about 15 hours total now.

[joshtb86]

darsben1 wrote:
Are the battery disconnect switches on?

im not even sure where to find the disconnect switch on this model. any ideas of where to start?

[MrWizard]

ok
#1 all RV house lights, water pump, fans, heater blower, and fridge control circuits, etc.. are 12v and work from the coach/house batteries

#2 you should have (2) or more batteries, (3) is common, (1) for engine/chassis, (2) for RV side

#3 the battery switch, disconnects the RV/house batteries for storage
batteries should NOT be disconnected unless you are 'storing' RV and not using it, 'all camping' needs the batteries connected 'ALL the time', until you get home, empty the fridge and put the RV to bed

#4 good news is you generator and charge converter are working

#5 bad news your house side batteries are dead/disconnected /or missing

#6 the only thing you should do with an inverter is, watch TV, and charge things like phones and tablets etc..

major heavy power use aka microwave , coffee pot, A/C, hair dryer, etc
has to be from generator or shore power, unless you invest $$ in a big battery bank and a large inverter, and even then you will need to run the generator during the day to recharge the power you used from the batteries the night before

a 300-400w inverter, is large enough to handle all your entertainment/ internet needs

most people, just run a separate circuit from inverter to where the entertainment recharge power is needed, that makes it available all the time, with NO switch over issues, cords etc.. needing to be moved

[MountainAir05]

You should check all the batteries at the battery termale . As stated the battery switch should be on. You should have 12.6v or there abouts. NOT 12 volts on each battery installed. If you have 12.6v at all batteries and no power is applied then the batteries are good. If not then plug in to shore power and check voltage on all batteries. Should be 13.x . That will tell you the batteries that have that voltage are being charged. Not all batteries get charge on every RV. Some do and some don't. I am assuming that you only have 2/3 batteries at max, so you would not have a inverter installed. If only one battery nothing would run but a few minutes. If two batteries for the RV side then maybe a TV or something else for a short time.

When you have all AC power off does your refrigerator work? If not when you plug in AC does the refrigerator work then.

[darsben1]

Are the battery disconnect switches on?

[joshtb86]

Krusty wrote:
Sounds like it is operating normally. None of the things you mentioned (fridge, lights, fans) would run off the chassis battery. They would run off the coach battery. None of the 120 volt AC stuff will run off the 12 volt system unless you have them connected to an inverter.

okay so follow up ?s

1. if i connect the 12v dc batteries to an inverter, and connect that to the AC system, i would be able to run the AC stuff off the dc batteries?

2. sorry if this wasnt clear - i cannot run any of the dc stuff (lights in the back, etc) off either battery - they simply do not work unless the alternator is running. does that mean the batteries are dead?