Dash gauges voltage issues Dynasty Roadmaster

[jeepmedic]

Hey guys, thanks in advance for any help. This is a little long winded so be gentle.
1998 Dynasty 8.3 mechanical, Roadmaster chassis. I have an issue with my dash gauges that started a couple years ago. All seem to read correctly for the most part except for the charge gauge. It will read as high as 12.5 (ish) after being on shore power. After driving some time it will fall to 12 then to 11. Never really seen it lower. I tested the output of the alternator at the battery and I have 13.4 -14 V. So knowing this didn't make sense I drop tested the ground termination block behind the generator door. I have virtually no drop (less than .2 loaded) At the ignition solenoid in the front run box I have B+ and ground tests good but when I key the ignition on, engine off I'm showing around 12.4v. The solenoid closes and powers the sub fuse panels and the fuses have 12.4 same as the B+ termial on the relay. I removed the instrument panel and went to back of the ignition switch, various gauges and the charge gauge, all have between 10.8-11v. I know grounds are crucial but mine are good. So far the only issue has been guage inaccuracy but I know it WILL become an issue with the voltage being low. Is there another module that feed the switched voltage to the guages? What am I missing here? Trying to not diassemble too much here unless I have to.

[153stars]

I think the dash area if fed by a 10ga wire off the positive chassis battery with an inline fuse on it within a foot. Check bad connections , tired corroded crimp connector and inline fuse connections.
I also think there is a ground bus bar under the dash.

[veraken]

Here's a WAG. I had a similar problem on shore power where my batteries were only being charged at @ 12.5v or less. After investigation I found that it was due to a bad temp sensor from my inverter ( I have a Trace RV2012) to the battery. Disconnect your temp sensor and see if things change. I confirmed this by talking to Xantrex and they do not have a replacement and they said just leave it disconnected - not needed.

[jeepmedic]

Originally Posted by veraken

Here's a WAG. I had a similar problem on shore power where my batteries were only being charged at @ 12.5v or less. After investigation I found that it was due to a bad temp sensor from my inverter ( I have a Trace RV2012) to the battery. Disconnect your temp sensor and see if things change. I confirmed this by talking to Xantrex and they do not have a replacement and they said just leave it disconnected - not needed.

This is interesting. My temp sensor is wedged between the case and battery. No longer sticky to the battery. I will try unplugging it. Still doesn't explain why driving the voltage guage doesn't show charge voltage. Thanks

[CountryB]

Originally Posted by jeepmedic

I have an issue with my dash gauges that started a couple years ago. All seem to read correctly for the most part except for the charge gauge. It will read as high as 12.5 (ish) after being on shore power.

That might be normal as on some Coaches (probably yours) the Chassis batteries will not charge on Shore Power. So you are reading the discharged Chassis battery while the Inverter/Charger charges up the House batteries.
Newer Coaches have the ability to charge both Chassis and House batteries on Shore Power (such as with the Big Boy solenoid and BIRD relay).

After driving some time it will fall to 12 then to 11. Never really seen it lower. I tested the output of the alternator at the battery and I have 13.4 -14 V.

This is a problem. Your dash voltmeter should read the chassis battery voltage (13.4 - 14V) when the engine is running.
Perhaps the dash gauge is broken and wont read into the 12.5+ range. You could try to run a temp wire from the ignition switch (or wherever) you have a confirmed 13.4+ volts to the Voltmeter to see if it will display correctly.

At the ignition solenoid in the front run box I have B+ and ground tests good but when I key the ignition on, engine off I'm showing around 12.4v. The solenoid closes and powers the sub fuse panels and the fuses have 12.4 same as the B+ terminal on the relay.

If your chassis batteries are "actually" reading 12.4 (engine not running), which would mean the batteries are not fully charged up, then this would be expected.

I removed the instrument panel and went to back of the ignition switch, various gauges and the charge gauge, all have between 10.8-11v. I know grounds are crucial but mine are good.

You have some voltage drop between the power source and the ignition switch. You should at least be getting the 12.4V you are seeing in the Run box. You can try to isolate by disconnecting the ignition switch plug and then seeing if you have 12.4V. If you do the voltage drop is after the switch. if the voltage still reads low, check the wire from the Run bay to the ignition switch.

The wiring diagram show the Voltmeter gets its source form the oil pressure gauge - which gets its power form the 15A fuse in the ignition fuse block. Find this fuse and check the voltage on it (pull the fuse (to eliminate any drop on the supply side of the circuit) and check the supply voltage going to the fuse. Is it 12.4?)

[jeepmedic]

Originally Posted by CountryB

That might be normal as on some Coaches (probably yours) the Chassis batteries will not charge on Shore Power. So you are reading the discharged Chassis battery while the Inverter/Charger charges up the House batteries.
Newer Coaches have the ability to charge both Chassis and House batteries on Shore Power (such as with the Big Boy solenoid and BIRD relay).



This is a problem. Your dash voltmeter should read the chassis battery voltage (13.4 - 14V) when the engine is running.
Perhaps the dash gauge is broken and wont read into the 12.5+ range. You could try to run a temp wire from the ignition switch (or wherever) you have a confirmed 13.4+ volts to the Voltmeter to see if it will display correctly.



If your chassis batteries are "actually" reading 12.4 (engine not running), which would mean the batteries are not fully charged up, then this would be expected.




You have some voltage drop between the power source and the ignition switch. You should at least be getting the 12.4V you are seeing in the Run box. You can try to isolate by disconnecting the ignition switch plug and then seeing if you have 12.4V. If you do the voltage drop is after the switch. if the voltage still reads low, check the wire from the Run bay to the ignition switch.

The wiring diagram show the Voltmeter gets its source form the oil pressure gauge - which gets its power form the 15A fuse in the ignition fuse block. Find this fuse and check the voltage on it (pull the fuse (to eliminate any drop on the supply side of the circuit) and check the supply voltage going to the fuse. Is it 12.4?)

Excellent! I have the diagrams for the coach except for the dash / ignition switch. Would you happen to have that?

[CountryB]

I have collected a few Dynasty diagrams for your era Coach. You can download them from my OneDrive site.

The link is in my signature line.
Open the link and go to the "1984-1999 Wiring Diagrams" folder, then to the "1992-1999 Monaco" subfolder.

Good luck