1999 Diplomat No Power to Ignition SW or Panel

[Bob72]

Hi, new to this forum. I just purchased a 1999 Diplomat. Changed all the batteries. Tried a test start at the house (with slide extended). After a couple seconds of starting the ignition stopped and instrument panel went blank. No air warning, no nothing. Radio inop too. Checked the car type fuses under the driver locker. All good. Removed inverter to get to the relays in the back right side locker. No diagram of what’s what.

This MH has a 275 Cummins. Generator works fine, slide works fine, interior lights fine. Coach power seems normal. No power to step.

Can’t find this issue anywhere, including YouTube. Any help appreciated.

Thanks, Bob

bob.stienke@gmail.com

[MSHappyCampers]

Hi Bob! Welcome to IRV2! We're sure glad you joined the gang!

Congrats on the new rig! Sorry you're having trouble right out of the chute!

Did all this happen immediately after replacing the batteries? Many folks that replace multiple batteries get the new ones wired wrong if they didn't take a photo or make a drawing before doing the replacement. Just a thought.

Good luck, happy trails, and God bless!

[mlh2013]

I would first double check the connections on the chassis batteries make sure they are clean and tight.

[8.3Oilbuner]

Good afternoon Bob; Sounds like you might have lost the chassis power side to the coach. I know you charged the batteries so they should be up. After this happened have you rechecked the chassis batteries to see if they are still fully charged. If you only tried a short time of cranking the engine those chassis batteries should still show at least 12.6V. I would start there and see what info you get. Also, are all the other chassis powered items working like headlights and marker lights? One other thing to check, because this has happened to others, is the chassis power disconnect switch. I think yours is in the battery bay. One for the house and the other for the chassis. Under a load sometimes they fail or the connections on the back of the switch come loose. See if you have 12V on the out going side of the switch to the chassis. Also down from the switch are some circuit breakers but I think they reset automatically after something happens. All I can think of at the moment. Let us know when you have a fix so others here can benefit from your experience. Good luck!

[kidz_driver]

Hi Bob,

Changing batteries seems to trip up a lot of people. As noted earlier taking pictures is a good idea.

On the Diplomat there are a couple of areas to look at. The w relays behind the inverter supply power to the VP44 injection pump and the intake grid heater. (the Cummins ISB uses an intake grid heater rather than glow plugs for cold weather starts).

I'm assuming that your description is that the engine turned over for a few seconds before everything went blank on the chassis side. This is often indicative of a poor ground. Recheck your negative battery cable connections. Make sure that all the smaller gauge wires have been reconnected to the batteries (2 reds to positive terminals and the 5 whites to the negative terminals).

There are 7 fuses on the back wall of the battery compartment which supply power to the Cummins ECM and the Allison Transmission Control Module. If the TCM does not have power, the shifter pad will not illuminate. There is an interlock between the transmission and the ECU. If the ECU does not receive a signal from the transmission you will not get power to the ignition switch.

If you have access to a multi-meter, check for voltage on both sides of the Guest switch in the battery compartment. This is sometimes a problem area.

Good luck

Dave

[Bob72]

Thanks Dave!

[Bob72]

Guys,

Thanks so much for your replies. I just got back from the battery compartment. No voltage beyond the Guest brand On/Off switch. Had 12.65 volts out of the chassis battery, 13.35 out of the coach batteries.

Took the chassis Guest switch off, the Batt 1 terminal was leaning at a 45 degree angle, with puddling of plastic at its base. Failure for sure.

I will replace this tomorrow, then look for why the heavy load. Suspecting starter hot lead loose or corroded or chassis ground loose/corroded. At least I have a direction. I thought it was a fried relay or 12.

Thank all of you for your suggestions!

Bob

[8.3Oilbuner]

Hi Bob; Well that's good news! When a terminal melts like that it is a sign of a loose connection. The, not tight connection creates a high resistance. That causes heat. When the starter is running there is a big amp draw and if that is going through a bad or loose connection, well, you can see what happens. I think you have found your problem. Let us know if replacing the battery disconnect switch solves your problem. Have a great evening!

[twinboat]

Originally Posted by Bob72

Guys,

Thanks so much for your replies. I just got back from the battery compartment. No voltage beyond the Guest brand On/Off switch. Had 12.65 volts out of the chassis battery, 13.35 out of the coach batteries.

Took the chassis Guest switch off, the Batt 1 terminal was leaning at a 45 degree angle, with puddling of plastic at its base. Failure for sure.

I will replace this tomorrow, then look for why the heavy load. Suspecting starter hot lead loose or corroded or chassis ground loose/corroded. At least I have a direction. I thought it was a fried relay or 12.

Thank all of you for your suggestions!

Bob[emoji144]

You found your loose connection, it was the Guest switch terminal.

Make sure the replacement switch is rated to carry the starter current draw. That can be up to 600 amps. Some are not rated that high.

Loose or corroded connections cause resistance and that causes heat. They do not cause excessive amp draw.

Good connections to bad starter motors or hard to crank engines can.

[Bob72]

Hi guys,

I changed out the chassis battery switch, cleaned the starter hot battery lead, and searched above and below for the chassis ground wire location. No luck!

The engine turns over very slowly now. Power restored to the ignition, instrument panel and step.

Does anyone know the location of the chassis ground attach point for a ‘99 Diplomat? Service guys here in upper Indiana for RVs don’t know?

Thanks guys!

Bob

[twinboat]

Crank the engine for 10 seconds and then feel the switch, cable connections and starter if possable.

Any unusual hot connections areas are suspect.

You can also borrow a starter draw meter from a auto parts store and see what the amp draw is. Its a simple gauge that you hold against the starter cable.

[kidz_driver]

Bob,

Did you try holding the red "aux start" button on the dash when cranking the engine over. It connects the house batteries into the starting circuit and increases the available cranking amps. It does this through the large relay in the center of the back wall of the battery compartment. Also provides a secondary ground since the house batteries have their own ground connection.

Dave

[153stars]

When I bought my rig the chassis batteries were tired and wouldn't stay juiced off the charger for more than few days even with disconnect off .There were two 3yr old cranking 4D. batteries for house batts.The genny didn't want to crank over either.I cleaned a pair of grounds daisy chain on top of frame between battery box and motor and the starter had another ground lower on frame and starter had its own ground as well. I think there was a bare flat braided between trans. and frame as well. I'm sure some were for house batteries. I just cleaned every thing I laid my hands on.I don't think my boost solenoid relay was very good.
Ended up moving the pair of 4D to chassis and buying 4 new Sam's club GC2 batteries. The M11 cranks like the dickens .

[Bob72]

Thanks 153 stars! As soon as the temp is up a little I’ll get back at it. 15 here with 4” of snow.