Interlocks and lockouts

On motorhomes, and on some towables, the room won't move until other inputs say it's safe: park brake, ignition, transmission, jacks, bay doors. A dead slide on a coach is often a lockout input that isn't arriving, so prove the input before you chase the motor.

The short version

• Requirements vary and contradict: Lippert's in-wall manual says ignition off on motorized units, while Lippert's Above Floor and Tiffin's Spyder coaches want the ignition on or the engine running.
• A park brake input is a switched signal. SlimRack's park brake fault check is ground continuity at the park brake connector.
• HWH room extensions won't run the pump with the park brake off or a bay door under the room open, and HWH runs rooms at ride height with the jacks retracted.
• Prove a lockout at the controller: the input should change when you set and release the condition.
• If other rooms or the levelers work, the shared inputs are probably good. Use that before you start tracing wires.

What the makers require

Each maker publishes its own list and they don't agree. A tech who knows one coach and assumes the next one is the same is the first trap.

How they're wired

A lockout is an input to the slide controller, a relay in the slide feed, or a switch in series with the room control. The SlimRack manual shows the first kind: for a park brake fault it has you check ground continuity at the park brake connector, which tells you the input is a ground signal from the park brake switch. An open anywhere in that wire reads as brake off.

HWH shows the series kind: its schematic puts bay door switches in the room control circuit, so an open bay door, a bad door switch or a broken wire to one stops the pump.

Ignition, transmission and jack inputs come from the chassis or leveling side of the coach, so their wiring runs through OEM connectors and splices that the slide maker never drew. That's where they fail.

How they fool you

The classic motorhome call is slides dead, levelers fine. On one owner-reported 2011 Itasca, both slide panels flashed 'engage park brake' with the brake set while the HWH leveling panel saw the brake correctly, and a new park brake switch didn't fix it. That pattern points at the slide's branch of the park brake signal, not the switch.

Other ways a lockout hides: the key is in the wrong position for this coach, the chassis battery is low on a coach whose slides run from it, the system wants the engine running and the owner is on the generator, or the jacks aren't where the system wants them. On HWH, a bay door left open under the room is a dead room with no code.

Don't call a slow start a lockout too soon. Lippert's SlimRack manual says a slight delay before the room starts moving is normal.

And don't skip the basics because it's a motorhome. A tripped breaker at the battery also gives you a dead room with no sound, so check the feed before you trace an interlock.

Proving a lockout

Treat a lockout like any other input. Find it on the wiring diagram, find where it lands at the controller or relay, and watch it change.

1. Set every condition the manual lists (brake, key, transmission, jacks, bay doors, seats) and confirm each one physically.
2. Read the slide controller or panel. Many show a park brake or interlock message or LED.
3. At the controller connector, check the input with the condition met and not met. A park brake ground input should read ground with the brake set and open with it released.
4. If the input never changes, trace back toward the switch through connectors, splices and fuses.
5. If the input is right and the room still won't run, the lockout isn't your problem. Go back to power and the controller.

Careful: Don't leave an interlock jumpered so the customer can run the room. Park brake and transmission inputs keep a room from moving while the coach can roll; jumper one only as a brief test with the coach secured, then remove it.

Other rooms and shared circuits

When one pump or controller serves several rooms, a shared input kills them all. HWH's pump list applies to every room on that pump, so one open bay door switch or a missing park brake signal makes every room look dead.

Rooms can also lock each other out physically. Tiffin requires the driver's and passenger's seats moved forward and locked before the front slides run. If one room is dead and the others work, the shared lockouts are proven and you're back to that room's own feed, switch and controller.

On the job

1. Get this coach's slide requirements from the OEM manual: key position, engine, park brake, transmission, jacks.
2. Set them all and confirm physically: brake set, in park, jacks where the manual wants them, bay doors shut, seats forward.
3. Check whether other rooms and the leveling system work, to sort shared inputs from this room's own circuit.
4. Check the slide feed and breaker at the battery so a dead circuit isn't mistaken for a lockout.
5. Read the slide controller or panel for an interlock message or LED.
6. Test the interlock input at the controller with the condition met and not met, and trace a dead input back to its switch.

Numbers

• HWH room switch hold: 3 to 4 s after full travel to pressurize the cylinders; never more than 10 s
• Lippert in-wall electronic override: Controller returns to normal mode if the wall switch isn't pressed within 60 s

Shop tip

When the slides are dead and the jacks work, ask the leveling panel. If it sees the park brake and the slide panel doesn't, you've narrowed it to the slide's branch of that wire in one look.

Where this comes from

• Lippert, In-Wall Slide-Out Owner's Manual, CCD-0001602, pp. 3, 4; In-Wall Troubleshooting Guide CCD-0001771, pp. 6, 8
• Lippert, Above Floor Slide-Out Owner's Manual, CCD-0001598, rev 07.12.18, p. 3
• Lippert, SlimRack Slide-Out Owner's Manual, CCD-0001459, rev 07.30.18, pp. 7, 10, 11
• HWH room extension operator's manual ML17127 (16MAR01), room extend, retract and troubleshooting sections (Tiffin owner hub)
• Tiffin 2018 Allegro Breeze and 2019 Allegro Open Road owner's manuals, section 10 slide-out features
• Lippert, Level-Up Owner's Manual, rev 12.27.2017, pp. 11, 13

Try it on a service call

Put the lesson to work on a hands-on troubleshooting case.

• Slide dead both ways, no sound