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Sync, timing and when the column is done

Out of sync means the two sides are uneven, and the controller can fix it. Out of time means the top and bottom of one side are uneven, and only re-meshing that column's racks fixes it.

The short version

Sync versus time

Sync is side to side. The controller counts each motor's pulses and references them to the ends of travel. When the room doesn't reach full in or full out, from low voltage, an interrupted move or a bind, the count drifts and one end leads. The motors stop at different times and the room sits crooked in the opening.

Time is top to bottom on one side. The torque shaft turns the upper and lower spur gears together, so the racks stay in step unless one jumps a tooth. Lippert's assembly manual puts it simply: when the system is out of time, either the top or the bottom extends farther than the other. The controller can't see that, because it's all one motor.

Resynchronizing the motors

This is the current Lippert procedure from the owner's and service manuals. Get the voltage right first, or the resync just fails again.

  1. Fully extend the room with the switch and keep holding until the motors shut off on their own.
  2. Retract the room 1 to 2 in.
  3. Repeat until both motors shut off at the same time. Two or three cycles is normal.
  4. Fully extend, then fully retract, holding the switch each time until the motors stop.
  5. Both motors stopping together at both ends means it's in sync. If not, repeat.

Measure before you decide

When a resync doesn't settle it, measure. Lippert's tolerance check (the QR-085 forms) measures from the outside edge of the column to the face of the gear rack at all four corners, once fully extended and once with the room 3 in from fully retracted. Non-standard installs use the RV maker's numbers.

Separately, measure how far the room sticks out at the top and bottom of each end. That's your sync-or-time answer.

What you seeWhat it means
One end ahead, top and bottom even on each endOut of sync. Voltage, then resync.
Top and bottom differ on one end, other end evenThat column is out of time. Re-mesh its racks.
Column edge to rack face outside 2-3/8 to 2-5/8 in at any cornerOut of Lippert's tolerance. Find out why before replacing parts.
Racks more than 1/8 in out of parallelOut of tolerance. Racks must be parallel.
Seal binding, or not about 1/4 in of overlapSeal fit problem (lesson 7).

Re-timing a column

Re-timing means getting the column off the room and re-meshing the racks on the spur gears. Lippert's TI-177 covers the removal: room out until about 8 in is still inside, the room supported on a floor jack, a 2x4 on edge on top of the room between the T-molding and the sidewall, motor unplugged, the column's caulk bead cut and its screws out. Then a jumper from a spare harness to a drill battery runs that motor to walk the column away from the wall.

On the bench, the timing itself follows the assembly manual: slide the notched end of each rack onto its bearing block shoe until the spur gear engages, turn the torque shaft by hand until both racks sit at the start of the gear, and press down on one rack. Both should move together. Center the column without covering any rack screw holes, reinstall the motor, then measure from the column to the end of each rack: the numbers must match.

Reinstall per TI-177: OEM sealant down the H-column's inside edge, the lower rack's lip tight to the bottom of the room, and each rack set to the center-to-center spacing you recorded before removal so they stay parallel and square. Screw the column by each rack and in the middle first, then the rest. Resync when both sides are done.

Careful: Before you loosen a column, support the room with a floor jack and set the 2x4 as Lippert specifies. Once the column screws and racks are loose, that side of the room can drop or roll.

When it's a column replacement

If the shoes are damaged, racks are gouged, teeth are broken or bearing block rivets are sheared, re-timing won't last. Lippert's TSB 146-001-2022 (now revision C, August 2024) covers inverted gear rack systems built about October 2021 through January 2022 with guide shoe damage. It requires inspection first: obstructions, damaged wiper seals and out-of-spec measurements have to be fixed before the kit goes on. Only inoperable or jammed systems are replaced, and both sides get replaced together.

Order by the variant tag on the H-column and the rack profile (standard or inverted; Lippert's QR-078 compares them and QR-158 covers ordering standard racks to replace inverted). Individual parts from the TSB kit include spur gear 238893, V-roller 292801, upper bearing block 299076 and lower bearing block 299075; Lippert also sells bearing block kit 379060.

On the job

  1. Look at both ends from outside: one end ahead (sync), or the top and bottom of one end different (time)?
  2. Sync: check voltage at the controller, then run Lippert's resync and confirm both motors stop together at both ends.
  3. Still crooked: measure column edge to rack face at all four corners, full out and 3 in from closed, and check parallel.
  4. Inspect racks, shoes, spur gears and V-rollers for gouges, broken teeth and debris.
  5. Out of time with clean parts: support the room, pull the column and re-mesh the racks.
  6. Damaged parts: order by the variant tag and rack profile, and check for an open TSB.
  7. Resync after any column work, then measure again.

Numbers

Shop tip

Photograph the variant tag and both ends of a rack before you call for parts. Lippert's parts people need the profile and the notch, and a wrong guess means a second order.

Where this comes from