-- Sliders can be hard to open or close for a variety of reasons. All of the following should be investigated before ordering a replacement window:

---Clamp ring roll: Radius windows are usually installed using an inside clamp ring. This part is screwed together with the window frame, clamping the wall between them. The clamp rings vary, depending on the wall thickness specified by the manufacturer of the vehicle. This wall thickness must accommodate the actual wall materials, plus whatever sealant is used under the outside window flange. If the clamp ring used is too thin, there will be a gap between the clamp ring and the inner part of the window. The application of the mounting screws will cause distortion of the window frame, resulting in a hard sliding window. This situation can usually be remedied by installing the proper clamp ring.

---Wrong mounting screws: The correct window installation screw for most Hehr windows (other than heavy transit buses) is a #8 X 1/2 in. pan head sheet metal screw, “A” point or self tapping. Use of a longer or larger (thicker) screw will often affect window sliding by distorting the track, which the opening pane rides on. In most cases, this situation is not remediable, and the window must be replaced. The warranty will not apply since the failure and damage was caused by installation error.

---Damage to the window frame: Dents in the frame can cause the slide channel to be pinched, leading to increased slide resistance. Visually inspect the frame surface for any signs of distortion. If distorted, use a narrow block and mallet to gently tap the frame back into alignment. Check slider for improved operation.

---Frame interference: Check for clearance between the sliding pane and the mullion (the bar between the glass panes.) Mullions can sometimes be twisted due to impact, or improper assembly. If the mullion/slider space seems inadequate, try rotating the mullion to permit greater clearance.

---Damage to track: All sliding panes (except heavy transit windows) are captured in a plastic or soft rubber track within the window frame channel. This track can become damaged or distorted and this may cause hard (or no) sliding. Usually, it is impossible to feel down into this track. In order to check for damage, drag a small (1/8") flat blade screwdriver along the top and bottom tracks. Any resistance will result in increased sliding resistance, and the damaged track needs to be replaced. Please see the instructions on glass replacement elsewhere in this manual for track replacement procedures.

---Debris: If the tracks are not properly cleaned upon completion of the vehicle, debris, such as shavings, may accumulate which can impede proper sliding action. This can be alleviated by blowing the tracks out with compressed air, vacuuming out, or with instruments such as tweezers or long nose pliers.

---Oversize window/undersize hole: Proper installation requires that the rough opening size exceed the window size by 3/8ths" in both height and width. If the hole is too small, the window may have been forced into place, distorting the frame , and causing the sliding pane to be squeezed, thus increasing resistance. If this is found to be the case, the window must be removed from the wall, and the rough opening relieved (expanded) to allow an interference-free fit.

---Glass too thick/Track too thin: In rare cases, this can occur, due to improper parts selection at the time of manufacturing. The possible remedies here are: Replace the track with one to accommodate thicker glass; replace the sliding pane (this may cause a color mismatch with the stationary glass), or replace the complete window.