GMC Western States

 Tech Center Number 3 - October 1992


Thanks to Ed Burner for his Electrical Basics contribution in the last issue of Tech Center. Thanks to Alan Singleton for letting us reprint his Window Channel Replacement notes.


Parts Update

The following is a press release which was read at the Mount Hood Roundup:
OM Service Parts Operations and Cinnabar Engineering expand license agreement.
Detroit- On August 24, 1992, General Motors Service Parts Operations (SPO) and Cinnabar Engineering entered into a letter of intent to expand their license agreement to include all parts listed in the GMC Motorhome parts book (except those parts in mandatory service with SPO). In addition, SPO plans to make amiable remaining inventories of these parts to Cinnabar Engineering, which has worldwide distribution centers in California and Michigan.
Cinnabar Engineering has been a manufacturer and supplier of GMC Motorhome service parts since 1979 and took over distribution of the Motorhome service publications in 1986. The expanded license agreement with Cinnabar Engineering restates GMs commitment to support its Motorhome with service parts.
According to Michael Fellberg, SPO' s manager of trademark licensing, the expansion of this agreement will benefit owners of the GMC Motorhome. "There is an enthusiastic group of GMC Motorhome owners who want to keep their vehicles in first-class condition. They require parts support and technical assistance to achieve the full useful life of their Motorhome. Cinnabar Engineering has the resources and expertise necessary to fulfill those needs."
SPO licensed Cinnabar Engineering in 1990 to manufacture and distribute certain obsolete parts for the GMC Motorhome manufactured from 1973 to 1978 by the former GMC Truck and Coach Division, now GM North American Truck Platforms. Under the license agreement, Cinnabar Engineering has been using GM tooling and technology to provide service parts that meet original equipment design specifications.
For more information, contact Cinnabar Engineering, 10836 West Loyola Drive, Los Altos Hills, CA 94024; (415) 948-2618.
Cinnabar already has a number of previously discontinued parts back in production. They include the lower steering shaft, and the grill. Many new parts are coming back each day. Cinnabar needs to hear from GMC'ers, call and let them know which parts you need, reproduction depends on demand.


Window Channel Replacement

1. Getting started
Start on a warm dry day. Banging your cold hands gets to be quite painful. You will need clear area on both sides of the coach-minimum 16 feet wide-or you will have to move or turn the coach. At least four feet of space is needed on the working side. The work area must be well lighted; natural light is preferred.
Before starting the job, take a good look at all of the windows you plan to work on. Look for things that need to be replaced, such as the latches or the plastic screw anchors for the latches. Look for things that must be realigned. The mullion on the sliding pane may have slipped down to where it can drag a corner on the new channel and tear it. You may want to paint the frames with a black semi-gloss paint to give the job a finished look.
The mullion can be removed and repositioned by placing a hardwood block against it and tapping it off the pane with a plastic faced mallet. The pane can be broken quite easily this way too, so if you find it necessary to remove the mullion, work slowly with the minimum effective amount of force.
Proper tools for the job include; a work stand about the height of a picnic bench, long nose pliers, leather punch, short piece of hardwood dowel cut on an angle to clean the frame channel, soft cotton rags, mineral spirits for cleaning, and a vacuum cleaner to clean out the debris.
You will need two 25-foot rolls of window channel to do an entire coach. A 23-foot coach will use about 40-feet and a 26-foot coach will use all of your 50-feet. You may need a small tube of weatherstrip cement. The cement is only needed to tack down the ends of the channel to keep it from lifting.

2. Removing the old channel
The factory installed channel has a steel wire wound in to give it shape. It is held in the frame by the tension of the wire against the frame, The wire is usually badly rusted and the flocking is worn off allowing the pane to rattle around in the frame.
Starting at the top rear corner of the window, grasp the end of the channel with the long nose pliers and pull it out of the frame. It may help to remove the "worm" so you can get under the end. The strip may require a gentle start from the dowel but once started, should easily pull out of the frame.
Cut the old channel close to the pane (pane closed) with sharp cutters so as not to leave the wire bent into the window groove. Repeat for the bottom channel.
Slide the pane open as far as possible. If you have removed the "worms' be careful not to bang the pane into the frame. Using the long nose pliers and the sharpened dowel, work the channel out of the groove at the top of the window. Pull the end of the channel past the pane at the top. Lift the channel out of the frame around to the bottom and pull it past the pane on the bottom. Even with the channel removed the pane cannot be removed from the frame.
With a vacuum cleaner, remove all of the rust, dust, and debris from the window frame. Examine the groove closely to be sure there are no burrs in it and that the sides are straight. Wipe the grooves clean with a rag moistened in mineral spirits.
For those who have had their windows "fixed" by some non-GMC repair facility, the hard part begins. You will probably find the wrong type of channel installed with lots of weatherstrip cement to make sure it doesn't leak. The weep slots in the bottom of the groove will be plugged. It is absolutely necessary to get all of the garbage out of the groove and get the weep slots clean. Use the sharpened dowel for a scraper and use a rag dampened with mineral spirits or a weatherstripping cement remover to get the old cement out. Don't let the solvent drip through the weep slots onto your coach, it will soften the paint!

3. Installing the new channel
You will need a pair of heavy duty sharp scissors or snips to cut the channel, a 1/8" or 3/16" hole punch, and some white chalk. Measure the length of channel required by holding it along side the frame. Do this carefully because cutting too short will waste a lot of channel. If you cut too long you might find you are a few inches too short for the next window. Mark the cut line on the channel with the chalk. Double check the length, leaving an extra inch for minor adjustments. Cut the channel.
Lay the channel along side the bottom of the frame to determine the location of the weep slots. The weep slots on the outside of the frame do not match up with the weep slots on the inside of the frame. With the chalk, mark the location of the inside weep slots on the side of the channel. Indicate the length of the slot. With the punch, make two rows of holes in the bottom of the channel. Stagger the holes and allow enough space between them so that the fabric does not become unduly weakened. The rubber channel will not support slots-they will allow the channel to distort-you must make a series of holes instead of a long slot.
Carefully slide the pane to the closed position. Press the channel into the frame, starting at the bottom rear: Adjust the position of the channel so that the drain holes line up with the weep slots. At the pane, open the channel flat and work it under the glass. A helper to lift the pane and some careful work
with the long nose pliers will help, be careful not to puncture or tear the channel. Slide the pane all the way to the rear. Continue pressing the channel into the frame, compressing it slightly in length as you work around the corners to make sure it doesn't pull up from the bottom of the frame.
When you reach the pane at the top center, check the alignment of the weep holes with the weep slots and make any adjustments. Again open the channel flat and work it over the pane. It will be more difficult here because the pane will be sitting on the bottom of the channel and there will be less clearance. Slow and careful work with the long nose pliers will most likely be required here. Once over the pane, slide the pane to the closed position and continue to press the channel into the frame.
This would a good time to make sure the pane slides smoothly. It maybe a little stiff. Slide the pane all the way open. The top and bottom rear corners should not hit the frame. Trim the ends of the channel and glue in the "worms" to act as stops. You may want to put a small amount of weatherstrip cement under the last inch or two of the channel.

4. Driver and passenger sliding windows
The front sliding windows are the simplest and easiest to do but should be saved for last because they require only short pieces of channel. This is where you use the left-over pieces. Before you start, make sure you have enough to make three pieces for each window.
Remove the old channel and clean the frames the same way you did the large windows. Install the vertical piece in the front of the window frame first. The ends are best left squared off, not mitered. Cut the piece slightly long so it will be compressed when installed in the frame.
Lay the bottom piece along the frame and mark the weep slots as before. Punch holes in the channel, one row will be sufficient. Install the bottom channel next, it will have to be worked under the window as before. Start with the window open so you get a good fit in front.
Install the top channel last, working the channel carefully over the glass. A small amount of cement on the last inch will keep the channel in place,
Enjoy rattle-free and smooth sliding windows. The panes will offer some resistance to sliding which is normal.


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