Dometic Heki 4 drive shaft failure

danielmccoy

2004 Sprinter Westfalia
Yesterday I attempted to open my skylight to adjust the antenna on the roof. As the skylight was attempting to open, in sub-freezing temperatures, a grinding and crackling noise started to come from the left side. The skylight did not open completely. I immediately stopped it and tried to lower it. That did not work either. It was stuck 1/4 open. Freaking out, I attempted to figure out what was wrong. Eventually (after taking the four plastic pins out of the hinges on the exterior) I discovered that the left driveshaft had come unwound. The driveshaft is a steel cable inside a plastic sheath (see photo). I am assuming that the skylight might have been partly frozen to the seals, causing extra resistance. Luckily, I had spare driveshafts that I recently acquired (otherwise it would have cost £92.88 from Leisure Parts Direct). The driveshaft is easy to replace, it just slips on both the gearbox and the mechanical lift (grey box).

I would urge you all to do routine maintenance on the Heki 4, including:
  • Vacuum out all the bugs that inevitably die up there.
  • Spray silicone or PTFE-based spray on all the hinges and the mechanical lift (the grey boxes that contain the screw-type mechanism). After doing this, the skylight went up noticeably quieter. Try and apply some of this inside the driveshaft (where the plastic sheathing and the metal ends join).
  • Apply 303 Aerospace protectant or Armour All to the gaskets for their protection.
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Fredb

Member
danielmccoy... good advice.

Curious... the driveshaft on Left side ... as you face the front?

Have been wanting to do this as my skylight has been 'creaking' for a while, but have been unsure how to get at the parts that require lubrication. Can you provide any further description to the steps involved in getting to the point where you can do the recommended maintenance.

Thanks in advance for your help.

(Otherwise, anyone familiar with a thread on this forum that reviews skylight maintenance and/or removal?)
 

danielmccoy

2004 Sprinter Westfalia
danielmccoy... good advice.

Curious... the driveshaft on Left side ... as you face the front?

Have been wanting to do this as my skylight has been 'creaking' for a while, but have been unsure how to get at the parts that require lubrication. Can you provide any further description to the steps involved in getting to the point where you can do the recommended maintenance.

Thanks in advance for your help.

(Otherwise, anyone familiar with a thread on this forum that reviews skylight maintenance and/or removal?)
Fred:

Yes, it was the left-hand side (as you face the front).
For lubrication: open the skylight. stand on the counter. Look at the silver rectangular boxes that contain the screw-drive (both L and R side) that the skylight arm raises and lowers on. You will notice that you can't actually see the screw-drive, and the box has a narrow long opening with a fuzzy-type of weatherstripping (to assumedly keep out dirt and bugs). To lubricate that screw-drive, use a spray nozzle that has a straw. Insert the straw into the grey rectangular box that contains the screw-drive. Though, you need to angle the spray so that you are actually hitting the screw-drive, which is located on the inside of the grey, rectangular box, rather than straight down. Lubricate both sides, all along the screw-drive. Also, try and force the straw between the black sheath and the metal drive shaft (see the previous photo). You will see where the shaft connects outside of the grey boxes. Again, only use silicone or PTFE spray-type lubricants.

Then, on a ladder, lube all 5-6 hinges that are located on the front of the skylight. I also took the time to tighten the screws that hold the hinges to the roof (some of mine were loose). Also, clean (with a vacuum) the dead bugs out of everything up there (maybe before you lubricate?), and also protect your gaskets with Armour All or 303. Good luck!
 

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