Dometic Heki 4 drive shaft failure

[danielmccoy]

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.

 

[Fredb]

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]

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!

 

[Fredb]

Daniel... thanks very much for the follow-up explanation. Very helpful.

 

[Wasaabi]

I just overhauled our Heki 4 skylight.
- Took the inner frame off. Removed both of those screw shaft units that control the roof and cleaned out and re-greased the internal screws.
- Took the two drive shaft cables off and sprayed the inside with silicone spray.
- Reinstalled them and set them so that are at the same height (used a caliper to measure, turning both screw shafts to same spot).
- Tightened the shade rolls for the screen and sunshade.
- Stuffed some foam in the screen/shade connection handle to hopefully stop it from snapping apart mid-ride.
- One of the plastic sliders that pulls the shade was so warped from heat, but I fixed that with a heat gun, getting it hot enough carefully to then easily bend it back to where it should be.
- And finally, for those that didn't know, I moved the florescent bulbs to be side-by-side facing the kitchen for better kitchen light (90 degrees from original location). All the extra wire length and prep for this is already in the Heki -- it's cleverly designed in that way.

Now -- here is my question: I am still getting a loud gear/motor noise from the center of the roof upon lifting. I am wondering if anyone has experienced this. The motor looks fine, and I am wondering if it is the gearbox internals, and if that maybe needs to be cleaned and re-greased. I know that the drive cables and screw shafts are working well, and the noise is coming from the center. Any ideas?

 

[WestyTat]

We had the loud "gear slipping" noise before one of the drive shaft failure. If one of drive shaft fails, usually while operating skylight, it will brake/crack the skylight dome. The drive cable will look fine until that very moment. Because it is in sturdy plastic casing it is very hard to tell the status of wires inside.

 

[Wasaabi]

Thank you for the insight. So presumably it sounds like the shaft would look fine from both ends, but somewhere inside is a potentially frayed cable end or two that keeps snagging? Perhaps that is why I hear a repetitive sound. However, it does sound like it is coming from the middle where the motor is and not the cables. The drive cables turn freely in the housings with no noise when they are removed. Does this echo what you experienced?

I will probably replace them but they are annoyingly expensive for what they are. So I’m just trying to be as sure as possible that’s the issue. Thanks.