Replacing Thule Omnivent touch Control

[Riverbankannie]

Our Omnivent is giving the dancing led lights. After switching on the fan runs for a few seconds and then the 2 outer leds flash in turn.
According to the manual, this is “motor blocked”.

However himself has dismantled the motor, checked the brushes etc and all the things mentioned on other forums. We have also connected it directly to a spare 12v battery and the motor runs the fan easily and quietly in both directions (if a bit too fast!).

We are unwilling to fork out the £80 plus for a new controller as by all accounts we read (admittedly people only post when there are problems), they fail again quite quickly.

We have a 2015 version with a sealed pcb and don’t think it was damp getting in.

Considering replacing controller with simple rocker on/off, in/out switches but thinking we also need something to cut down the speed of the fan by using resisters? The motor has 12v stamped on it but as I said, when running directly from the battery it nearly takes off !

Anyone done something similar or can help with what bits to get please
Thanks in advance.

 

[Riverbankannie]

We want to make the equivalent of this old style controller but 2 speed would be sufficient.
I know some of you out there are good at drawing wiring diagrams. Can anyone make one using this spaghetti as a guide.?
@autorouter @DBK @pappajohn off the top of my head!

 

[DBK]

You could connect the two resistors in series then have simple on/off switches to short them out in turn. There would also be a third switch which disconnects the supply. So you would end up with a line of three switches, with say the one on the left as the basic on/off and the other two each shorting one of the resistors. By shorting I mean the switches are connected to each end of the resistor. When open the current has to flow through the resistor, giving a slower fan speed. It might be logical to mount these speed control switches upside down so when the fan is not being used all the switches are in the "up" position. Then you progressively flick them down starting from the left to get increased speeds.

A bit of trial and error needs to be done first as if the fan is too fast when connected directly to the supply then you could dispense with one of the switches and just leave that resistor permanently connected.

If you want to be able to reverse the motor you would need to add a suitable double pole switch to change the polarity. If you Google "DPDT switch" you will find some hints on how to do this and what sort of switch you need - it will probably have six terminals and be wired like this:

 

[Riverbankannie]

Thank you John. Yes we are currently in test mode on dining room table with occasional visits to garage for the 12v battery ! He currently has 2 resisters and 2 switches from old bits found in garage on a test rig., will get better looking switches if works ! And will have to get a DPDT switch tomorrow
Missing the old Tandy store we had locally and of course all the closed Maplins all over Bristol.

 

[DBK]

I should have mentioned this an inefficient way of controlling speed as you will be wasting power in the resisters. I guess the original controller probably uses something like pulse width modulation which is much more efficient. If you have a multi-meter you could check the current on different speeds. There may not be much difference.

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[Riverbankannie]

I should have mentioned this an inefficient way of controlling speed as you will be wasting power in the resisters. I guess the original controller probably uses something like pulse width modulation which is much more efficient. If you have a multi-meter you could check the current on different speeds. There may not be much difference.

Yes, we had thought that this was the way the new PCB Controlled speed. The old resisters get warm very quickly in our test rig and we are unsure about putting them between the headlining and the roof.
Do you think it is possible to buy a small controller just to do this job. What would I Google?

 

[DBK]

"12 volt dc motor speed controller" throws up several links at around £10 but you would need to look at the specs to see what the current ratings are.

 

[DBK]

Forgot (again) to say make sure the controller is for a motor with brushes. Brushless motor controllers are very different.

 

[Riverbankannie]

Beginning to think I might as well just buy a replacement one but HWMBO is convinced by his switch idea!

 

[Riverbankannie]

I just floated the idea last night and let it rest. This morning, he suddenly says, you might as well go ahead and order a new one !
I softened the blow by saying he could use the old one to take apart and still try and build a rocker switch replacement on its frame
Good idea, he says.

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[DBK]

I just floated the idea last night and let it rest. This morning, he suddenly says, you might as well go ahead and order a new one !
I softened the blow by saying he could use the old one to take apart and still try and build a rocker switch replacement on its frame
Good idea, he says.

I think that's the best solution too. I was a bit worried about the potential fire risk from the resistors - and insurance companies might be reluctant to pay out if the damage is caused by an unsafe modification.

 

[Riverbankannie]

I think that's the best solution too. I was a bit worried about the potential fire risk from the resistors - and insurance companies might be reluctant to pay out if the damage is caused by an unsafe modification.

We are worried about that but would build some sort of protection in. The old style controls for the omnivent are those I pictured above so I imagine they are still in use in plenty of caravans and MHs.