sean65

I came across this post on Instagram, warning that if this relay fails, the vario roof pump will continue to run until it burns out. First time I’ve heard of this type of failure so thought I’d share.

bobterry99

In my engineering career I've never known of a relay to fail in the on state. And if it were to happen in this case, the pump would not burn out in a minute. Or even two minutes. On no account would it "explode".

Still, it may be good to have a plan in the event this does occur. I'd check how quick and easily the pump relay can be removed, since some can be a fuss. It might be easier to disconnect the negative battery cable.

m5zealot

I created this warning. I do have a more detailed account of this in here somewhere. Pulling the relay took 2 seconds - finding a 10mm socket and disconnecting the battery will take longer. 🤪

The relay got stuck “open” so you’re right - it can’t fail while live but it can keep sending current to the pump if the mechanism in there to switch off stops working - so to me that is a fail. I’m not an electrician but I know the pump is not designed to run past the allotment time the control module dictates. The pump was running for about 10 minutes before I realized what was going on. It only took a MINUTE to get to it but as pulled the last cover for it - it had spewed fluid everywhere! The pump was hot to the touch. It obviously does not have self protection and shut off automatically like the pneumatic pump. When I sent it to Tops hydraulics they confirmed the pump motor overheated and “burned up.” It took days and lots of steam cleaning to get the stench out of the trunk. You are welcome. 🤗

elMacko

I assume that the pump motor has a fuse which will break after an overcurrent in the motor is detected..! So, why this didn't occurred before a burnt motor...perhaps is a mystery.

MikeJ65

It has a thermal limit in the control, but that would assume relay outputs not shorted.