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I have a Mk1 Golf Cabriolet with an hydraulic roof. Today I went for a drive and whilst the roof lowered as normal, I could not raise it again.

I checked the fluid levels and they're fine.

There is no sound coming from the pump at all. The only sounds I can here are from a bank of 3 relays.

One relay triggers when the up button is pushed, one when the down button is pushed. I am unsure what the 3rd relay does as it makes no noise.

I unplugged the pump and connected a multimeter to the socket it connects to and got 9.5 volts (car engine not running).

So, there seems to be power coming to the pump but nothing is happening. What could be causing this?

Any ideas would be great!

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    9.5 V seems low. I would expect at least 12 V (assuming it isn't low by design).
    – dlu
    Jul 24, 2016 at 4:15

2 Answers 2

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I'd suggest one of your relays has gone astray. You can test this fairly easily by swapping out relays, if they are the same. Just remember which order you have them in originally, and exchange them one for another. This will help you determine which relay is bad and should also allow you to get the top back up for the meantime.

It could very well be the third relay which you talk about as having the issue. I'd try to replace it with one of the other two which is making noise and see if that doesn't temporarily solve the issue.

You can also manually test the relays. A typical four pronged relay should basically have two prongs which energize the relay, then the other two will have continuity when the relay is energized. If you aren't getting continuity when you energize the relay, then it's bad. Since I don't know the exact design of the relay, you'd have to research this.

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This turned out to be due to a bad alternator hurting the battery. I've replaced the alternator and it's working again.

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