Rear wiper motor problem

Hi' folks i have a problem with my rear wiper motor it started off with the front wipers stopping on the front screen then when i engage the rear wiper the front wipers start working again then again stop.

I replaced the relay now the front wipers stay on when i put ignition on and will only stop when i engage the rear wiper then the front wipers swipe 3 times then rest.

Now i have replaced the rear wiper motor because when i take the plug out of the rear wiper motor the front wipers work fine.

What's happening now is when i turn the ignition on the front wipers are now swiping 3 times then rest i have returned the rear motor which is a non branded motor from ebay has anyone had this problem.

Thanks