Help on 633 wipers

I have a 1980 633csi with wipers that will occasionally not respond to the switch on the steering column. After not working for ten minutes, they will suddenly start up again and work normally. I cleaned the
contacts to the motor, replaced the fuse, took apart the motor, replacing both wires to the brushes, and also the ground coming off the connection. I took apart the "rotary contacts" at the head of the motor, and cleaned them, and lubricated the rack and pinion gear running the rotay contacts. I lubricated all parts of the assembly with solicone spray. Things seemed fine until the next day, when the wipers quite during a drive, and then after 10 minutes started again.
Help! Is there a relay? I don't see one in the fuse box, and the fuse is fine as the washers work fine when the wipers don't. Advise would be appreciated.
Paul
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I can't be certain with this model, but many have a relay inside the delay unit which supplies the 'normal' operation volts from an NC contact. Does the delay operation work normally?
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When working, the delay seems fine.
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snipped-for-privacy@verizon.net wrote:

On my 85 635CSi this was due to a bad control relay, it's the big black one in the fuse box. But your '80 car will have a difeent wiring layout.
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