intermittent wipers nor headlight wipers work
 

(1987 420SEL) All windshield wiper positions work except for the intermittent one. Also, if you try to clean the windshield, the wipers don't come on, all it does is just spray. Same with the headlight wipers, the lights will be on, then when I push the wash button, nothing happens down there either!
I have searched and heard someone mention a combo switch relay? What number is it in the fuse box if it is there and if so, can this fuse be repaired similarly to the fuel pump relays? Is there some other fuse that affects intermittent wipers?
Thanks
David