Has anyone rebuilt one of these, or come up with a replacement?
It's the "ECU" that provides the intermittent wiping function. The OP doesn't give year/model/version (I guess he/she thinks that we're clairvoyent), but item 25 "wiper switch" (40284309) here is for a US 308QV: https://www.ferrariparts.co.uk/Diagram/Ferrari/308-Quattrovalvole-USA/117-Windshield-Wiper-Washer-and-Horn Everyone seems to have a slightly different name for it - "wiper regulator module" at SuperformanceUK: https://www.superformance.co.uk/308/electrical.html
It is a TEL12C/1 12V Magneti Marelli Fiat part also. https://www.vickauto.com/FIAT-PARTS/FIAT-124/2000-and-131/Brava-Parts/Electrical/Wiper-Relay-Fiat-124-Spider-etc-SKU-20-7376 Image Unavailable, Please Login Image Unavailable, Please Login
I opened mine up .Two screws to take the cap off .It’s a relay coil with points .You can emry paper , clean up the points . On the GT 4 it’s attached to the inner wheel arch easily accessible. I also with wiper function hassle removed the motor dismantled it and cleaned up the commutator with brake cleaner and very light emry paper on the brush faces .It’s a phaff reassembling pressing the bushes back . Once done the wipers work fine . Before the strip and clean up they would suddenly stop or not start .Not start when in the rest position .If I got out and gently nudged them they would run .It was as if the current was not flowing vis a sticky relay ( what the op is enquiring about ) or dirty commutator, gummed up 40 y + motor or dirty brushes . The whole system might just need a strip + clean ? Hope this helps .
Actually it's still available for Russian Ladas. No joke. And ridiculously cheap I purchased one and exchanged the housing with the old Marelli housing to get rid of the cyrillic script on the housing Sorry, only found a source on germany ebay, but at least it provides the original part ID: https://www.ebay.de/itm/110844482170 Best from Germany Martin