alfa certainly loved their electrical variations!!!
nige - i can't see any variants in w/shop manual that have no a/c but do have twin fans!! ...maybe they cocked up the build of your car
alfa1 - there is a variant (early chassis nos.) that has a/c but only one fan, like this:
Early cars with a/c - EarlyCoolingFanCircuit-withAC.jpg
- you should also have the "2-level thermal contact" on your car , i.e. a thermoswitch screwed directly into radiator to assist in controlling the fans on/off (mainly when your a/c is OFF)
When a/c is ON, fans are controlled by the "trinary pressure contact", i.e. a pressure sensor in the a/c circuit that detects 'hot refrigerant'
my car definitely doesn't have this thermoswitch in the rad (i looked for it thinking my car was of early type!). w/shop manual says that design was changed in later cars for the ecu to control the fans directly...& ecu uses the blue temp sensor stuck in top of main engine coolant thermostat housing to decide when to put fans on (which is why i changed this sensor when overhauling my cooling system, which was a bit erratic!)
so...if you can find the thermoswitch like this:
- then you should replace it! sounds like its dead...
one last thing tho'....r u sure your thermostat isn't a bit duff? fans not coming on has nothing to do with t'stat of course, but your fluctuating temp in normal driving is only controlled by t/stat...& they are renowned for going duff!
mine was duff, but my symptom was constantly low temp gauge readings...except when sitting in traffic (which is when i discovered my fans didn't work either). with new t/stat, it comes up to temp & then moves by only small amounts when changing from town/b-road driving to motorway driving (goes up a tiny bit on slower driving, goes down a tiny bit on m/way driving)
so i'd say you need a new t/stat too! (only £28 from ebspares!)