Intro

Both the 213 and the 496 MHU share the same type of bearings, read more about replacing the MHU bearings

There are several types of masthead units, when one of the connectors is corroded try these:
 
Farnell order code AMP code omschrijving
170-4271 205841-2 Circular Connector
155-6944 1-206062-4 Cable Clamp Kit
593-242 1-66506-0 Crimp Pin Gold 24-20 AWG (per 10 stuks)
(this info is for the Vertical MHU,thanks to Wim)

213 Horizontal Mast Head Unit

This is the common MHU.
 
Pin layout Horizontal MHU:
         _
   H - A - B
G - K - J - C
   F - E - D
 
 A  Black  0V supply
 B  Screen  Screen
 C  Red  Wind angle phase (Red)
 D  Orange  +6.5 V supply
 E  Screen  Screen
 F  Green  Wind angle phase (Green)
 G  Blue  Wind angle phase (Blue)
 H  Violet  Wind speed signal
 J  --  No connection
 K  --  No connection
 
You can test the cable only by shortly connecting the violet to black, this will create a wind speed pulse, do this a few times quickly to test the windspeed displays.

496 MHU

   3
2    4
   6
1    5
 
1 Violet Wind speed signal
2 Orange +12V supply 
3 Blue Wind angle phase (Blue)
4 Green Wind angle phase (Green)
5 Red Wind angle phase (Red) 
6 Black 0V supply

Broken parts

The part was made with acetal (not sure if that is the English name) is similar to Teflon but it absorb less water so don't change in size over the time.
It was made in a friend lathe, sorry but I didn't note the measurement, but at least with pictures give an idea of how repair it instead of buying a expensive B&G arm. For sure showing pictures to a lathe operator can do something similar. The lower side is glued to the body (bearing house) and the upper side is attached with two little screws, just making pressure on the body, no need to drill it. Internally there is no mechanical join between parts, the anemometer move a kind of magnetic disc witch the sensor "read" from the internal upper side. The only care to have is that the disc need to be near enough to be readed but not as much as touch the upper body and get any kind of friction.

Thanks to David Monagas for the tips