Bongo Fury

My temperature gauge is very intermittant, works most of the time, then now and again drops down to nothing for five minutes then works again. When i had the passenger side seat up the other day i noticed the bit of gunk on the brass bit in the picture. Is this anything to do with temperature ? Its like hardened resin around the brass but moves around, when its in place it is touching the other brass bit. It would appear that it should probably screw in somewhere as it has a thread. If this is not it any guide on where i might look to sort the temp gauge out please.

https://goo.gl/photos/SAqsew6unTeqYzueA

https://goo.gl/photos/CsYMxMmbf1hWK2pr6

18-510 on this drawing is the temp gauge sender, the other sensor on that drawing is the fan switch.ecu temp sensor but not for the dash gauge, click on the numbers on the drawing then read on the left margin.

http://lushprojects.com/bongopartsmk2/c ... no=.html#4.

this shows 15-17z at the top center of this link. looks like its under the passy seat at the front of the head.

http://lushprojects.com/bongopartsmk2/c ... o=.html#11

the temp sensors are known to get corroded at the terminal wire, clean up and test again, or the sensor top gets knocked or pulled, then the terminal goes wobbly at the rivet, replace with a new one, there only cheap.