I'd think that you would need a quality milliohm meter to check for resistance at that point, an IR thermometer or a finger on that area would work better to sense where the issue is.
Edit:- if you have easy access to that area, maybe try to connect a second heavy earth lead to that point and check to see if doing that reduces the temperature at that point.
Another Edit:- maybe better to check the voltage between that stud and a good local earth point, before and after applying a 2nd earth lead.
Thank you for this, I tried measuring the resistance at various points on the PTC heater and struggled with my standard multi meter as the resistances were less than 1 ohm.
I was surprised to see the heater I have below:
Mostly black plastic - feels very flimsy - and also has the SAME OE number as other alloy PTC's I have seen.
So VAG have updated to this with the SAME OE number!
And the latest C number is from Valeo looks like this:
The plastic arround the earth terminal has started to degrade - so has obviously got hot!
It is brown plastic on mine - and black on these later versions - maybe a better/more suitable grade?
Tried measuring the resistance between the large brown cable and the ring terminal and got arround 0.3 ohms.
Does this seem reasonable? Or is my measuring flawed/not accurate enough? I think this is flawed method for measuring resistance in high current cables.
Also tried measuring resistance between earth cable and earth terminal on heater - again I think beyond the accuracy of my multi meter,
I should probably do a voltage drop test over this cable/terminal - trouble is I can't control when the PTC heater turns on.
This is the resistance of one of the 3 PTC circuits in the heater - each was arround 0.8 ohms.
any ideas?
Thinking of just getting a later PTC heater of ebay and see how that works.