Originally Posted by Nickplus4
Hi there,
So looking at that track and diode it does look like you have a similar problem as I did with the heater fan motor. My diodes failed to a short, so caused a fuse to blow each time. I assume that a fuse blew when you lost some of the functions? Did you try a larger fuse? Or was it quite a high current fuse anyway? That diode failing and a decent current through that track could have blown the track. I suggest just checking the resistance across the diode (check with the probes the right way round so that you are not forward biasing the diode) - it is in parallel with the relay coil so you will get quite a low resistance if all is well, or a dead short if it is blown. If it is blown you could try replacing it with a common or garden 1N4001 and fix the track with a bit of wire.

I'm not sure if you still have heater fan issues? I would ensure D6 and D7 are also changed at the same time to prevent that issue raising its head.

What I don't understand is why this only affects some cars and not others - unless it is to do with the a voltage regulator or somesuch.

Very useful, thanks for posting Nick thumbs

Re, why this affects some car and not others. It appears to me that the heater issue seems to be reported more on cars with this later style of dash pcb. I believe the older rectangular pcb’s were functionally very similar but a different manufacturer. Also there is the curious addition of two inserted diodes on the later Dashboard connector’s heater high and low pins, see below. Quite what their purpose is I don’t know but I guess they could potentially be problematic? They appear too far from the source to be viable fly back diodes but again I don’t really know, we need a proper expert to suggest what their purpose might be.

[Linked Image]


Dave, dare I suggest a possible test that I might have considered whist the pcb was out of the car, if it were mine? It should be possible to do a heater high/low speed function test along with the heated screen using a link wire on the flying 12 way Dashboard Connector (the one in the pic above).

To test the heater hi/low speed, link the fused (+) supply pin.4 to pins 8 and then 12. And for the heated screen pin.3 and pin.7




[Linked Image]

PS – Warning, as always.... There is a risk that my information above could contains errors so please check yourself first exting

Roger
2011 Plus 4