D40 heater not working

[brian0307]

Hi guys I have an 07 navara d40 diesel
The past couple of weeks I've noticed heater not working. Air con works fine on cold but no hot air ( very minimal). Also the fan speed dial only working on 2 3 &4...1 doesn't even switch on. If driving with heater off & letting air into cab it gets hot but once I turn heater on it goes cold again just wondering if any one has had this problem before ?

 

[Old.Tony]

The fan speed issue is easy - failed resistor pack. Don't buy from Nissan, someone from here found one at something like a quarter of the price or less. Don't get ripped off, but that's one part of the problem.

The heater issue might be a door problem - if muck has jammed the inner air path doors (they're all run by servo motors) then it's possible that you're not getting air flowing over the heater matrix and then into the cabin. That might mean disassembly of the air ductwork is required. Another possibility is the coolant flow through the hoses. Heater matrix is the next step from the EGR cooler on the front of the engine, so you should be able to easily check and see if there's any flow through that.

 

[justbruce]

I don't know if something is wrong or not.
Over the past few days I have done quite a bit of 4wd'ing on the bitumen. (Actually on the ice and snow on the bitumen.) The demister going flat out so I can see where I'm going. Whenever I pulled over for a few minutes, idling, the fan would start blowing cold air. The temp gauge would drop about a needle thickness. This would also happen when going easy in 3rd and 4th.
As soon as the engine started doing a bit of work, everything returned to normal.
I was thinking thermostat but, the temp gauge doesn't move any other time.

 

[Old.Tony]

It would be very interesting to find out what your actual temp is. I've found that my gauge doesn't really start moving until it's over 50C, and it's a third of the way up at 90C. It barely moves for the next 10 degrees up and then at 110C it hits halfway. I think it's about as accurate as having a blind man as a navigator in a rally car.

It does sound like the thermostat is closing on you due to the cold.