Does that information help with further diagnosis?

 

At the beginning of this thread it was pretty clear that you had a thermostat problem. Something people dont like to mention because it is a real challenge to change and most would rather not get involved. The thermostat is hidden at the back of the engine on the driver's side and to get to it you have to remove the windshield wipers and the tray the mechanism sits in. You can then, more-or-less, see the thermostat, but there is at least one bolt that is a challenge.

If the thermostat is stuck open your aux heater will be running almost all of the time, at this time of year - mine was. I changed the thermostat and have to admit the guage does not indicate that much warmer, but the heater does switch off after a while. At this time of year it will always come on initially, but if the thermostat is stuck open it is unlikely that you will ever get enough heat to turn the aux heater off, simply put you are cooling the water very efficiently by routing it through the radiator.

I suggest you bite the bullet and change the thermostat. They are on ebay if you like taking a risk, or you can buy genuine VM parts (made in Italy?) from JNL Engineering, Camberley, for considerably less that Chrysler would charge, I mentioned what I paid before and the same goes for any engine part.

Wiseman Motor Services in Solihull, changed the thermostat for me. They are not a Chrysler shop, but Matthew Wiseman is a good mechanic and can do most jobs on a Voyager in about half the time others would take. On the other hand there are people on this thread that could help such as Richard Ayling who seems to spend most of his mornings tinkering with cars and seems to have more kit than some garages. I dont know if he has changed a thermostat but I bet he would like to try!

Hope this helps