Read Only Funster
Funster No : 8116
Join Date: Aug 2009
Location: Kidderminster, Worcs.
Interests: Dog Agility
MH Type: Coachbuilt
MH Model: Autocruise Starburst
Years Motorhoming: 19
Thanked 1 Time in 1 Post
Sorry for the long reply, but the following may explain about how Thetford fridges generally work.
I've got a five year old Thetford N80 (Electric ignition). Last weekend I smelt a nasty burnt plastic smell and discovered it was coming from the Fridge outside vent. I took the vent off to investigate and found the fridge exhaust tube terminal very hot and part of the plastic vent trim melted and the inner insect frame distorted from partially melting! I was using Gas as I was on a rally field.
I tried changing the thermostat setting via the front panel knob from low to high. The flame size (about 15mm high and blue in colour) did not change. It appears that the fridge is on full output at all times. How does it all work? I found out via some web sites that I have a single thermostat model. Does the thermostat change the gas flow and hence flame height or does it switch the flame from pilot to full for varying periods depending on how the control knob is set? I decided to get the fridge out next day to see if the control knob has somehow got detached from the gas valve spindle?
I got the fridge out of itís housing by about 100mm to check the spindle was turning and it was. I arranged for the fridge to be repaired by an authorised Thetford engineer at a local Caravan Centre. Their conclusion after discussing the problem with an office based Thetford engineer was that there was no problem and the fridge was working ok. The Caravan Centre could see that I was not happy with the conclusion and gave me Thetfordís Customer Service number to ring. They told me that the plastic vent trim melting and the inner insect frame distorting was normal! Apparently a well known problem! The good news from the Caravan Centre Ė no charge, which I am truly thankful for.
I rang Thetford and got the same answer with helpful advice (not) that I should get the fridge inspected every year by an authorised agent. Although it appears that this would not have stopped the vent melting! After much probing I finally got the information that the burner worked in a digital fashion i.e. either full on or pilot lamp. There is in fact a temperature sensor buried in the fridge underneath the gas valve assembly. This is not mentioned in any user manual or parts list/diagram. The burner is full on until the sensor senses that the fridge is down to temperature, and then the burner goes to pilot light. As far and the human eye is concerned the burner has four rectangular slots. When full on, four distinct flames can be seen as they emerge from the burner and the sound is a distinct roar. When on pilot light, one flame seems to sit over all four slots and looks a gentle affair with no discernable sound. I tested the fridge with flame enclosure removed. From a standing start at an ambient temperature of 200C I set the thermostat at 6 (dial dots corresponding from 0, fully anticlockwise to 15, fully clockwise Ė dot missing at noon due to space constraints).
I also put an ice cube tray (filled with water) in the freezer. The burner then burnt:-
on full for 2hr 54mins
then pilot for 27mins
then full on for 27mins
then pilot for 27mins
then full on for 21mins
then pilot for 24mins
before returning to full on and the end of the test. The water in the ice cube tray had turned to ice.
So after all that, the fridge works, but I have no idea why the vent trim and insect screen melted. Iíve learnt that due to the total lack of information on how the fridge works in the user manual, I assumed the fridge was not working properly when the control knob did not control the burner flame.
Why do manufactures no longer treat the customer as being intelligent and insist on not giving information on how the fridge works. So that we provide annual service work for their agents? In this instant that back-fired, their agent wasted their time to find out the fridge was working ok.
What will I do next? I will remove all un-necessary plastic from the upper vent frame and fit an extra piece of aluminium deflector to ensure that the upper vent frame is protected from the exhaust. I will also do what Thetford now apparently advise (I didnít know, I wonder how many others donít) that the insect screens be removed when the fridge is in operation!