Results 1 to 6 of 6
  1. #1
    ukcommando's Avatar
    ukcommando Guest

    Hotpoint Mistral Thermistor Problems



    I've just replaced the freezer and evaporator thermistors in my Mistral Fridge/Freezer to fix the common problem with loss of cooling in the fridge (as described at length on many other threads here)

    I thought I'd take the opportunity to measure the resistance of the old and new thermistors to see if there was any hint of which was at fault. The values I measured (at room temperature) were:

    Yellow (evaporator) Old 3.7kohm New 4.34kohm
    Green (freezer) Old 3.7kohm New 3.7kohm

    This does make me wonder if it was the yellow thermistor at fault in my case. I know that this is a rather simplistic test, but it would be interesting to see if anyone can corroborate with their own readings. Has anyone else had the opportunity to do measurements like this? Reason for asking is that if the repair can be limited to replacing just the one component rather than two, it all helps, especially considering the rather low value of second hand fridge/freezers anyway.

    Cheers

    Dave



  2. #2
    Brian_UK's Avatar
    Brian_UK is offline Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
    Join Date
    Mar 2001
    Location
    Dorset
    Age
    76
    Posts
    11,192
    Rep Power
    60

    Re: Hotpoint Mistral Thermistor Problems

    Dave, you could well be right.

    It doesn't take a lot to confuse the controls when a sensor starts reading incorrectly. Depending on the type of sensor then the temperature offset from that expected can be quite large.

    A set a tables from Honeywell, here....

    http://content.honeywell.com/sensing...ancetables.asp

    can show the different temperatures against resistance.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

  3. #3
    Join Date
    Jul 2007
    Location
    Australia
    Age
    50
    Posts
    1,855
    Rep Power
    20

    Re: Hotpoint Mistral Thermistor Problems

    Plug the sensor in, turn the fridge on and compare volts.
    I repair a certain brand which has thermistors failing a lot. Sometimes it shows up when reading resistance, but a lot of times it doesn't, it only shows up when plugged in and reading the voltage across the thermistor.

  4. #4
    daveflower's Avatar
    daveflower Guest

    Re: Hotpoint Mistral Thermistor Problems

    the problem isn't with the sensors, but with their connection on the rear wall of freezer, moisture builds up during defrost cycles and corrodes connections to the point where they build their own resistance, and thus changes the reading the pcb gets, and therefore affects the operation of all components. You can try cleaning the contacts, but in my years of experience it never works for very long. It is far better to replace both. Latter units featured covered terminal blocks to shield from moisture deposits during defrost.
    Hope this answers your question.

  5. #5
    stan4928's Avatar
    stan4928 Guest

    Smile Re: Hotpoint Mistral Thermistor Problems

    I have just checked the door on my fridge compartment and noticed how much the door had dropped, and then fridge started up! I going to run it for a while to see what happens to temp, and will post an update. If its a case of adjusting door hinges will keep u posted...

    Dave M

  6. #6
    stan4928's Avatar
    stan4928 Guest

    Re: Hotpoint Mistral Thermistor Problems

    Over the moon, it was the problem with the fridge door that had sagged enough from the push switch which kept the light on when the door was shut, where the temperature went upto +22. saced myse;f money as i was about to get on the phone and but 2 thermistors. I read a small thread from another fridge problem and that was the same problem as mine. Misatral Plus is working perfectly and saved me a fortune!!!
    It may be the same with other problems i have seen on these thread? Sherlock and Watson would have been impressed!!
    Bye for now over the moon (sad i know) but relieved!!

    Dave M

Similar Threads

  1. Hotpoint Mistral evaporator fan
    By 200dan in forum Domestic
    Replies: 12
    Last Post: 18-10-2010, 09:02 PM
  2. Hotpoint Mistral Plus
    By Bobby Ewing in forum Domestic
    Replies: 5
    Last Post: 05-01-2008, 12:35 PM
  3. Replies: 7
    Last Post: 06-09-2007, 02:53 PM
  4. Hotpoint Mistral Plus playing up. HELP! please
    By AJ52TOY in forum Domestic
    Replies: 6
    Last Post: 04-05-2007, 09:35 PM
  5. Hotpoint Mistral Fan problems :<
    By Johnthechef in forum Domestic
    Replies: 10
    Last Post: 04-06-2006, 04:03 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •