Overheating Only with Air-Con - S16
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  1. #1
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    Default Overheating Only with Air-Con - S16

    Post #1 Hi,

    I have a problem no one seems to have the answer to.

    While driving the 306 S16 without the aircon, the car runs perfectly but as soon as the aircon is switched on, the temp will slowly start to rise until the high speed fans come on. (This temp rise with the aircon will even happen on cold days!)

    Both fans work as they should and always run together, When the aircon is switched on both fans run consistently as they should, coolant is topped up and bled correctly, thermostat is working and there are no coolant leaks.

    Raditator, waterpump, coolant hoses and heater matrix are new.

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    What has got me baffled is that the engine runs as it should (without the aircon) even under the harshest conditions. Sitting in traffic on a 40degree day, no problems but switch on that aircon and the temp will start to rise instantly to 110.


    I am guessing the problem must lie with the aircon system itself rather than the cooling system, but what could it be???

    cheers

  2. #2
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by Katana View Post
    Post #1 Hi,

    I have a problem no one seems to have the answer to.

    While driving the 306 S16 without the aircon, the car runs perfectly but as soon as the aircon is switched on, the temp will slowly start to rise until the high speed fans come on. (This temp rise with the aircon will even happen on cold days!)

    Both fans work as they should and always run together, When the aircon is switched on both fans run consistently as they should, coolant is topped up and bled correctly, thermostat is working and there are no coolant leaks.

    Raditator, waterpump, coolant hoses and heater matrix are new.

    What has got me baffled is that the engine runs as it should (without the aircon) even under the harshest conditions. Sitting in traffic on a 40degree day, no problems but switch on that aircon and the temp will start to rise instantly to 110.


    I am guessing the problem must lie with the aircon system itself rather than the cooling system, but what could it be???

    cheers
    Is 110 on dash equall to 110 at thermo housing.
    Should the fans come on at Hi speed with AC???


    Are the fan blades firmly connected to the motors and spinning the correct way???


    Is there massive airflow through the radiator with aircon on, fans on high???


    Jo

  3. #3
    Real cars have hydraulics DoubleChevron's Avatar
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    Does it have two fans ??

    If it does I bet one is dead. They are usually wired series/parallel for high and low speed if there is two fans. This means in series (low speed), if one fan is dead no fans will work. However one fan will still work on high speed. However to get it to switch on the engine has to get hot enough for the high speed fan to come on.

    The air-con is bypassing this as it turns the fan straight onto high speed by the sounds of it.

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    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by DoubleChevron View Post
    Does it have two fans ??
    .....
    The air-con is bypassing this as it turns the fan straight onto high speed by the sounds of it.

    seeya,
    Shane L.
    And this days speed reading award goes to.....Shane.


    Jo

  5. #5
    1000+ Posts alan moore's Avatar
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    You say the thermostat is working. Did you pull it out and test it? Most of these cars were fitted with an 89 degree thermostat that possibly is not opening fully when the extra heat load comes in via the air con condenser.

    I have always fitted the 83 degree? diesel thermostat to the four late Peugeots that I have owned, (incl a series 2 Mi16 with the same motor as you) and much happier to see the temp a bit lower. This has not affected the fuel economy or running of these cars in any way other than running a bit cooler. Given what money you have already put toward this problem another $30 for a thermostat and seal is not going to make much difference.
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    Hi guys,

    Low speed fans always run whenever the air con is activated, this should keep the engine temp stable. High speed is only ever used when the engine is overheating or air con pressure is too high. In this case, the high speeds kick in because the coolant temp sensor reads over 107 degrees (overheating).

    Both fans are firmly connected and running as they should. Plenty of airlfow through the radiator. Both checked and no problem there.

    Thermostat has been checked and working correctly too. I have no need to change to a cooler thermo as the the engine remains in check even on the hottest days (granted, without the aircon!)

    If any of these things weren't working as they should, I would notice a problem under normal driving (without aircon). Which is why this problem has me stumped
    Last edited by Katana; 28th February 2011 at 02:22 PM.

  7. #7
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by Katana View Post
    If any of these things weren't working as they should, I would notice a problem under normal driving (without aircon).
    I agree with that statement....
    So what is the problem??
    I would not automaticly assume the problem is the AC.
    It may be that the AC pushes the cooling system over the threshold of failure, but is merely a catalyst in the whole scheme of things (just like climbing a hill and over heating, the solution is not to be found in analysing the hill ).

    Have you tested the temp sender and dash guage during both AC and non AC modes with an external thermometer to ascertain you actually have an over heating problem, and its not just the guage showing high readings?? You would not be the first person to chase a problem that does not exist, and trust me, those types of issues are the hardest to fix.
    The time for guessing is behind you and the time for measuring is now here.
    I'd suggest you start with measuring as many of the parameters of the cooling system and the exhaust temp before and after the AC is switched in.
    Measuring the exhaust temp will give you an instant idea about what the state of tune is, just in case switching the Ac on does something weird to the ECU or fuel delivery system.
    I'd also have a second then third look at the cooling fans and airflow in both AC and non AC modes.

    You have not mentioned coolant. I hope you are running the leanest coolant mix you can with the highest concentration of demineralised water.

    Jo
    Last edited by jo proffi; 28th February 2011 at 03:03 PM.

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    Quote Originally Posted by jo proffi View Post
    You have not mentioned coolant. I hope you are running the leanest coolant mix you can with the highest concentration of demineralised water.

    Jo
    I've been running Alfloc 3777 in the pre-mixed 50/50 coolant for years. I understand running a leaner mixture will aid heat dispertion but I'm confident this isn't related to the problem.


    Would it be possible that the extra current draw involved in running the aircon system is surpassing my "earthing point threshold" and causing my sensors to run wild?

  9. #9
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by Katana View Post

    Would it be possible that the extra current draw involved in running the aircon system is surpassing my "earthing point threshold" and causing my sensors to run wild?
    Its a french car. Any electrical fault is possible and probable.


    Jo

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    I know that you said both fans are running as they should but a chap I know once had a similar problem. It turned out that the cooling fan was running the wrong way and instead of drawing heat from the radiator it was pushing it back in as the car drove along thereby trapping hot air and not allowing the radiator to work properly.

    Given that your radiator and other bits are new I presume someone has been playing around with a number of components. Is it possible that some wiring was switched around causing a fan to run in reverse?

    Just a thought

  11. #11
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    Quote Originally Posted by philipjh View Post
    I know that you said both fans are running as they should but a chap I know once had a similar problem. It turned out that the cooling fan was running the wrong way and instead of drawing heat from the radiator it was pushing it back in as the car drove along thereby trapping hot air and not allowing the radiator to work properly.

    Given that your radiator and other bits are new I presume someone has been playing around with a number of components. Is it possible that some wiring was switched around causing a fan to run in reverse?

    Just a thought
    Thanks for the tip although the fans have been tested and are spot on.

    I'm the only person who does the work on my car, so I know what's been played with.

    cheers

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