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  1. #1
    I Now Post Stupid **** Jibberish18's Avatar
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    Default Zetec engine overheats and fans won\'t turn on.

    I have a 2000 ZX3. For some reason my fans do not turn on and the car will overheat if left standing still for long enough. I have to turn on the Air Condition for both of the fans to come on and cool the engine down. I don't really know what it is. I got my Haynes manual yesterday and it gave me some hints but nothing specific to look for or test out. Anybody have any idea why the fans won't come on? I already replaced my thermostat and the first day it seemed like it was fine but for some reason it did again the very next day.

    On a side not I'm wondering why my A/C comes on automatically every time I turn on my vents. Even my heat. and then sometimes when I have my temperature gauge for my vents about 1/2 the A/C will come on only when I switch the vent to windshield defrost but turns back off with everything else. weird stuff man! weird stuff. [img]images/icons/shocked.gif[/img]

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    Default Re: Zetec engine overheats and fans won\'t turn on.

    I have the same exact problem with my 2000 ZX3 overheating and just got a new cylinder head temp sensor I am going to install in a few days when I can find the time. Hope that fixes the problem.
    As for your A/C, it sounds like it may be operating normally (?) It should always come on when you have the defrost selected, no matter what the temp setting is, but won't come on if the fan switch is at 0, no matter what mode is selected. Can you turn it off when in other ventilation selector positions such as vent/floor?

  3. #3
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    Default Re: Zetec engine overheats and fans won\'t turn on.

    You could check to see if fans are operating. 12Volts across the fan and they should spin. I had this problem before and it was a fan switch. Follow the wiring from the Fan(s) and it should run through a relay of some sort. I would either test the fan or get them tested. If this doesn't work, I would simply replce the switch that the power wires run to . Both are inexpensive ways to troubleshoot. Also just check for a loose connection. Get the car good and hot and either shut car off and tighten or push all connections. You could do it while the car is running, butI hate working near there with fans spinning. But if you loose fingers while the car is running, its a easy way to tell if the fan started working or not [img]images/icons/smile.gif[/img]

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    Default Re: Zetec engine overheats and fans won\'t turn on.

    The issue here is not so much that the fans are not working, because they both come on right away when the A/C is on, so we know that the relay is working when it gets the proper signal from the PCM.but that the PCM doesn't know that the engine is hot so it doesn't turn the fans on. I still have not been able to replace my CHT sensor to see if that fixes the problem.

  5. #5
    I Now Post Stupid **** Jibberish18's Avatar
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    Default Re: Zetec engine overheats and fans won\'t turn on.

    As for your A/C, it sounds like it may be operating normally (?) It should always come on when you have the defrost selected, no matter what the temp setting is, but won't come on if the fan switch is at 0, no matter what mode is selected. Can you turn it off when in other ventilation selector positions such as vent/floor?
    <font size="2" face="Verdana, Arial">The A/C light comes on right away when I turn on my vents. I'm pretty sure it comes in either way even if I have the temperature as hot as possible. I have to manually turn it off. Also if I have the temperature to about half way and I have it on VENT the A/C light will not come on. BUT if I have the temperature up to half way again and I put it for front windshield defrost the A/C automatically comes on. I didn't know if this was normal but I figured after a certain temperature setting the A/C would come on automatically. Just a bit confusing and I never encountered something like this.

    As for the overheating it still does it. [img]images/icons/frown.gif[/img] Once you replace the cylinder temp sensor let me know if it fixes the problem. Maybe I'll replace it myself. I'm also thinking that in a rare case my belt and tensioner may have something to do with it.

  6. #6
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    Default Re: Zetec engine overheats and fans won\'t turn on.

    Noticed the same thing happening to a friends hatch. Idle got the car in the red, with coolant near boiling it seemed.

    She brought it in under warranty, I beleive the service order referred to replacement of a resistor or something along those lines. I'll find out what the SO said, and if there's a part # on there for what got replaced.

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    Default Re: Zetec engine overheats and fans won\'t turn on.

    The A/C should always come on with the selector at the defrost setting, regardless of the temp setting on the dial. The A/C should not come on "automatically" at a certain temp setting, regardless of where the vent selector is at.
    As for the overheating, when my car first started overheating I started by looking for a thermoswitch screwed into the radiator, which the Zetec doesn't have, but found a "device" in the fan housing, at the top of the rediator, between the two fans, with two thick wires connected to it. It easily pops out so I removed it, thinking it was some kind of a temp sensor. It has a metal housing with a wire coil (some kind of resistor?) and what look like diodes inside the metal housing. It looks like it was made to handle high temps/currents but I haven't been able to figure out what this device is-if it's a part of the fan control circuit. I posted about this quite awhile ago but didn't get any informative replies about it. Does anyone have any info on what this is and if it even has anything to do with the cooling system?
    Anyway, I am going to replace the sensor tomorrow and will post the results.

  8. #8
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    Default Re: Zetec engine overheats and fans won\'t turn on.

    I went to replace the CHT sensor and its basically impossible to remove it with the JRSC manifold installed. I did some test resistance measurements of the new sensor in cold, warm, and then hot water, and did the same with the one on the car and it is about the same so it looks like that isn't the cause of the fans not coming on. It really is only an issue when I am in stop and go traffic, when at speed the temp stays at normal level. I just have to remember to keep an eye on the temp gauge and turn on the A/C when creeping along on a hot day.
    I took another look today at the relays for the fans; the A/C fan relay works fine but I took the other fan relay out and ohmed it-the primary coil seems OK and when I popped the cover off that relay, no burned wires or contacts were seen. Both fan fuses were good as well. I will next put two test wires on the primary coil for that relay and when the car starts to overheat again, I will see if it is getting 12V to the relay.
    Anybodys help/advice on this problem is greatly appreciated!

  9. #9
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    Default Re: Zetec engine overheats and fans won\'t turn on.

    i had that same problem a few months ago....and also turned on the a/c and both fans turned on...
    took it in....under warrenty, and found that my heater fan relay switch was blown..

    or the relay that turns the fans on when the engine needs them.

  10. #10
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    Default Re: Zetec engine overheats and fans won\'t turn on.

    Hey Jibberish18;

    I have an '03 ZTS and the washer fluid reservoir is in my left front quarter panel. The only thing I see is the cap. It's between my battery and the quarter panel. Don't look for the big plastic jug, its not there.

    -Jeff

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    Default Re: Zetec engine overheats and fans won\'t turn on.

    jibberish18, thanks for the info. I have thought about replacing the fan relay, but I hate diagnosing mechanical problems by replacing parts-I have done enough of that in the past!
    Whats confusing me about this whole cooling thing is, just what is the device mounted in the fan housing just above the fans, the one with the metal cage around it and the coil (resistor?) and diode or resistor inside the metal cage? The plug attached to it has two heavy gauge black wires. It looks to me like it definitely has something to do with the fans, but maybe I am thinking too hard about this!

  12. #12
    I Now Post Stupid **** Jibberish18's Avatar
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    Default Re: Zetec engine overheats and fans won\'t turn on.

    Hey Nordy200. Sorry haven't replied back in a while. I haven't had much time to look into this problem (family issues) but when I was at the mechnanic getting it checked out the fans actually came on a few time without my A/C engaged. Typical car.....works with you in front of a mechanic. My brothers girlfriend also has a 2000 Zetec and her engine overheats as well. Same exact problem. So I'm gonna check the relays in the fusebox and fuses. I'm actually missing a few (previous owner) and I ran codes at Autozone and it showed nothing. It's possibly a loose connection or some kind of resistor?

    On a side note.....I can't find my Windshield Fluid Reservoir! Where the hell is it (it's not right next to my air box....I have a ZX3 btw.

    And on another side note...I changed my spark plugs and found out that the previous owner had Splitfire V-Crap Plugs in their! Ewwwwww!!! [img]graemlins/thumbdown.gif[/img]

  13. #13
    I Now Post Stupid **** Jibberish18's Avatar
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    Default Re: Zetec engine overheats and fans won\'t turn on.

    I have an '03 ZTS and the washer fluid reservoir is in my left front quarter panel. The only thing I see is the cap. It's between my battery and the quarter panel. Don't look for the big plastic jug, its not there.
    <font size="2" face="Verdana, Arial">Well mine isn't their. I don't know if hatchbacks are the same but I can't find mine at all. LOL. I think it's in the trunk?

    And Nordy200 don't stress yourself out too much. I don't see any other way of figuring this out other than A) Trial & Error or B) Taking every sensor/relay/resistor and testing it's voltage/ohms blah blah blah. Either way you look at it....IT SUCKS.

  14. #14
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    Default Re: Zetec engine overheats and fans won\'t turn on.

    According to the hayes manual

    The radiator cooling fan is controlled by the engines PCM acting on information received by the cylinder head temp sensor where twin fans or two speen fans are installed. Control is through a resistor assemblysecured to the top of the fan shroud. This can be replaced separately if faulty
    THAT WOULD BE WHAT YOUR TALKING ABOUT AND THAT WOULD BE THE RESISTOR THE OTHER GUY WAS TALKING ABOUT HE HAD REPLACED UNDER WARANTEE I THINK I WILL GET A NUMBER ON RESISTOR AND REPLACE IT AND SEE IF THIS IS THE PROBLEM

    I replaced the cooling fan relay 1 and made no diff

    Ill tell you if it fixed it or not as soon as I get to it
    which will be hopefully by the end of this week LOL <font color="blue"> </font>

  15. #15
    is THE most interesting man in the world! airforcefocus's Avatar
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    Default Re: Zetec engine overheats and fans won\'t turn on.

    Here was my overheating issue&gt;&gt; http://www.focaljet.com/ubbthreads/s...o=&amp;fpart=1
    Usually, when the fans don't turn on, it winds up being the resistor pack.


 
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