Guest Brett Posted May 13, 2007 Share Posted May 13, 2007 Hi I noticed the other day that my temperature gauge was climbing high and when I checked I noticed that the fan wasn't cutting in. I unplugged the fan connection from the thermo switch and bridged the connector and the fan whirled in to life...so no problems with the fan. I then assumed that it was the thermo switch so went to Fords and purchased a new one which I fitted yesterday but this has made no difference i.e. the car over heated and the fan never kicked in. I've now had to re-bridge the connector again but this means the fan is always on whilst driving (not a problem other than the noise). Is there anything else which can affect the temperature sensor or would you agree with me that the new thermo switch is perhaps faulty ? Any advice appreciated. Rgds Brett Link to comment Share on other sites More sharing options...
Guest Alan H Posted May 14, 2007 Share Posted May 14, 2007 Hi I noticed the other day that my temperature gauge was climbing high and when I checked I noticed that the fan wasn't cutting in. I unplugged the fan connection from the thermo switch and bridged the connector and the fan whirled in to life...so no problems with the fan. I then assumed that it was the thermo switch so went to Fords and purchased a new one which I fitted yesterday but this has made no difference i.e. the car over heated and the fan never kicked in. I've now had to re-bridge the connector again but this means the fan is always on whilst driving (not a problem other than the noise). Is there anything else which can affect the temperature sensor or would you agree with me that the new thermo switch is perhaps faulty ? Any advice appreciated. Rgds Brett is it possible that the temp gauge has starting reading high and that the temperature is normal...you could try connecting the thermo switch to an ohm meter and then put the end of it in water and heat up.at around boiling point or above you should get a closed contact reading on the meter. the fan should cut in just below the red ..hope this helps Link to comment Share on other sites More sharing options...
Guest Brett Posted May 14, 2007 Share Posted May 14, 2007 Hi Alan Thanks for the suggestion...and I did myself wonder this initially but put the idea out of my mind when the needle went off the scale, but with the thermo switch continuously bridged the temperature stays at around 3/4. Today I took the new switch back to Ford's and told them it is faulty and that I wanted a new one which they have ordered me. If I get the same result with a second new switch then I will obviously have to start exploring other ideas. I have wondered whether it is possible to test the switch like a thermostat in boiling water and if I do have to explore other options then I might well dunk the old one in a pan of boiling water and see what happens. On the other hand, in the Haynes manual it says that "if bridging the thermo switch proves the fan works then the switch is faulty and should be replaced". Haynes doesnt offer alternatives e.g. thermostat jammed closed or open etc so I dont see what else it can be ! I will keep this post updated of progress - positive or negative Fingers crossed the second new switch does the business Rgds Brett Link to comment Share on other sites More sharing options...
Guest Brett Posted May 19, 2007 Share Posted May 19, 2007 Well I have a real mystery here and if anybody can solve this or give me some ideas I'd be extremely grateful ! ......the story goes as follows: My 1989 (G reg) MFi cabriolet is overheating with the needle going off the scale because the fan never switches on. I know the fan works because I have bridged the actual thermo switch connector, which connects to the thermo switch, and the fan whirrs in to life. So, last week I bought a new thermo switch but this made no difference. So this week I took the new switch back to Fords and told them that it might be faulty. They have sent this away to be tested and I had to buy a new one in the mean time ! Today, I fitted the second new thermo switch and reconected the thermo switch connector and the car over heated like before ! I know the the thermo switch connector is live because bridging it makes the fan spin. I checked the hoses (top and bottom of radiator) and both were red hot. Also I disconnected the top hose and cranked the car a few times to prove that the waterpump was working and it was...and also that I dont have an air lock or a jammed shut thermostat. I tried the original thermo-switch in a pan of boiling water but I couldnt get a reading across the pins. So, I wondered whether (because water under pressure has a higher boiling point) the water in a saucepan wasnt hot enough. My only conclusion is that the thermo switch has too high an operation temperature and this is why it isnt operating the fan thermostatically. I have had to re-bridge the fan connector and have the fan on all the time via the ignition which apart from the increased noise isnt a problem but this is truly making me scratch my head so if anybody can offer something else to check Cheers !!!! Brett Link to comment Share on other sites More sharing options...
Guest jaffa90 Posted May 20, 2007 Share Posted May 20, 2007 hello m8 i had the same prob with mine and it was one of the yellow relays in the fuse box. hope this helps. Link to comment Share on other sites More sharing options...
Guest Brett Posted May 20, 2007 Share Posted May 20, 2007 Sorry to sound like I doubt you mate, but what would this relay do ? I have power to the thermo switch and bridging this makes the fan work. Surely the fault is somewhere down by the thermo switch or am I missing something ? Cheers ! Brett Link to comment Share on other sites More sharing options...
Vincygav Posted May 20, 2007 Share Posted May 20, 2007 Possibly the relay needs a certain voltage from the fan switch tomake it work. Its worth a try changing the relay or checking the wiring. Link to comment Share on other sites More sharing options...
Guest Brett Posted May 20, 2007 Share Posted May 20, 2007 Please can some body clarify that a relay exists in the fan circuit because..... I have a continuous ignition live wire which goes to one of the pins of the thermo switch. LIVE -------> Pin 1 of THERMO SWITCH-------> pin 2 of THERMO SWITCH ------> FAN The other pin of the thermo switch wires directly to the fan motor. Consequently, if the thermo switch was working then this would feed a live through the thermo switch to the fan but this isnt happening i.e. the fan isnt switching on. But if I bridge the thermo switch, i.e. connect the LIVE straight the fan then it operates and this is how I drive the car at the moment with out it overheating. This is therefore made me think that it must be the thermo switch that is faulty because it's the only thing that stands in the way of a live going straight to the fan. However I have tried two brand new thermo switches and the fan still doesnt cut in and the car over heats. Now...here's my questions If a relay existed in this circuit (which I am scratching my head to believe) then 1) Where in this circuit would a relay take any part to play 2) If there is a relay in the circuit and how come the fan stays on continuously when I bridge the thermo switch. Personally I think the thermo switch has too high an operational temperature but surely two brand new switches (plus my original switch) wouldnt be faulty! Now......one other factor which I am thinking is that if the thermostat was jammed OPEN i.e. the water is continuously being circulated rather than being held back and therefore creating pressure then may be the temperature isnt getting hot enough to activate the thermo switch. However surely when the car is over heating and the temperature gauge is off the scale the switch should work.....so this kind of shoots my theory down in flames ! Help before I go mad ! Rgds Brett Cheers! Brett Link to comment Share on other sites More sharing options...
Guest sjc Posted May 21, 2007 Share Posted May 21, 2007 fuse 12 - Bk wire to switch......switch Bk/R wire to motor.......motor Bn wire to chassis.....cant see anything else in the circuit. switch is normally open when cool, closes when hot and fan motor runs. Unfortunately I cannot find anything in the spec about the temp the switch closes, but you are right in that if you remove the plug from the switch and short short it out, if the fan runs, the circuit is ok. That does point to the switch, which you have changed......so if the switch is okay its not getting hot enough, matbe there is no coolant flow around it. Link to comment Share on other sites More sharing options...
Guest rst_mk5 Posted May 21, 2007 Share Posted May 21, 2007 Have you checked the thermostat itself these can get stuck used to have a lot of probs with my rs turbo but now ive fitted a 82 degree stat and aint had a problem since Link to comment Share on other sites More sharing options...
Guest Brett Posted May 21, 2007 Share Posted May 21, 2007 Thanks SJC and RS_MK5 for the latest updates ! SJC I assume you must have a similar cabbie to mine (MK4 - MFi) given the knowledge of the wire colours etc. I think that the thermostat must be jammed open or has too high a temperature rating. My reasons for this: 1) When I removed the hose from the waterpump and cranked the car for a few seconds, water pumped out of the waterpump 2) I think that this would also confirm that the thermostat is not jammed closed ???? Running the car with the thermo switch bridged prevents the car from overheating, so consequently I believe the water must be circulating. The only thing baffling me now is that if I re-instate the thermo switch the temperature gauge goes off the scale eventually because the fan doesnt activate. The water temperature at this point must be screaming hot so why isnt the fan operating ? If fit a thermostat of e.g. 85degs then surely this is going to give me more problems Cheers ! Brett Link to comment Share on other sites More sharing options...
Guest rst_mk5 Posted May 21, 2007 Share Posted May 21, 2007 Thanks SJC and RS_MK5 for the latest updates ! SJC I assume you must have a similar cabbie to mine (MK4 - MFi) given the knowledge of the wire colours etc. I think that the thermostat must be jammed open or has too high a temperature rating. My reasons for this: 1) When I removed the hose from the waterpump and cranked the car for a few seconds, water pumped out of the waterpump 2) I think that this would also confirm that the thermostat is not jammed closed ???? Running the car with the thermo switch bridged prevents the car from overheating, so consequently I believe the water must be circulating. The only thing baffling me now is that if I re-instate the thermo switch the temperature gauge goes off the scale eventually because the fan doesnt activate. The water temperature at this point must be screaming hot so why isnt the fan operating ? If fit a thermostat of e.g. 85degs then surely this is going to give me more problems Cheers ! Brett Another thing to check are you gettin hot air inside the car you might have a blocked heater matrix or something ford are notorious for water problems.... and no it dont seem like it could be the thermostat but in my experience it normaly is.... bloody things lol Link to comment Share on other sites More sharing options...
Guest sjc Posted May 21, 2007 Share Posted May 21, 2007 I have got an 89 MFI but was reading the wiring diagram in the manual. You can test the stat in a pot of water though, it should start to open at 85-89C and be fully open at 102C. with the stat shut coolant goes to block, head, manifold and heater matrix, when stat opens the radiator as well.......I would guess that the fan switch comes in somewhere above/between 90 and 102C cos if theres no flow through the radiator its pointless having the fan running....that may explain why it was hard to test it in a pot of boiling water. RST Mk5 is diverting coolant to his radiator earlier to get slightly cooler running, maybe something you should consider. Gonna confuse meself now... I thought that the fan was extra help, under normal driving conditions ie forwards with air flowing through the radiator, the stat on its own should keep control of the coolant tempurature. When there is no air flow ie standing still the fan will kick in to help when the engine gets hot. Have you ever had your needles off to fit new dial faces? maybe its not as hot as you think. If its overheating under normal driving maybe you should have a go at sorting that. By no coolant flow, I meant in the immediate area of the switch...never had one off, could it be sitting in some gunk or in airlock or in coolant behind and airlock. Hope ive not confused it more, being a spark I would tend to trust that the circuit working and look elsewhere, good luck, mick Link to comment Share on other sites More sharing options...
Guest Brett Posted May 21, 2007 Share Posted May 21, 2007 Hi Mick You mentioned the dials and you have semi hit a nail on the head ! I've not had the car all that long and I noticed that the temperature needle never moved. When I checked the connector on the back of the dial was loose. Once I pushed this on properly the dial started working. When the car is initially started the temperature rises to half way and stays there with the thermo switch bridged (fan continuously on) or rises eventually off the dial if I connect the thermo switch which doesnt operate the fan. I assume that this has been happening for a while or atleast since I've had the car so I've been lucky the engine hasnt cooked, but the radiator has never boiled over ??? I'm not sure how much a thermostat & a gasket is going to cost me from Fords but I'm thinking it has got to be my next best angle of attack! I was only concerned that if the thermo switch isn't kicking in when the gauge is off the clock, (I suspect gauge is accurate as the fan hasnt operated at this stage), then putting in a new thermostat which is now going to close / restrict the water flow might cause MORE problems. As mentioned previously the water must be flowing i.e. thermostat jammed open because the car doesnt overheat with the fan continuously on. I can only hope that if the thermostat isnt closing, the pressure is standard pressure and so the water isnt getting to e.g. 105degs and therefore the thermoswitch isnt activating My sincerest thanks to you for taking the trouble to respond (and get the Haynes manual out !) Rgds Brett Link to comment Share on other sites More sharing options...
Guest sjc Posted May 21, 2007 Share Posted May 21, 2007 just a quickie, when I was a lad, we used to take the stats out of cortina's and have it flowing through the rad all the time, is there a reason why you cant give it a go....someone may be able to give a reason why not, until you can get another. Link to comment Share on other sites More sharing options...
Guest Brett Posted May 21, 2007 Share Posted May 21, 2007 Regarding the thermostat I have 3 possibilities 1) It isnt there ! 2) It's there but jammed open 3) It's there and working but the thermo switch isnt working (unlikely) as I have replace with 2 new ones When I disconnected the rubber hose off the water pump and cranked the engine over, the water pump pushed water out, which stopped when switched the engine off This hopefully proves the pump is working. If the thermostat was jammed closed then surely the car would over heat straight away and the radiator would never get hot which it is. Consequently taking the thermostat out as you suggested would give me what I think I have now. However I agree I too have heard it done on cars which over heat Rgds Brett Link to comment Share on other sites More sharing options...
Guest rst_mk5 Posted May 21, 2007 Share Posted May 21, 2007 Regarding the thermostat I have 3 possibilities 1) It isnt there ! 2) It's there but jammed open 3) It's there and working but the thermo switch isnt working (unlikely) as I have replace with 2 new ones When I disconnected the rubber hose off the water pump and cranked the engine over, the water pump pushed water out, which stopped when switched the engine off This hopefully proves the pump is working. If the thermostat was jammed closed then surely the car would over heat straight away and the radiator would never get hot which it is. Consequently taking the thermostat out as you suggested would give me what I think I have now. However I agree I too have heard it done on cars which over heat Rgds Brett The water in your engine will still flow with thermostat shut i belive it has 2 routes in the bottom of rad and out via top into stat also it goes round back of engine and through heater matrix and then back into system vis themostat houseing i still think you shoudl chage thermostat and try again its gonna csot you about £5 to see if its that or not instead of everyone keep geussing..... And as for taking thermostat out that will work but water will takes ages to heat up and can damage the engine due to this plus it will hit a certain temp and stay there wont go down again..... I have owned several fords over the years and with problem you have first thing i would have done was chage thermostat its a very common prob for a ford..... Link to comment Share on other sites More sharing options...
Guest ASHESCAB Posted May 22, 2007 Share Posted May 22, 2007 Hello mate! I have a very simular problem with my mk4 87? and i have changed thermostat, fan sensor and thermo switch? but still i have permenant fan and gauge reads that temp is 3/4 high? so im at a miss too? the gauge reads this even when not run and just with the ignition on? lol I hope you get is sorted mate! Link to comment Share on other sites More sharing options...
Guest Alan H Posted May 22, 2007 Share Posted May 22, 2007 Brett, 1) when you switch on with engine cold does the temp gauge stay at cold? 2) when its getting hot and no fan does it eject water from the system(a sign of over heating) 3)your method of testing the water pump is crap(sorry dont mean to be rude)best thing to do is remove it and check the condition of it visually..over time the impellor can corrode away,causing limited flow Link to comment Share on other sites More sharing options...
Guest Brett Posted May 22, 2007 Share Posted May 22, 2007 Well guys I am truly truly stumped on this one !!! Tonight I 1) Removed the thermostat housing 2) Flushed the whole system with a hosepipe until I had clean water coming out. 3) Whilst I bought a new thermostat today, I didnt fit ANY thermostat and replaced the housing 4) I then refilled the whole system (without anti freeze - want to get this sorted before I start wasting antifreeze !) To answer Alan's previous question the temperature needle always climbs immediately, at cold, to the middle of the gauge i.e. because it is a right hand gauge it climbs from 6oclock to 3 oclock. Well guess what..... With the engine running the temperature gauge slowly (over ten mins or more) climbed up to the red (approx 1 oclock) and I reckon if I left it it would have climbed off the scale. During this time the fan never kicked in once !!!!!!!!!!! I am confident that the water is circulating because the radiator gets hot and so do both top and bottom hoses Incidentally, When I had the thermostat housing off the car you could see the end of brand new thermo switch inside the thermostat housing and it was clear and clean. Now my ONLY suggestion is that the thermoswitch is calibrated too high to activate the fan but if this was true then why would I have had this problem with 3 thermo-switches (Original one and two brand new ones from Fords) I honestly dont know what else to try....so any ideas are welcomed ! Cheers! Brett Link to comment Share on other sites More sharing options...
Guest Brett Posted May 22, 2007 Share Posted May 22, 2007 Alan I've been having a think about your line of thought about the temperature gauge at cold.... With the ignition totally off, the needle sits at approximately 6-5 oclock (below the minimum) and then when the ignition is switched on the needle rises to 3oclock and then red is at approx one oclock. (my gauge is vertical - facing right) However, I've not had the car all that long and the other day I noticed that the temperature needle never moved. When I checked the connector on the back of the dial I noticed it was loose. Once I pushed this on properly the needle started moving and it was then that I noticed it starting to go into the red. BUT.....I had not had any issue with the car boiling over / overheating it was merely the fact that the needle was always going into the red and the fan was never cutting in. Since I've had the needle moving again I have always switching the car off once the needle gets to the red or drive the car with the connector bridged and the fan always on. If the needle is showing INCORRECT and I left the engine running the needle will rise off the clock beyond the red....and maybe the fan will eventually kick in - I've always stopped the car at red. If the need is CORRECT the fan wont ever kick in and I am going to damage the engine letting the needle go beyond the red. Is there anyway I can prove the accuracy of the needle ? What would happen first with if the needle is correct and I allow the needle to go beyond the red ? Will I be able to determine that the engine is overheating e.g. blow out into the reservoir etc ? I've never witnessed this so I am unsure as to what to expect but dont want to do any damage Cheers ! Brett Link to comment Share on other sites More sharing options...
Guest rst_mk5 Posted May 22, 2007 Share Posted May 22, 2007 Just read this again and i had same sort of problem with my rs turbo lump i put the wrong temp sender in head and it kept saying the temp was off the scale the maybe you have the wrong temp sendr switch from front of head next to thermostat housing..... before you made it sound like you had actually overheated or maybe i just read it wrong..... Turned out id fitted temp sender for a cosworth engine fitted correct sender and its been fine ever since Link to comment Share on other sites More sharing options...
Guest sjc Posted May 23, 2007 Share Posted May 23, 2007 turning into a saga lol Brett I mentioned about the accuracy of the indicator earlier cos (as alan said about expansion) it doesnt sound like the coolants getting hot enough to close the switch. And it shouldnt go straight to the middle when you start it of a morning, you may be getting a false reading from the temperature sender or the dial itself may be knackered. got the drawings out again, theres a transistor in the clock unit itself, this powers both the temperature sender and fuel level senders via the guages, ie guages first. The temp one is the red/white wire straight to the sender (heat variable resistor) itself, which is earthed at the chasis. Now the guessing bit as my car is 40 miles away at the mo so I cant check. I would imagine the sender has very high resitance when cold so no current flows to the chasis and needle doesnt move, as coolant heats the resistance decreases, current begins to flow and needle works its way up.......unfortunately it could also work the other way (no resistance when cold) depending on how the coil behind the needle was designed...hopefully someone will know or be able to check. You could always start your car from cold and reset the needle to see where it goes??? Link to comment Share on other sites More sharing options...
Guest Brett Posted May 23, 2007 Share Posted May 23, 2007 Its better than Eastenders this saga LOL ! As mentioned, because the temp gauge wasnt working and the car wasnt physically overheating I never knew of any problem. My troubles only started happening when I got the clock working again and the needle has been going into the red and I saw this as an overheating car. Given what I have changed (thermostat switches) and the comparable difference to the start position of my temperature gauge at 3 oclock and other people's at 6:00 oclock I think that may be the car hasnt physically been over heating at all ! Since I got the gauge working (albeit correctly or incorrectly) I have always stopped the engine when the needle has been getting to the red for fear of doing any damage. I do have a spare set of dials and I am going to fit these and see if I can get either the correct action of the temperature guage or atleast something different to what I have now. There are currently no needles on my spare dials and this might sound like a daft question but I have to ask it.... Is the initial setting of the needles merely, turn the ignition off and fit needles to a guessed lowest position or is there a minimum place that the needle will go down ? I have a feeling that the needles will spin round and round the clock so there is no minimum position you have to just guess where it is.... I REALLY REALLY appreciate the trouble some of you guys have taken to advise me...it's what makes this web site such a great team spirited place to frequent. I think the end is in sight ! Rgds Brett Link to comment Share on other sites More sharing options...
Guest sjc Posted May 23, 2007 Share Posted May 23, 2007 Since I got the gauge working (albeit correctly or incorrectly) I have always stopped the engine when the needle has been getting to the red for fear of doing any damage. Brett lets hope it works, hope there was not too much sitting at the roadside with the bonnet up lol oh by the way, Ive got 2 sets of mfi clocks but the needles are not swappable, one has just a wire/pin for the needle to push onto, the other the needles puch onto plastic pegs.............hopefully your spare is the same as the one youve got fitted Link to comment Share on other sites More sharing options...
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