Many thanks guys, I knew I could rely on you!
Regards.
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If the connector and resistor contacts have burnt out /overheated ,then a revised resistor and connector with fly leads will need to be fitted. Ford part #1226034 .About £65.
Hi,
Been to the Ford parts dept, they dont stock it though 1226034 seems to be revised cabling without a resistor, I would still need the 6878445 resistor at £25 = vat on top, total £108.26 with the VAT.
So what is the benefit of the revised cabling?, why not crimp on spade connectors?
Many thanks.
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the part # I quoted is a "kit" that includes a revised resistor with a flylead moulded/attached to it and an adaptor harness and plug that can be crimped or preferably soldered to the existing wiring.. Nothing else is required apart from some manual dexterity.!! I have fitted loads of these (mainly to diesel models)
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"Includes a revised resistor", grrrrreat, many thanks.
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100w 1 ohm resistors (metal cased, mount on to a heat conduction surface) cost about £5 from RS. Can't somebody supply info on the value? Other values are available.
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pmh (was peter)
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Thanks pmh however this part is more than just a resistor, it is mounted onto a backplate that fits within the rad shroud and comprises a coil as well as a resistor, the new part may well be different though is clearly designed to solve issues with the old part as well as integrate with the existing wiring.
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Interesting! can you be more specific about the coil??? I can imagine that a thermostat could be integrated into this module (and possibly a relay) but what else could it be. If it is a series resistor that fails there is no reason why this could not be replaced on its own.
elekie may have the answer or anybody with a circuit diagram..
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pmh (was peter)
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Hello,
Re high speed cooling fan cycling on and off when aircon / climate is on.
Any further thoughts on this, as mentioned I had a reoccurrence of the cycling fan issue early in the summer, during the peak summer - due to high ambient temps - the high speed fan was on all of the time whenever the aircon / climate was switched on and all worked fine. I changed the resistor for the newer type (Ford part #1226034) a couple of weeks ago using a connector block to wire it into the loom, a straight forward job. All seemed well, however today - lower ambient temp - I noticed the high speed fan cycling on and off again. Could there be any other cause? I guess I should check my connections.
Many thanks.
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Glad you got the resistor sorted.I would recheck the wiring especially the connector block you have used- there is a lot of current being passed here.Also check that both fans are running,could be one is open circuit causing the other to run full speed.hth
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Many thanks, I thought I had it sorted though symptoms during cooler weather (cycling fan) are the same as before. Both fans were running after I fitted the revised resistor, I will check the fans and wiring tomorrow and go from there. Will post back here.
Best regards.
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OK, my wiring to the resistor seems fine.
It is difficult to replicate previous circumstances due to variations in engine temp, ambient temp, car interior temp etc however where as yesterday it seemed that the high speed fan circuit was cycling high / low every few seconds, today it seems that the compressor is cycling on and off with the fans running at high speed constantly, that is despite the engine temp being low (so no cooling required), the ambient temp being around 18 deg C (not very hot) and the interior temp set to 22 deg C (so perhaps just a little cooling required). I have swopped around the two fan relays in the aux fuse box to no avail. I am lead to believe that the high speed fan circuit should only operate at fairly high ambient temps to assist the condenser unless triggered by the coolant temp sensor via the ECU.
Ice cool air is available if required so low gas pressure seems unlikely however it is clear that the compressor may cycle if gas pressure is low. Though equally it may cycle - I assume - if it has little work to do, i.e. not much cooling required exagerated by the fans working overtime?
So I am assuming that the problem is the high speed fan circuit running constantly and / or cycling and not low gas pressure, though I am open to suggestions either way.
Many thanks.
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I am not particularly knowledgable on these cars, but I will try to provide some info.
IIRC the a/c is essentially contolled by the engine ECU. It has three output - one which drive a relay to operate the compressor clutch; one o/p to operate the low speed fan relay (via that resistor) and another relay to operate the high speed fan relay (which essentially is a 12V feed bypassing the resistor).
The inputs to the control are the engine temp sensor and pressure sensors (dual pressure switch).
It sounds like the ECU thinks the blowers need to run at full speed, this could be because of:
1. Incorrect signal from CTS (thinks engine is too hot).
2. Signal from pressure switch (thinks pressure is high).
If you have switch the relays over then you know they are OK.
It may be that you will need to have the engine ECU scanned for fault codes - could be a dodgy CTS, or connection to it..
In terms of the a/c control itself, it has a self-diagnostic function that you can access by holding in the footwell button when turning the key on - plus doing some other things. Can't remember at the moment, but I may be able to find details if you need them.
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Thanks Aprilia.
The inputs to the control are the engine temp sensor and pressure sensors (dual pressure switch).
>>It sounds like the ECU thinks the blowers need to run at full speed, this could be because of: 1. Incorrect signal from CTS (thinks engine is too hot).
I have thought of that however the fans cut ot when the aircon / climate is switched off where as if the engine were hot, or rather the ECU thought the engine were hot, the fans would run all of the time?
2. Signal from pressure switch (thinks pressure is high).>>
Do you mean a faulty high pressure switch? There are seperate low ang high pressure switches hence my thought that low gas pressure could cause the compressor to cycle?
In terms of the a/c control itself, it has a self-diagnostic function that you can access by holding in the footwell button when turning the key on .......... I may be able to find details if you need them.
Could be useful, many thanks.
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Yes, if the fans are not running when the a/c is off then that suggest that the CTS is OK.
There are actually two switch units on this car. As I understand it (I'm NOT an expert on Mondeos) one of the switches is a low refrigerant switch and deactivates the compressor if there is insufficient gas. This one is under the OS wheel liner on the LP pipe.
There is another switch in the engine compartment - this is a dual pressure switch (high and low-pressure switches built into one unit) on the HP pipe from the condensor to the orifice. I think it is the operation of the LP switch here that controls the compressor cycling - but you would really need someone more knowledgable than me to confirm this though.
I will try to locate the self-diagnosis info - yours is an auto-climate control model I assume? (no self-diag on manual air con cars).
It does sound like your problem is more involved than just the resistor having failed again.
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I will try to locate the self-diagnosis info - yours is an auto-climate control model I assume?
Yes, thanks Aprilia.
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the self diagnosis mode of the climate control only relates to functions of the cabin unit .I do not think this will help.It is also used to show software version and to calibrate the hot/cold air blend flap.One point that I would like to confirm,Is the radiator (coolant )getting hot.?It is possible that the fans are cycling full speed because of a coolant flow problem.
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Yes, I agree self-diag will probably not help, I was clutching at straws. Sounds like its really tied up with CTS signal and the pressure switches. I wonder if the a/c pressure could be going too high (because of a blockage) and tripping the HP switch which would turn comp off? Keep saying I'm no expert - but I think high fan speeds on most cars are initiated by CTS signal (i.e. hot coolant) rather than anything linked to the a/c.
Do the cooling fans work normally with the a/c off?
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Hi All,
I am confident that the cooling system is fine, as per above comment regarding the CTS if it were cooling related surely the fans would continue to run when the a/c is off.
Aprilia says of the fan control "one o/p to operate the low speed fan relay (via that resistor) and another relay to operate the high speed fan relay (which essentially is a 12V feed bypassing the resistor)." In this scenario I guess that as the resistor (perhaps thermistor is the correct term?) heats up the resitance increases thus cutting the low speed fan current however iof so what sensor's info does the ECU use to switch the high speed fan relay?
Could it be the other way around?, i.e. the low speed fans run by default swiched by the relay when a/c is turned on then as the resistor heats up the resitance drops thus allowing current to the high speed relay?
If so a short in the resistor circuit would perhaps enable the fans to run constantly?
It seems from research I have done that cycling of the compressor is normal, would you agree or does this indicate low or high pressure?
If so the problem is simply the high speed fans being on when not required or sometimes cycling on and off, otherwise everything works fine, cooling and aircon wise.
Once again many thanks to all.
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To clarify..
There are two seperate outputs from the ECU - high-speed and low-speed. Each goes to a relay.
When the low-speed relay is switched, it supplies 12V to the fans via a resistor which drops it to a lower voltage and so the fans run at low speed.
When the high speed relay is switch it supplies 12V directly to the fans (bypassing the resistor) - so they run at full (maximum) speed.
If the resistor went short-circuit then the fans would run at high speed when they were being 'commanded' to run at low speed. If you pulled the low-speed relay then the fans would stop.
If the resistor went open-circuit then the fans wouldn't run at low speed - they would be stationary, but would run when high speed is commanded.
Now, as said before, I'm not much of an expert on this system, but based on my experience with other systems I would hazard a guess at the following - with a/c on the fans should run at low speed. With a/c on and coolant hot the fans should run at high speed.
The compressor would be controlled by the pressure switches, the a/c controller (i.e. internal set temp and internal temp sensor) and a WOT 'relief' (i.e. compressor switches off at full throttle). Under light cooling it would cycle. Often the idle speed controller will kick the idle up a bit to handle the extra load of the compressor.
The above is a bit of a guess though - ideally you need a manual for it and/or take it to someone who is familiar with the system. They are common enough so someone must know it chapter-and-verse.
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Thanks again Aprilia,
I thought that the resistor had some temp control function (hence my suggestion that it is a thermistor) because of its location in the rad shroud.
So if I remove the high speed relay from the fusebox and turn on the a/c the fans should run at low speed only ,if that is the case then the resistor must be OK. If the low speed fans dont run I could short the resistor circuit and the fans should run at high speed even without the high speed relay because the resistor is removed from the low speed circuit. If the fans then do run at high speed it would indicate that the low speed relay is ok and is receiving a command from the ECU so the resistor must be faulty.
This should definately tell whether the resistor is the issue, if it is Ok I can then look at the pressure switches etc.
I will try this this AM.
Best regards.
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Hello All,
Thanks in advance for any further considerations.
I have tried pulling the two relays one at a time however I am not sure which is which because there are two possible scenarios, they are numbered R7 and R9. When I pull R7 only no fans run, when pull R9 only the fans run at high speed.
Scenario 1/ R9 is the low speed relay however when I pull it and leave R7 (high speed) the fans run at high speed perhaps because the ECU is compensating for lack of low speed fans. When I pull R7 (high speed) and leave R9 (low speed) in place no fans run, the resistor must be open circuit so the fans do not run at low speed.
Scenario 2/ R9 is the high speed relay when I pull it and leave R7 (low speed) in place the fans run at high speed because the resistor is short circuit. When I pull R7 (low speed) and leave R9 (high speed) in place the fans do not run at all because the ECU is not demanding high speed fans.
Either way it is pointing to the resistor again though it would be good to know which relay is which.
Many thanks.
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I have found a wiring diagram for a 2003 model.
The low-speed relay is switched via a wire from the ECU which is black/blue
The high speed relay is switched by a wire which is black/white
Maybe this will help.
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IMHO resistors usually burn out, i.e. become open circuit. I would have thought that the resistor value you would be looking at here (if you had a meter) would be 0.5 to 1.0 ohm.
Good luck!
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I have attempted to measure the resistance across the resistor though it appears to be a short circuit so I have taken the resistor out of the circuit so now it is open circuit and the high speed fan cycles as before, back to square one! The high speed fan cycling on and off is clearly driven by the ECU compensating for the lack of low speed fans.
It seems that my original resistor went open circuit hence the high speed fan cycling, the replacement fitted a year ago did the same though the newer type fitted last month has gone short circuit. Strange!
Any thoughts?
Thanks.
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I have measured the resistance on the old resistor and it also appears to be short circuit, I wonder if I was right earlier and the resistance changes with temperature, this does not help answer why the fans run fast not slow though.
All reconnected, all working fine but for the pesky fans running at high speed as soon as the a/c is swithched on!
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The value of the resistance will be very small (a fraction of an ohm) - are you sure that your meter is sufficiently sensitive to discriminate between this small value and a direct short circuit?
If the resistor were short circuit then the fan would run at high speed only (the resistor is in the circuit to drop the voltage and give the lower speed when the low speed relay is activated). I don't think it will have any temperature measuring function.
The ECU has no means of sensing whether the resistor is defective or not.
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Thanks again!
are you sure that your meter is sufficiently sensitive to discriminate between this small value and a direct short circuit?
>>
Perhaps not.
If the resistor were short circuit then the fan would run at high speed only
Which is what is happening unlessthe resistor is disconnected.
I don't think it will have anytemperature measuring function.
>>
Are you sure? Why is it in the rad shroud then, perhaps only to keep cool? Also it has a coil alongside the resistor so I thought it might be a thermistor.
The ECU has no means of sensing whether the resistor is defective or not.
Not directly I guess though it knows to cycle the high speed fan circuit if the resistor is defunct or disconnected or the low speed relay is removed.
Best regards.
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If the fans are cycling high speed when the a/c is on, then it's seeing an excessive pressure, probably because the low speed fans aren't working.
They work low speed all the time the a/c is on. High speed if a/c pressure gets excessive, High speed if water temp excessive. If water temp continues to rise the a/c compressor will cut out.
So if you've got no low speed fan, then there's a problem with that circuit, usually the resistor or motor has burnt out or power is lost.
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Thanks Dave, the motors are fine, the same fans run either slow or fast - though mine only run fast - also its not a loss of current because the fans run fast even when the high speed relay is removed so only the low speed circuit has power. Must be the resistor me thinks though that is new.
I would like to test the resistor though i dont think my multimeter in precise enough.
Regards.
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The fan speed resistor is made up of 2 components.The heavy thick gauge wire is the resistive part (approx o.9 ohms) .The other small component mounted on the plastic is a thermal circuit breaker (fusible link).Also just a thought,has the system ever been recharged,perhaps it has been overfilled. btw the a/c systems on these mondeos are pretty reliable ,very few electrical probs other than the resistor or the fan(s) and a few flexible hoses.
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Cheddar
With the fans running you should be able to measure a voltage drop across the resistor. Put your voltmeter across the resistor's terminals and you should be able to measure a few volts drop (i.e. from Ohm's Law, V=I.R), where V is the voltage drop, I is the fan current and R is the resistance (0.9ohm). Lets say the fan current is around 5A then Ohm's law gives a voltage drop (measure across the resistor) of 4.5V. If the battery voltage is around 13.5V then this means the fans are running at about 9V (as an example).
If you measure NO voltage drop across the resistor and the fans are running at the full 13.5V (as seems to be the case) then this does indeed mean that the resistor has gone short circuit. It is unusual for resistors to fail in this way - they usually go high-resistance or open-circuit. Maybe connector(s) have failed and resistor is being shorted out in some way??
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Maybe connector(s) have failed and resistor is being shorted out in some way??
Thanks Aprilia, the connectors are all fine, checked today, I will try to measure voltage drop tomorrow and report back.
Thanks all for your continued considerations.
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has the system ever been recharged,perhaps it has been overfilled. >>
Hi, When I first noticed the fan cycling I had an aircon service at the Ford dealer, £60 IIRC, this was about March last year, this included a recharge, the dealer noticed that the multiplug on the resistor was burnt out and fitted spade connectors of there own back FOC, this did not solve the cycling so I replaced the resistor myself, problem solved until a repeat of the symptoms this summer.
So yes it has been recharged 18 months ago though has been fine for 15 months of that period.
Regards.
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Just thinking:
- When the high speed relay is removed the fans run at high speed, this must be via the low speed circuit and the resistor is not dropping the voltage (I will check the voltage today).
- When the low speed relay is removed the fans do not run at all, perhaps the ECU is not demanding high speed fans due to ambient or engine temp however if the pressure in the system rises one would expect the high speed fans to kick in, the fact that they do not indicates that the low speed relay also plays a part in the high speed circuit.
- When the resistor is removed from the circuit i.e. the low speed circuit is open circuit, the ECU is still able to cycle the fans at high speed presumably because it detects a rise in pressure, this again indicates that the low speed relay plays a part in the high speed circuit other wise this would also happen when the low speed relay is removed.
My assumption therefore is that the relays are in series, the high speed relay simply cutting the resistor out of the fan circuit, the low speed relay is required for the fans to run at all. This is supported by Aprilia?s earlier assertion.
I might have gone around in circles to get here though it seems to indicate that it must be the resistor that is at fault.
Regards.
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According to the circuit diagram I have (2003 TDCI with auto climate control) the two relays are in parallel. One feeding the motors directly (high speed) and the other via the dropper resistor (low speed). If the resistor was short-circuit then 'low speed' operation would actually be at high speed.
Can't account for why the fans don't run at all with the low speed relay removed.
Check out the resistor voltage drop - if the resistor is shorted then you've found the problem. If not, then you'll have to dig deeper into the problem!
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Many thanks again.
All seems OK today!
I know, I know, I must have inadvertently sorted it when disconnecting and reconnecting the resistor or removing and replacing the relays! Perhaps it was finger trouble fitting the new resistor though I had double checked the connections. I say "seems OK", it is just that there are so many variables when you account for ambient temp, engine temp, interior temp etc. I will see how it goes.
Neverthless I have measures the voltage across the connector block that is linked directly to the resistor when the fans are running and it show 5.2v against the battery static at 12.5v and at idle 14v.
This is a voltage drop of around 7.3v so perhaps the fan current is nearer 8 amps and the resistance 0.9ohm.
Re the relays I too have a wiring diagram in the Haynes manual, it seems that you are right that they are in parallel. As to why the fans don't run at all with the low speed relay removed, I guess the ECU will "think" it is running the low speed fans and simply cut the compressor if the pressure gets too high, perhaps it will only run the high speed fans at the behest of the CTS, at high ambient temps or if the difference between set (required) and actual interior temp is great thus demanding max cooling.
Thanks again to all, fingers crossed all is well, I will post here to update.
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