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The compressor works the engine harder at idle. More power=more heat rejection=more cooling required. You didn't think it was free did you?
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But it doesn't seem to be right. If its a hot day, I can get into the car for the first time (so the engne is cold), turn on the AC and the High/Low speed fans will start cycling on/off straight away. There would be no need for that amount of engine cooling straight away.
Also, when this happens, the AC isn't working like it should do as I only get the cool air during the on cycle. As I understand, there should be no cycling of the two fans, only the low speed fan should be constantly on when AC is on (in my experience with other cars I've had, that is usually enough to keep the engine cool at idle during a hot day)
Edited by Scottishrob79 on 12/07/2011 at 18:32
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Rob-sorry, you're right. Shouldn't be any cooling fan on from a cold start. Perhaps there's a short in a temperature sensor-which corrosponds to a very high temperature.
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The strange thing is though, if it was a faulty sensor, wouldn't the fans cycle regardless of whether the AC is on or off. When the AC is off, no fans run.
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The fans are cycling on/off, low speed fan should be staying constantly on when AC is on
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With the a/c switched on ,both fans should start up on slow speed a few seconds before the a/c compressor is engaged.These stay on slow speed up to a road speed of 60kph.Fast speed on both fans should only come on under high engine temp or high a/c pressure/load.Some focus models have an additional under bonnet temp sensor attached to the battery bracket to bring on fans when engine bay temp becomes excessive.Also don't forget that the a/c is engaged automatically when defrost is selected on the heater panel.Is it possible that the a/c system has been overfilled with gas?this will cause the fans to cycle erratically.hth
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I have had the condenser replaced recently, so the system was filled, and then I had the AC man out again to check the pressure recently when I asked him about the fans and he said it was all fine. Do you think one of these temp sensors could be faulty? As I said, it happens in warm weather (20c+), even if I haven't used the car
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I think you're got too much gas in the a/c. The pressure is rising and kicking on the high speed fan. The a/c guy should be able to see if the pressure is rising above the low speed threshold, kicking in the fan, then reducing the pressure, and so on.
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He's already tested for that and everything was fine. Also, it did it today (only 17c) and that was turning the AC on for the first time today, after previously using the the car a couple of hours before. The funny thing is, when I realised this, I turn the AC off, turned up the fans fully and turned the AC back on and the low speed fan kicked in normally
Edited by Scottishrob79 on 13/07/2011 at 16:53
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I wanted to bring this back again because I am still having this strange fan issue. Could it be a faulty sensor or switch that is doing this??
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Anybody??? I'm thinking about changing the High Pressure switch (the one under the drivers wing) Can it be changed without losing any gas?
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To be perfectly honest,Focus models of this age give very little trouble on the a/con system.Apart from the odd pipe or condenser rad renewal,I have never had any problems with any sensor or pressure switch.(btw, these can be changed without a degas,as there is a valve behind them).As previously suggested by myself and others,you need to get the gas charge quantity re-checked.It should be approx 750 gms.If possible take the car to a different a/c specialist to verify the amount.Also (if poss)can you post the hi and low side gas pressures with engine running.hth
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Hi, thanks for the reply. The thing is, after searching different forums, I've seen a couple of other people have had the same problem and the answers seem to point at a faulty pressure switch because if it was high pressure in the system, the fans wouldn't come on as quickly as 10 secs after starting the A/C, like mine do. Any truth in this?
As I've said previously, it doesn't happen all the time. If it was high pressure, wouldn't I get the cycling fans on every time I use it? Take today for example, I turned on the air con three or four times and I was getting the cycling fans every time. Got home, then had to go out a couple of hours later, and I got the normal low speed fan operation.
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Just an up date on the above problem. I bought a high pressure switch last week from ford and now everything is ok
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I want to bring my old thread up as I am still having problems with my fans cycling whilst the a/c is on. It is now cooler, but I still turn the a/c on for a few minutes every few days. Still noticing sometimes when running the low speed fan runs as it should, and other times its fast cycling on/off with the high speed fan.
To recap, I have had the pressure tested twice by two people (both times fine), I have replaced both low and high speed relays. I have replaced the high pressure switch and checked all fuses. I have been told it won't be the fan resistor because if it was, I would be getting the cycling fans every time I use the a/c. The compressor is running fine and when the fans are running I'm getting cool air.
Had thoughts that it could be a faulty coolant temp sensor, but I only get the cycling fans when the a/c is on and the temp seems perfectly normal
Please help!!!!
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Also, just to add, I did the self diagnostic test the other day (where it resets the climate control flaps and gives fault codes), no fault codes came up
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As predicted,I did not think a new pressure switch would fix the problem.For the fans to only cut in on high speed with the a/c on tends to suggest that there is abnormally high pressure in the system.Is it possible that the condensor that was fitted is of inadequate quality to remove excess heat/pressure ,Or is there a slight blockage in the system,possible fault in the orifice tube restrictor valve??Just a few thoughts.hth
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The second bloke who checked the pressure checked the condenser and said it was a very good quality one. As I said previously, there will be some days when I use the car the a/c will work perfectly the whole time I am using is, then there will be other times I will have the fan issue the whole time the car is running
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The other thought is if its due to a blockage or excess heat/pressure, why would the low speed fan not come on at all on the days I'm having trouble. Wouldn't the low speed fan come on, then the cycling starts once the ECU realises there is a build up of heat/pressure
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Hi again e&a/c doc, I'm going to have a look at the orifice tube you mentioned. Could you tell me where abouts it is? If nesessary, where I would get a new one and could I fit it myself?
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Right, today I had a new accumilator and replaced the orifice tube, then a regass. When the air con man went, I started the car and a/c, FANS CYCLING STILL!
Anyone got any other ideas????
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My idea: Rip out the AC system and bin it. Was sorely tempted to do same with my old Focus after paying £70 for a regas and several weeks later the refrigerant had gone east and my fans were cycling on and off with no cold air coming out of the vents!
With the Ford heated screen for winter, I'd have been happy to get rid of the AC and lose some weight / clear some clutter from the underbonnet area.
You might even be able to flog off some of the parts to cover your losses!
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Unfortuately for me, a/c is a must, thats why I'm so determined to get it fixed.
Replaced the cylinder head temp sensor the other day, just incase it was giving a false signal to the ecu when I turn on the a/c, but it still hasn't solved the problem. So far I have replaced/checked;
Condensor (old one was leaking)
Resistor
Low and High speed relays
High pressure Sensor
Accummulator
Orifice tube
Regass and checked pressure twice (with two different engineers)
No fault codes coming up on self diagnosis test
Any other help would be appreciated
Edited by Scottishrob79 on 27/01/2012 at 11:26
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I am a little concerned that you are throwing parts and time at this car for no good reason.The only item that I can see that needed replacement was the condensor,not unusual as this is the most common failing on Focus models (and most other cars).So,just to recap,if the condensor fans are cycling into high speed mode only when the a/c is engaged,the the a/c system must be seeing a high pressure situation.If you are happy that the gas fill quantity is correct,then it is possible that the new condensor has a fault and is not allowing the temp/pressure of the gas to dissipate.It would be nice to know what the hi pressure reading is indicating when the fault occurs,but obviously would need the gauges attached on start up.Please don;t spend any more on this until we can see those readings.hth
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The thing is, this problem is so random, I can literally start the car and then the a/c and there will be no fans until both fans start high speed cycling a minute or two later. I can then stop the car and then start it (and the a/c) again straight away and the low speed fan will kick in as normal.
If it is a condensor problem, how can turning the car off and then on again sometimes rectify the problem?
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One thing I have noticed about the bloke who fitted the condenser and the accumulator, was when he finished both jobs and refilled the system, the refill seemed to take all of 10 minutes. As I understand, the system should be deep vacuumed for leaks and taking out moisture and air and that should take at least an hour.
Could my problems stem from this? (An airlock maybe)
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