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Discussion Starter #1
Hey folks,

It seems to me that i manage to get my AC Compressor running. The previous owner had meddled with this unit and placed some sort things in between the clutch signal wire which i corrected it. Now the compressor works but the fans don't come live.

I have all new pressure switches for the single & the tri. Can you guys tell me what to do here.

Thanks.
 

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Discussion Starter #2
Ok,

did some more looking around and found one fan doesn't work when given power directly. But if i swap the connectors and gave power to it and it worked.

I traced it to the fuse box in the engine and the wires running to and from (black/brown) the fuse box are fine and conducts electricity. Now i'm at a loss why this is happening.

My theory is this. The fans work in series for low speed and parallel for high. Something is not allowing them to complete the circuit for low speed i.e for series mode.

If someone can tell me about this it's really great.
 

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Discussion Starter #3
Ok, went even further,

and got the fans working. It;s the single pressure switch not getting closed circuit. This was mentioned on several threads in this forum. So will be going to take a look at the pressures on the lines later on. Now re-assembling the system. Finally some piece with the system.
 

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This has been brought up before, and the P38 is notorious for it. The fans are nicknamed "the ghost fans". They hardly ever come on. I have witnessed mine turn on only twice this summer, and it only happens when the vehicle's coolant temp hits 210F. Otherwise they stay off. Unless it is overheating, it might not be worth the hassle, you might drive yourself mad trying to get them to work on a regular basis.
 

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I was reliably informed by a US marine mechanic that the fans very rarely come on at all and the only time they probolay would if I was in an extremely hot country and the pressure switch was activated.
In England where I am they would probolay never come on but he sent me some details of how to check if they would run by just wiring them live to the battery and they both worked ok.
 

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I have been down the same road searching for the problem with no running fans.
I did post a long time ago in another discussion about the same topic how they work.
But simply they operation of those fans have nothing to do with the temperature, they are depending on the pressure switch for the air-conditioning system.
Here in Sweden those fans have been operated only once for me in 3 years(!).
I have had in mind to put in a separate switch or even a temperature controlled switch in parallel with the pressure switch to be able to utilize those fans better, but so far I have not done anything yet.


Regards,
 

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Discussion Starter #7
Wow,

That's a lot of relief to know about this. Cos my AC technician told me that the fans should come up in 5-10 secs of engine start. (he's does japanese vehicle and not a LR tec tho).

In the mean time, i have currently bridged the two YB wires that goes to the pressure switch 2. I'll be running like this till i get a new water temp sensor as the idiots who have dismantled my dashboard have broke this and was hanging. So need to buy a new one.

Thanks all for your help here.
 

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In the mean time, i have currently bridged the two YB wires that goes to the pressure switch 2. I'll be running like this till i get a new water temp sensor as the idiots who have dismantled my dashboard have broke this and was hanging. So need to buy a new one.
My mechanic also wanted to fix my a/c fans. I told him that on this particular vehicle, they never come on. He looked at me strange and said, "no that is not possible". I looked back at him and said, "its a Range Rover, anything is possible" lol. He is right though, on every other vehicle I have ever seen, even the classic RR, discovery, etc. they all kick on and then kick off as the a/c cycles. If you are worried about the engine overheating and want to monitor the temps, get an obd scanner and plug it into the obd port. Make sure it can read real time data though. The temps should be from 190 to 210F.
 

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Discussion Starter #9
Thanks for the info mate.

I Think the engine cooling fan is so strong that it does the job of cooling the a/c radiator too.

I have got a HawkEye with me and its a neat little thing. For the P38 it can only get into the Engince ECU, ABS ECU and the AirSus ECU. I wish it had some more covered as i bought it to rectify the AC issue.

Will look into this much furthuer. And oh, the preivous owner had meddled with the system and done something as following:


[Earth]------[compressor clutch]-------[mechanical thermostat]-----[tri pressure switch]---


I have no idea why he/mechanic done this kind of a modification as it's really pointless. This thermostat only delayed the engagement of the clutch. He'd cut the WLG wire that goes to clutch and put this in the middle. I removed it, rejoined the wires and supplied the clutch directly with 12v, and presto it started working normally again.


Here's image of the thermostat.
 

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Hi guys my first post since being roverless around 4 months back :(. I struggled a lot with this issue with my cars. My first Autobio fans wouldn't come on and the thing for no reason at all would randomly overheat ! I had never heard or saw the fans working.

But once I changed the fuse box I heard them working a few times and let me tell you its loud. On my third and bestest 38 yet same thing but no over heating even though rad was corroded and clutch fan was limp 8) would only start to crawl into the red zone if left standing or crawling in traffic for a loooooong time and even then would not cross over into the red and stay with in the end of the normal range.

Just jumper the three fan relays to see if they are working and the wiring from the box til the fan is correct. This will work even with the engine off. One for series and one for full on for each of the fans.

On all my rovers though I took out the dual pressure switch under the left headlight. Totally unplugging it from the A/C bottle ( dryer ?? ) and jumped the switch ( Black and blue wire I thinks its been more than a year since I did this last so cant be really sure). So everytime I switched on the AC and the compressor kicked in the ground circuit would complete and the fans would come on in series. This was basically to get extra ice cold air from the A/C as it gets pretty hot here and stays that way !

People here have put in switches to manually turn on the fans from the inside if you do a search.

Cheers guy. Hoping to get a P38 one day again soon. Due to the crisis there have been some really nice ones being sold aswell as dirt cheap, but still not in the position to get a 2nd car :(

Until then I will be lurking around here. Still learning and maybe give back something from my Range rover days
 

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Totally unplugging it from the A/C bottle ( dryer ?? ) and jumped the switch ( Black and blue wire I thinks its been more than a year since I did this last so cant be really sure). So everytime I switched on the AC and the compressor kicked in the ground circuit would complete and the fans would come on in series. This was basically to get extra ice cold air from the A/C as it gets pretty hot here and stays that way !
HMMM, I would really like to do that to mine next summer.

Just to clear it up, the fans are supposed to come on with the a/c, but never really do (almost not needed). However, they will come on when the engine temp reaches a critical level to prevent the engine from frying.
 

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Well not exactly. When the A/C ecu detects the temp going up a certain point the fans are "supposed" to kick in and same thing with engine temp the engine ECU. After I fans started to work on my first bio. I clearly remember them staying on for quite some time even after the car was switched off. But I only remeber witnesses this only once.

As for the jumpering if the Binary Switch its a 5 min job, I just used a very teensy bit of thin welding rod stick bent into a U and stuck it in there and taped it up nice and cable tied it with something up there facing up so it would not dangle and moisture and dust not get in it. Same with the plug where the switch plugs into the bottle ( again dryer ? )

Worked perfectly on all my 3 RR's the fans with switch on and off in sync with the compressor.
 
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