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  #1  
Old August 22nd, 2009, 09:16 AM
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Rich Campbell
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Running Hot with a/c on

Hi all.

My 90 (97) is running hot sometimes when I have the a/c on, other times it is fine. The cooling fan in the front of the radiator is working on and off. Almost like it has a thermostat switch. When ever it gets hot I notice the fan isn't running. Anyone have a picture of where this switch is on a 97? and how to switch it out.


Thanks a always.
Rich
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  #2  
Old August 22nd, 2009, 09:55 AM
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There are two switches. One, which seems to be working, kicks in when the coolant temp gets pretty hot, the other turns it on whenever the ac is on. Not sure where that second switch is on a 1997.
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Old August 22nd, 2009, 10:29 AM
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Rich Campbell
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Thanks Ron....Hopefully someone here will know.

Follow-up Post:

It seems to turn on when the a/c is put on. Then it just turns off for no reason and the truck gets hot.
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Old August 22nd, 2009, 11:07 AM
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"Then it just turns off for no reason and the truck gets hot."

Fan needs to be replaced. The motor in it is likely seizing up when hot.
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  #5  
Old August 22nd, 2009, 11:09 AM
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Quote:
Originally Posted by Campbell
Thanks Ron....Hopefully someone here will know.

Follow-up Post:

It seems to turn on when the a/c is put on. Then it just turns off for no reason and the truck gets hot.
Rich,

I'm having a similar issue with my truck. It get's hot with the A/C on and driving at slow speeds or at idle. As far as the A/C condensor fan switch, on the 94/95 it's located on the thermostat housing, and I'm sure you've looked on your 97 there isn't a spot on the thermostat housing for that switch. My guess after talking to a few folks is that the A/C condensor fan is controlled via the Coolant temperature sensor which sends a signal to the ECU which controls the A/C condensor fan based on temperature. I don't believe it is wired to come on when the A/C comes on. I could be totally wrong with this as I'm still in the process of trouble shooting my problem, but that's the path I'm going to take. I'll let you know what happens with mine.

Noel
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  #6  
Old August 22nd, 2009, 11:14 AM
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Noel,

That sounds possible, but I am fairly certain there are two switches (this, I suppose, could be a 94/95 thing and 97 is different), but on my two 94s I had and on my 95, the fan is always on full time if the AC is on so I don't think a temp switch would cause the fault Rich described. However, to test your theory, Rich could wait until the fan stops with the AC on and see if power is coming to it or not with a test light or multimeter.
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  #7  
Old August 22nd, 2009, 12:28 PM
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Good idea......with the test light.

My fan is not running the whole time the a/c is. It turns on and off.
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Old August 22nd, 2009, 01:04 PM
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pls report back with results.
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  #9  
Old August 22nd, 2009, 01:22 PM
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On a 97 the fan is controlled through the ECU via a relay located on the right side of the A/C blower assy. (inside the truck in front of and below the passengers right knee) . The relay is behind a black plastic cover secured by 2 or 3 screws. When the A/C is switched on it sends a request to the ECU to switch the fan on. If several other parameters are met the ECU will ground the relay and switch the fan on. (Through a gry/wt wire….i think)



To check if it is a fault with the condenser fan motor you can wire a test light up to illuminate whenever the ECU is “granting” the fan relay ground. If the light comes on the fan should be on too. The relay is the forward most of 3 relays behind the cove.
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  #10  
Old August 22nd, 2009, 02:09 PM
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Thanks.

The fan motor seems to be working ok. It is just being told to turn off when it should be on for some reason. Could a bad relay be causing this? If so do you know what the relay is and where I can order one.
Thanks
Rich
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  #11  
Old August 22nd, 2009, 11:45 PM
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You should be able to pick the relay up at any auto parts store as it is not a Land Rover specific part. Pull the old one out and take it in with you.



The ECU could be turning the fan off if one of the other parameters I mentioned earlier is not met. I don’t have it in front of me but I think it receives signals from the trinary pressure switch to check that the system is within pressure limits and also from the compressor to check it is running (clutch engaged).



Is your thermostat set to the coldest setting? When the compressor cycles off during normal operation the condenser fan should also cycle off.



Lots of guys just install an additional relay under the hood somewhere wired to the fan through an interior on off switch. This way you can simply turn the fan on any time you want for additional cooling. Note that the ECU will also switch the fan on any time coolant temperature goes above 228F



Hope this helps. I’m fighting overheating problems myself so I have just gone through this.



V/R
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  #12  
Old August 23rd, 2009, 07:33 AM
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Thanks I will let you know how I make out today!

Rich
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  #13  
Old August 23rd, 2009, 07:07 PM
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Well, I replaced the relay and it didn't help. Same thing happened today. Fine on highway but whenever I run the a/c it works fine then out of nowhere the temp runs hot. When I inspect the fan it is off when the truck runs hot. I was hoping it was something simple as a temp sensor but can't find any.

Holding off replacing the fan until I have tried everything.

Thoughts??

Thanks
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  #14  
Old August 23rd, 2009, 09:24 PM
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Is there power to the fan when it shuts off?
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  #15  
Old August 23rd, 2009, 10:10 PM
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Jim Cheney
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Make sure you don't have a ground fault of some kind. Its easy to cause a temp guage to read hot if it is grounded wrong. Leave the AC off, but turn on headlights, wipers, and any other electrical accessories and see if using electrical accessories causes the temp to spike. If that does it, then you have a gauge problem and not an AC problem.
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  #16  
Old August 24th, 2009, 07:00 AM
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Thanks guys.....I will test both tonight and let you know.



Rich
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  #17  
Old August 25th, 2009, 06:02 PM
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I did what you suggested and turned on all the power I could and the temp gauge went up. When I turned the lights off it came down a bit.

What do you think??
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  #18  
Old May 11th, 2011, 12:22 PM
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Thread resurrection alert!

Finally some hot weather in Chicago, and even with the top off, the interior of the truck is noticeably HOT. Is this normal? I had the bulkhead vents open even, but it didn't stop the heat radiating from the front.

I switched the A/C on and watched the temp gauge creep past the half-way mark. I checked the fan on the front, and it was not on. I bench tested it, and the fan does work. Maybe a bad relay? Where is that?

Any other solutions to

A) Mitigating the heat radiating into the driver's area
B) Figuring out how to cool the engine, especially when the A/C is on
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  #19  
Old May 11th, 2011, 02:39 PM
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Fighting this one as well. I have a 94 and just had the Radiator recored to a three core and replaced the viscous clutch. Everything seems to be fine at speed when pushing air through the engine compartment, but at idle or in traffic the temp rises...

Waiting to hear ideas.
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  #20  
Old May 11th, 2011, 02:56 PM
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John - So does that mean I shouldn't re-core my radiator if the mechanic recommends it? What's a viscous clutch?

What symptoms was your truck exhibiting that caused you to do those things?
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