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1995-2002 Range Rover P38A
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145 Posts
Discussion Starter #1
Does anyone know what the resistance value (Ohm) for a good evaporator sensor (STC3365) and for the Heater sensor (STC3256) should be?.

I get no reading when i measure them so no contact between the two pins.

My airco stopped working.
i did test the compressor and relay 3 there ok.
could also be the pressure switch
I've been having the book symbol for years now but all worked except the blend motors are stuck every once and awhile. Have some new ones but no time to place em yet :)
 

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1995-2002 Range Rover P38A
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1,851 Posts
Hi

The evaporator temperature senor is used by the ECU to prevent freezing of the unit by switching off the AC compressor when the temperature gets too low. The heater sensor does not have much influence on the AC operation. I have the heater disconnected for years without any problems other then the book sign.

Regards

Jos
 

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1995-2002 Range Rover P38A
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145 Posts
Discussion Starter #3
Hy Jos,
I Know but if there defect i might as well replace them, i just don't know how to find out if they're ok or not without a trip to the stealer.
Thinking i could measure them with an Ohm meter.
But They both gave no connection.
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,199 Posts
If they have no connection, then they're not working - simple as that.

I'm away at the moment, but will have a look in my notes when I get home tomorrow.. I changed my heater temp sensor awhile ago because it came back as no connection - but I can't remember if I measured the resistance of the new one before I put it back in. If I did, it will be written down, and I'll post it up.

Cheers,
Marty

Sent from AutoGuide.com Free App
 

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1995-2002 Range Rover P38A
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Discussion Starter #5
Hy Marty_nz,
anxiously awaiting your reply.
I did order new ones, if you did not measure them i will.
could be handy data for others.
Thanx
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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Hi efarmer,

Got home this evening and have had a look through my notes...
I haven't got anything on the resistance values of the new sensor I installed... The only values I had were from when I replaced the throttle position sensor on the engine... I think I was in a hurry to get the HEVAC/dash back in place as I was losing light when I re-installed the sensor...

If you don't mind putting the values you get up, it might give a reference to someone else in the future!

Cheers,
Marty
 

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1995-2002 Range Rover P38A
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145 Posts
Discussion Starter #8
I finally received the new sensors
but when i measure them i get no reading like there is no connection.
is that ok???:shock:
2013-06-10 10.25.10.jpg
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,199 Posts
You'll need to switch the multimeter to either the 20K or 200K range, as the sensors are quite high resistance.

Their resistance decreases as the temperature goes up. RAVE lists the ambient temp sensor (that's by the radiator) as being about 12.5K ohms at 20 degrees C. I don't know if that value is the same for the other temp sensors (RAVE doesn't list resistance values for any of the others) but you should see a reading if you switch the multimeter to the 20K range.

Cheers,
Marty
 

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1995-2002 Range Rover P38A
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145 Posts
Discussion Starter #10
Hy Marty,
Thank you that's it !

for the Evaporator sensor (STC3365) it's about Ohm 5,74/20K range
the Heater sensor (STC3256) is Ohm 27.2/20K range



Thank you
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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Roughly what temperature were the sensors measured at (being as they change resistance depending on temp - it's useful to have a base line temp and resistance value...)

Also, are you sure the 27.2 was on the 20K range? or was it on the 200K range? I wouldn't have expected to see 27.2 K ohm on 20K range.. but maybe I'm wrong!

Hopefully the new sensors will get the HEVAC up and running again for you!

Cheers,
Marty
 

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1995-2002 Range Rover P38A
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145 Posts
Discussion Starter #12
yep 20K temperature was 18 deg. celsius

only my heater sensor was defect
i don't think this will have solved my aircon problem.
could not really test it because of outside temp was like 16 deg celsius
 

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1995-2002 Range Rover P38A
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Discussion Starter #13
Ok i went to the airco guy
No pressure in aircon system
becouse of a leak in my condensor
he is going to replace my condensor on monday.
and told me it's best to also replace the dryer.
 

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1995-2002 Range Rover P38A
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Hi

He is right about changing the dryer also. It is good practice to vacuum the system and flush it with nitrogen before the new refridgerant gas is charged. These steps will ensure that all moisture is removed from the system. The dryer is a chemical way of bonding any water. If the system is leaking it means this chemicals have been exposed to air and moisture and are probably saturated with water.
Water present in the system will mess up the pressure readings, makes the system less economical and above all it can cause ice in the expansion valve causing blockage and irregular operation of the whole system.

Regards

Jos
 
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