Want to replace the air conditioning heater control unit (Scenic)

What have you checked so far ?
Radiator full of coolant ? Heater hoses getting hot ?

I'm making some assumptions, here.. I've been told I make too many assumptions... but, I'm assuming that you're talking about the engine cooling fan.. If I'm correct in this assumption, my guess is that you've not taken the vehicle to a good, reputable mechanic or repair shop. There are several reasons that an engine fan would not turn off, and each reason would have to come from a qualified mechanic. For example, there is a sending unit for the air conditioning system that might cause continuous running... or a sending unit in the air conditioning system that could cause the same thing. To complicate that issue, quite likely your air conditioning system purposely kicks on the engine fan any time you run your defroster. Also, your inside heater should function correctly, regardless of the engine fan running continuously. If I'm wrong on that score, then your engine has a thermostat problem "to boot"... which, by itself, could cause poor heating of the inside of the vehicle. NOW, backing up a little, if you so happen to be talking about the fan INSIDE the vehicle that is part of your heating OR air conditioning, we have a little different matter on our hands... First, some vehicles legitimately have a fan running on slow speed at ALL times.. for continuous air circulation purposes (sometimes, you can't actually hear this). Also, I might add that THIS fan running all the time should not be a problem for the heater to work properly.

put a radiator flush in the expansion bottle .to clean the core of both your radiator and your heater. core will have dirt or rust .run the car for about 20 miles.then drain it .refill with 50/50 mix of anti freeze.now heating on full leave the cap off .turn over the engine,on tick over.push in the rubber hose with finger and thumb to remove the air out the bottle.then refit the cap.

Does the fan stay on even with the ignition key off? Do you have automatic heating and air conditioning controls? Automatic controls have a light up blue screen in the middle of the temperature controls, and there will be a button that says "Auto". If you do have automatic controls, the likely culprit of your fan staying on constantly is what is called the blower control processor. The blower control processor is a small computer that replaces the blower resistor commonly found in cars. When the blower control processor fails, it usually "sticks" on. It's not a cheap part, but is easy enough to replace if you're handy with basic hand tools and comfortable unplugging electrical connectors under the glove compartment area.

over heating

It would be best to start by having DTC'S - diagnostic trouble codes checked ! Dealer or someother qualified shop that has a professional type scan tool , autozone or any other part store's tool will not read these codes .

DTC B1310 Ambient Air Temp Sensor Open Circuit
DTC B1311 Outside Air Temp Sensor Short Circuit
DTC B1312 High Side Temp Sensor Open Circuit
DTC B1313 High Side Temp Sensor Short Circuit
DTC B1314 Evaporator Inlet Temp Sensor Open CKT
DTC B1315 Evaporator Inlet Temp Sensor Short CKT
DTC B1316 In Car Temperature Sensor Open Circuit
DTC B1317 In Car Temperature Sensor Short Circuit
DTC B1318 Sunload Sensor Open Circuit
DTC B1319 Sunload Sensor Short Circuit
DTC B1340 Air Mix Door #1 Movement Problem
DTC B1341 Air Mix Door #2 Movement Problem
DTC B1347 Very Low A/C Refrigerant Warning
DTC B1348 Very Low A/C Refrigerant Pressure
DTC B1350 Engine Coolant Over-Temperature

Air Temperature Control Inoperative - Passenger

Circuit Description
The heater and A/C programmer receives the requested temperature offset on CKT 831 (DK BLU/WHT) from the passenger climate control. The heater and A/C programmer controls the on and off status of the passenger climate control on CKT 1336 (DK BLU).

Test Description
Checks the temperature control (full hot) of the Passenger Climate Control. Also verifies the condition of CKT 831.
Checks the temperature control (full cold) of the Passenger Temperature Control. Also verifies the condition of CKT 831.
Checks the ON/OFF switch of the Passenger Temperature Control. Also verifies the condition of CKT 1336.
Checks the ON/OFF switch of the heater and A/C programmer. Also verifies the condition of CKT 1336.
Checks terminal condition of the heater and A/C programmer.

Do you know how to do automotive electrical testing ???????


1
Turn the ignition to the ON position.
Turn the passenger climate control to full hot.
Measure the voltage at terminal D13 of the heater and A/C programmer.
Is the voltage measured equal to the specified value?
12 V
YES - Go to Step 2
NO - Go to Step 8
2
Turn the passenger temperature control to full cold.
Measure the voltage at terminal D13 of the heater and A/C programmer.
Is the voltage measured equal to the specified value?
0 V
YES - Go to Step 3
NO - Go to Step 8
3
Press and hold down the passenger temperature control.
Measure the voltage at terminal C16 of the heater and A/C programmer.
Is the voltage measured equal to the specified value?
0 V
YES - Go to Step 4
NO - Go to Step 9
4
Release the passenger temperature control.
Measure the voltage at terminal C16 of the heater and A/C programmer.
Is the voltage measured equal to the specified value?
12 V
YES - Go to Step 5
NO - Go to Step 9
5
Turn OFF the passenger temperature control.
Measure the voltage at terminal D10 of the heater and A/C programmer.
Is the voltage measured equal to the specified value?
12 V
YES -- Go to Step 6
NO - Go to Step 10
6
Turn ON the passenger temperature control.
Measure the voltage at terminal D10 of the heater and A/C programmer.
Is the voltage measured less to the specified value?
12 V
YES - Go to Step 7
NO - Go to Step 10
7
Inspect the terminal contact at the heater and A/C programmer.
If OK, replace the heater and A/C programmer. Refer to Programmer Replacement
Is the repair complete?
--
System OK
--
8
Inspect CKT 831 (DK BLU/WHT) for an open or short.
If OK, replace the passenger temperature control. Refer to Control Assembly Replacement - Passenger
Is the repair complete?
--
System OK
--
9
Inspect CKT 1336 (DK BLU) for an open or short.
If OK, replace the passenger temperature control. Refer to Control Assembly Replacement - Passenger
Is the repair complete?
--
System OK
--
10
Inspect CKT 1370 (PPL) for an open or short.
If OK, replace the passenger temperature control. Refer to Control Assembly Replacement - Passenger
Is the repair complete?
--
System OK
--

hi everyone my wifes renault scenic fan switch that controls the speed of fan wont work so no heater ive checked the 40a fuse and its ok just wondering if any one knows why its suddenly stopped thanks

is the temp gauge working? sounds like coolant temp sending unit... or a possible engine coolant temp sensor or ect sensor.

9 times out of 10 on this old of vehicle its the heater core. If your car temp gauge is working and the car is heating up fine and the blower works then it is most likely your heater core. Not sure how hard it is on that car. SOme times it just under the dash takes about 30 mins but some cars you have to pull the dash out. The part alone is cheap. I would try logging onto autozone.com put in your car find the part (heater core) then look at the how to change section of auto zone.

Goodluck.