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[Solved] Peugeot 307 2.0 16V 2003 - Warm air supply is working / not working

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  • #1 16959116
    obadaw
    Level 7  
    Posts: 83
    Rate: 18
    Hello

    I have a question, I haven't met anyone with such a problem yet, that's why I'm writing.
    Namely, for a few days I was driving at full 28 degrees with the air supply on and it was so hot on average: on the driver's side, on average, on the passenger's side a little better. After a few days, only the cold air on both sides stopped heating. After a while, some flashes of warm air began to emerge from the vents again. The fan works properly because its blowing force reacts to increasing and decreasing the airflow level.
    What's more, the car heats up to 90 degrees without any problems and keeps the temperature. The thermostat is also OK
    The heater does not spit liquid, so I assume it's working.
    I would like to add that when I had an Audi before, when I gave it full heat, I could not hold my hand in the airflow because it was so hot, and in this car I do not know how much I would have to hold my hand in the airflow to warm up.

    Any ideas, why is this happening and it does not heat so well?
    Thank you in advance for your help.
    greetings
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  • #2 16959251
    Pedros050
    Level 43  
    Posts: 17906
    Help: 2471
    Rate: 3901
    Hello. Air in the heater or there is a need for replacement, the coolant does not circulate fully throughout the heater.
  • #3 16959264
    obadaw
    Level 7  
    Posts: 83
    Rate: 18
    The coolant was replaced because the entire water pump was replaced with a new one along with the entire agent.
    After replacing this pump with a new one, everything was as hot as before the replacement, i.e. without changes. only now such problems have arisen.

    Ps. How to bleed such heaters?
  • #5 16959293
    Pedros050
    Level 43  
    Posts: 17906
    Help: 2471
    Rate: 3901
    How do you heat the engine, have both 2 hot pipes from the heater, inlet and outlet?
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  • #6 16959299
    obadaw
    Level 7  
    Posts: 83
    Rate: 18
    I haven't been able to check that yet
    Added after 40 [minutes]:
    I found this valve, the heater was not air-tight, because as soon as I unscrewed the cap, the liquid ran out.

    PITERRR wrote:
    How do you heat the engine, have both 2 hot pipes from the heater, inlet and outlet?

    PITERRR when it comes to these 2 hoses from the heater, both hoses are warm (not hot) after heating the car
  • #7 16973566
    obadaw
    Level 7  
    Posts: 83
    Rate: 18
    Hello

    I replaced the thermostat, the temperature inside the car changed. It is much warmer than before, but now I have a problem because it is much weaker on the passenger side than on the driver's side.
    Cool air flows from the vents instead of warm air.
    Any ideas what could be the reason for this because I don't know anymore ??
  • #8 16973625
    Pedros050
    Level 43  
    Posts: 17906
    Help: 2471
    Rate: 3901
    The air supply flaps do not work and the air flows from outside and not through the heaters.
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  • #10 16973840
    Pedros050
    Level 43  
    Posts: 17906
    Help: 2471
    Rate: 3901
    First, undress so that you can see what is happening and then you will buy or order?
  • #11 16973869
    obadaw
    Level 7  
    Posts: 83
    Rate: 18
    Do you have a manual how to get to such an actuator from the passenger side ??

    Added after 19 [hours] 27 [minutes]:

    Peugeot 307 2.0 16V 2003 - Warm air supply is working / not working

    A little update, I got to these modules. And both of the modules shown in the picture work properly after changing the heating.

    The photo does not show 3 which is even higher. But if this is this module, which one controls the temperature, which one to turn on?
  • #12 17070751
    obadaw
    Level 7  
    Posts: 83
    Rate: 18
    Hello again, today I checked all the heater's motor regulators and they all work properly, they are not broken or the tips are machined.

    So it probably remains to replace the fuser, right?
  • #13 17070781
    Pedros050
    Level 43  
    Posts: 17906
    Help: 2471
    Rate: 3901
    If it does not heat up, check what are the heater hoses, especially on the return, if hot, then rather functional. If it is summer, there is no circulation to replace it or it is stony and heats poorly.
  • #14 17070873
    obadaw
    Level 7  
    Posts: 83
    Rate: 18
    ok, next week i will start replacing it, let you know how after the exchange.

    Because when it comes to the temperature of this two-tube, both wires are equally warm (at least I think so)
  • #15 17087210
    obadaw
    Level 7  
    Posts: 83
    Rate: 18
    Hello

    The replaced heater with a new twin-pipe that goes directly to it. The heat returned :)
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Topic summary

✨ The discussion revolves around a heating issue in a 2003 Peugeot 307 2.0 16V, where the user experiences inadequate warm air supply from the vents. Initially, the air was hot, but it later transitioned to cold air on both the driver and passenger sides. The user confirmed that the coolant was replaced and the thermostat is functioning correctly. Responses suggest potential causes such as air in the heater, improper coolant circulation, or malfunctioning air supply flaps. The user later replaced the thermostat, which improved heating on the driver’s side but left the passenger side cooler. Further troubleshooting indicated that both heater hoses were warm, and the user replaced the heater unit, which restored heat. The discussion includes inquiries about bleeding the heater system and checking the actuator for air supply control.
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FAQ

TL;DR: Peugeot 307 weak/no heat often traces to air in the heater, stuck blend flaps, or a clogged heater core; check the 2 heater hoses first. “Have both 2 hot pipes from the heater?” [Elektroda, Pedros050, post #16959293]

Why it matters: This FAQ helps 2001–2008 Peugeot 307 owners quickly diagnose uneven or no cabin heat without guesswork.

Quick Facts

Why does my 307 blow warm, then cold, then warm again?

Air trapped in the heater circuit can cause intermittent heat. Flow surges move bubbles, so outlet temperature swings. A partially restricted core can mimic this. Purge air and verify circulation before chasing electronics. "Air in the heater or there is a need for replacement" is a known pattern here. [Elektroda, Pedros050, post #16959251]

How do I bleed the Peugeot 307 heater circuit?

Use the bleed point on the heater line. 1) Warm engine, set heat to max, blower on low. 2) Crack the bleed cap until coolant flows steadily without bubbles. 3) Top up coolant to spec, cap, and recheck after a drive. The user confirmed coolant immediately exited when the cap was opened. [Elektroda, obadaw, post #16959299]

Both heater hoses feel warm, but the cabin is still cold—what next?

Equal hose warmth does not guarantee sufficient flow. Inspect for partial blockage in the core and confirm return-line temperature under load. If return cools rapidly or airflow stays cold, suspect a restricted core or internal scaling. Replace the core if circulation is weak. [Elektroda, Pedros050, post #17070781]

Why is the passenger side cold while the driver side is warm?

A blend-air flap is not routing air through the heater matrix on one side. The actuator may be jammed, out of calibration, or its door is broken. "The air supply flaps do not work and the air flows from outside and not through the heaters." Inspect actuators and flap shafts before replacing parts. [Elektroda, Pedros050, post #16973625]

Should I buy a flap actuator or a repair kit first?

Do not buy parts blind. Expose the HVAC box and observe actuator motion while changing temperature. Repair kits help when flaps crack or slip. Replace the motor only if it fails to move or calibrate. "First, undress so that you can see what is happening and then you will buy." [Elektroda, Pedros050, post #16973840]

How many HVAC actuators are on the passenger side, and which one handles temperature?

Expect multiple actuators; the user identified two in view and noted a third located higher. Temperature control uses the blend actuator linked to the heater flap. Trace the lever connected to the heater box to find it. This car showed three modules in that area. [Elektroda, obadaw, post #16973869]

What finally fixed the weak/no heat in this thread?

Replacing the heater core along with its twin-pipe feed restored full heat output. After earlier checks and actuator tests, this hardware change resolved the cabin temperature issue completely. The owner reported, "The heat returned." [Elektroda, obadaw, post #17087210]

How can I tell if the heater core is clogged versus an actuator fault?

If actuators move correctly but heat is weak or uneven, feel the return hose during a steady 2,000 rpm hold. A notably cooler return or slow warm-up suggests restriction. If both hoses stay only lukewarm, flow may be insufficient due to scaling. Replace the core if flushing fails. [Elektroda, Pedros050, post #17070781]

Can a thermostat cause poor cabin heat on the 307?

Yes. A stuck-open thermostat lowers coolant temperature to the heater. In this case, replacing the thermostat improved cabin temperature, but a side-to-side split remained, pointing to flaps or the core. Thermostat fixes general warmth, not distribution. [Elektroda, obadaw, post #16973566]

My fan works but air stays cool—does that rule out HVAC faults?

No. Blower operation only proves airflow, not heating. You can have a strong fan with cold air when coolant flow is poor or blend flaps bypass the core. The user noted the fan reacted correctly while heat was inconsistent. [Elektroda, obadaw, post #16959116]

What is a blend flap actuator?

It’s a small electric motor with gears that positions internal HVAC doors to route air through or around the heater core. Faults cause wrong temperature or distribution. The user considered both a repair kit for flaps and a used actuator when diagnosing. [Elektroda, obadaw, post #16973828]

What is the heater core and twin-pipe on a 307?

The heater core is a small radiator inside the dash. Hot coolant enters via a twin-pipe assembly, transfers heat to air, and returns to the engine. Replacing both restored normal heating in this case. [Elektroda, obadaw, post #17087210]

Is 90°C engine temperature normal for good cabin heat?

Yes. The owner reported the engine reached and held about 90°C. That’s sufficient for strong heater output if flow and flaps are correct. If heat is weak at this temperature, focus on air bleeding, the core, and the blend system. [Elektroda, obadaw, post #16959116]

Edge case: both hoses hot, passenger cold, actuators move—what then?

The flap door can crack or slip on its shaft, so the actuator turns but the door doesn’t. Use a repair kit or fix the door interface. Visually confirm door movement, not just motor motion, before closing up. [Elektroda, obadaw, post #16973869]

Quick 3-step diagnostic for uneven heat on a 307

  1. Feel both heater hoses at operating temp; note inlet–return difference. 2. Watch blend actuators while changing setpoint. 3. If flow is weak or split persists, bleed and, if needed, replace the heater core/twin-pipe. [Elektroda, Pedros050, post #17070781]
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