Heater woes
 

Hi all,

Hoping someone can help with my heater problem.

2 weeks ago, 4 hours into a 5 hour journey the heater on my XC70 (2007 Auto) suddenly went cold on both sides. Pouring wet night, stopped quick look under bonnet all looked good, no coolant loss, temp gauge normal. carried on. Following day checked coolant. All ok. Done a bit of running around, heater working fine. This was the norm for the week. However on return 5 hour journey after 3 hours heaters went cold. Stopped checked, all ok. 20 minutes later, 'low coolant, stop engine blah blah'. Stopped, found coolant escaping from split hose on Rh of engine (facing it). Temp gauge still at normal. Relay home, garage fixed pipe, but no heaters. All flaps move (I can hear them) car runs fine, no coolant loss. Took dashboard apart and cleaned the sensor and fan. Still no heaters.

Any help appreciated

Cheers

How many miles on it ? Do you remember which hose split ? On the ail filter side we have both small hoses going to the heater, and also the large lower radiator return hose. To me the whole thing seems strange, thinking maybe some deposits from inside the engine cooling channels detached all of a sudden and went blocking the heater core ? Could have helped to carefully touch the two heater hoses see how hot were these

Hi.

Thanks for your reply. Car has 150 thou. Should have said in original post, hose was on the right as you face the engine, short about 6 inches long and bent at right angles. Both heater hoses are not which makes me think flow is ok. Thinking there are two unrelated faults throwing up a red herring. Just the fact the heater packed up, came back then packed up making me think electrical. Any suggestions, thoughts appreciated.

Cheers

There is a sensor (a thermistor) in the AC panel (behind the small slatted hole) that monitors the current cabin temperature. If the cabin temperature is greater than or equal to the temperature selected on the panel then no heat will be provided.

The thermistor can go bad and send a high cabin temp signal to the CC module so you never get any heat. Ideally, connect VIDA to the car and you can read out what the CC module thinks the current cabin temperature is.

A quick and dirty test is to set the heater to Max Hot both sides. This should override the thermistor value and always provide heat regardless of current temperature.

If this test works then replacing the thermistor is straightforward and cheap and covered on other threads. You can check before replacing it that it isn't bunged up with dust and dirt.

Same problem here. Must try this.