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Discussion Starter #1
Anybody had a similar problem and had a correct diagnosis?

In the last week or so, I've been having problems with my HVAC system. The heating system has been blowing cold intermittently. The water temp gets upto 90 in normal time, about 5 mins after setting off, but the heaters continue to blow cold even when heating temp set to 30+.

After a while the water temp will go above 90, I'll stop the car it will come back down to 90, I'll set off and the water temp will then drop briefly to about 80 and then back up to 90. The heaters will then blow hot for a minute or so and go back to cold.

The process of water temp dropping down to 80, back to 90, heaters blow hot and then cold again, will cycle for about 25/30 minutes and after that the heating will work fine.

Any ideas? Blockage? Dodgy thermostat? Temperamental water pump?

Additional info:
- I'm not loosing coolant, so don't think its head gasket (plus had that changed about 6 months ago)
- When the heating is fully functional after 30 mins, if I set the heating system to 'Auto' the fan speed increases unnecessarily.
- I've had a lot of cooling system problems over the last year or so, but these were all covered under warranty which has now finished. The sign that led the dealer to change the head gasket, was that I was loosing coolant and the heaters were blowing cold constantly.

Any help would be very useful.
 

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Discussion Starter #2
Some googling has thrown this out....

"Then again, if your thermostat is stuck partially or completely open, you will have the same symptoms as an incorrect thermostat. Unfortunately, a thermostat that is stuck only slightly open will cause double trouble. It will make the engine take much longer to warm up, but may not allow enough coolant to flow at high speed to keep the engine cool and might cause an overheating condition."

Sounds plausible. Can anyone indicate where I'd find the thermostat on a 2.0 JTDM2 Giulietta engine?

Thanks
 

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I'm thinking water pump impeller loose, or the coolant level is low. but you say coolant level is fine...


did you try with the temp set to "high"? the heater will not look at inside temp sensors and will blow as hot as it can. if you get hot air then, it's an electronics issue.
 

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My heater fan likes to give itself a good run before it settles down.....and this happens daily. I don't know whether its the AQS getting rid of impurities in the air or what, but after about 5 minutes it all settles down.
 

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My heater fan likes to give itself a good run before it settles down.....and this happens daily. I don't know whether its the AQS getting rid of impurities in the air or what, but after about 5 minutes it all settles down.
I think you'll find that's normal as mine does exactly same - although rather less on these warmer mornings.
 

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I think you'll find that's normal as mine does exactly same - although rather less on these warmer mornings.
Yep, you're right Argo and I do expect it.
 
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