My son's 08 has a clogged heater core that we flushed yesterday but didn't work. Has anyone had to flush it more than once? It got warmer while we were flushing but then went right back to cool when we filled it with coolant.

 

Sounds like a stuck thermostat.

 

take out the thermostat, you'll probably be surprised what you find

 

Does the car warm to the normal operating temp?

Check the heater temp control **** operation. Make sure it is switching from hot (red) to cold (blue).

Turn ignition to ON position. Turn on radio. Press and hold the radio ON/OFF button down and then depress SCAN up button. Radio display should change and display the word TEMP and a number between 0-16. 0 being cold and 16 being hot.

Rotate the temp control **** from cold to hot and the number value in the display should change.

If the number does not change during this procedure then the problem is in the temp control ****.
Try lifting upwards on the **** as you turn it. Just a little pressure upwards. See if it works then.

 

Thanks, temp control **** checks out fine. Thought about thermo but the car operating temp is same as it ever was. We have had days below zero and 40 with no diff. Is it a 180* thermo?

 

I get heat only on the passenger side. I flushed the core to no avail.

 

I have an '04 that blows lukewarm air when turned all the way up. This past weekend, I flushed the coolant system (and backflushed it) to try and clean out the built-up gunk in the heater core. Unfortunately, nothing changed. I have checked the thermostat and though it is not working 100% correctly at changing the temperature, it switches between either full hot or cold.

My next DIY fix will be to fix the wiring to the temperature gauge behind the radio, and I am curious if it would be a good time to replace the heater core as well? Also, does anybody know where to buy one other than my local Mazda dealership or should I just save myself the hassel and pay to have it replaced?

 

Not sure why you think the heater core is plugged...unless someone filled it with tapwater and very little coolant and left it for years...or mixed uncompatible coolants together...your coolant shouldn't plug up the heater core

There are lots of more likely reasons you don't get heat.....most are electronic

 

Agree with Dan, although there have been many with Heater Core (Radiator) blockages/issues.

I would make sure your electronics hot/cold are working correctly...Your HVAC unit could have electric contact issues, known in earlier Series 1's.