Temperatures have dropped in VA this week and I find that I'm getting no where near the amount of heat from the heater/defroster as compared to before. Coolant level is between low and high, temperature gage reads in the center after warmup (when it is intermittently working) and car drives normally. I replaced the head gasket about 70K miles ago. Fan works normally and I can get air flow from vents as selected (floor, defrost, direct etc.)

I suspect the heater control valve and have a spare on hand. I plan to replace it this weekend. Is there anything else I should check?

Clogged heater core?
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Will I buy another Volvo??? We'll see....

Good point, I will try to flush the core out when I check out the heater valve.

If you can let it sit overnight. I've used this method countless times works well. Flush and back flush. Then pour some white vinegar into the core. Let it sit overnight. Then flush again. To save some time trying to get all the air out. Pour antifreeze into the core before you put the hoses back on.
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Post Back. That's whats makes this forum work.

Well I lucked out. The old heater valve was pretty gunked up. Replacing it with a new one from IPD did the trick. Back to volcano heat output.

The first job I did on the car when I got it about 10 years ago was to replace the heater core so luckily that didn't seem to be the issue this time.

Thanks for the tips.

Brian Mee

Manassas VA

Dear BrickDad,

Hope you're well. Glad to hear that the heater core was not the problem. Was the "gunked-up" heater control valve installed when you replaced the heater core? Or, was the failed heater control valve the factory-original item?

Yours faithfully,

Spook

I always keep a spare valve in the car in case the 1 in use breaks.