Intermittant heat even when set to HI

[truck11]

HVAC unit was set to 'HI' and intermittently blows warm air. I turn it down to normal temp of say 74 and blows cool air. Turn it up to 80 - may blow warm air - turn to hi and warm, briefly hot - then minutes later was just warm. Fan speed is on high
Outside temps in the 40's - 2 1/2 hr drive home from Philly Christmas Eve was very frustrating trying to get vehicle cabin comfortable. Also seems to take longer to warm the cabin up in the mornings.

We recently (2+ months ago) changed the radiator due to a leak along with the thermostat. Everything seemed to have been working up until last week. Not sure if they are related but wanted to mention it here as that was the last thing done to the vehicle.

Engine seems to come up to normal temp as expected. Not sure whats going on with the HVAC though.

Any thoughts?

Thanks
Julian

[rocky]

Start by checking the coolant fluid level. I suspect it is low, causing an air bubble in the system. The air bubble stops or limits the flow of coolant to the heater matrix

Refill only with Honda coolant fluid.

[truck11]

Rocky - why ONLY Honda coolant? I don't think they used Honda coolant when they replaced the radiator.
I checked the level this AM and it was low - I will refill this evening (Wife's car).

[KKL]

Originally Posted by truck11

Rocky - why ONLY Honda coolant? I don't think they used Honda coolant when they replaced the radiator.
I checked the level this AM and it was low - I will refill this evening (Wife's car).

Looks to me like either they did not completely fill the system after the radiator job or there is still a leak somewhere. It is basically a closed system and the coolant does not just disappear.

Here's my PERSONAL preference on what coolant to use. My '06 is past the warranty mileage limit. I would go with the undiluted Prestone Any Make/Any Color Extended Antifreeze for $10.50/gallon from Walmart. For more savings, get the Walmart Super Tech Antifreeze for $9.50. In this area, the Walmart antifreeze is made by Prestone (you can tell by the labeling and the ingredient list).

[rocky]

From following this forum for a while, reduced silicates and other abrasive stuff.

[truck11]

system has been flushed again, replaced the water control valve ($15 part that we needed to bypass to check anyway - so replaced it) still no heat.
Going to check the in/out coolant hoses with laser temp gauge when I have a moment to see if we actually get movement/see if there is any difference.
Other than that - I am stumped. Engine temp comes up to 'normal' pretty quickly but still no heat out of the vents.

Any other thoughts?

[75blazer]

I don't know if you've solved this yet, but the fix in this thread solved my problem.

No heat in front console

[ptsmh73]

Originally Posted by truck11

HVAC unit was set to 'HI' and intermittently blows warm air. I turn it down to normal temp of say 74 and blows cool air. Turn it up to 80 - may blow warm air - turn to hi and warm, briefly hot - then minutes later was just warm. Fan speed is on high
Outside temps in the 40's - 2 1/2 hr drive home from Philly Christmas Eve was very frustrating trying to get vehicle cabin comfortable. Also seems to take longer to warm the cabin up in the mornings.

We recently (2+ months ago) changed the radiator due to a leak along with the thermostat. Everything seemed to have been working up until last week. Not sure if they are related but wanted to mention it here as that was the last thing done to the vehicle.

Engine seems to come up to normal temp as expected. Not sure whats going on with the HVAC though.

Any thoughts?

Thanks
Julian

Sounds to me like your new themostat is defective, or maybe there is an air pocket/bubble in your cooling system (preventing proper flow). First, make sure coolant is full in the overflow unit (no air in the flow line). If the system is full of coolant, try installing another thermostat.

[rocky]

Did you burp the system after replacing the t'stat?

All that involves is running the car with the heater on, but with the cap off the expansion tank. This encourages any air trapped in the system get out.

Allow 20-30 mins of running and expect to see the level of coolant drop as you do this. Top up as necessary.