During the past few weeks I have been noticing a few "quirks" with my climate control. I only drive 6 miles to the office so not really needing heat during the summer but, I have noticed that as I increase the temp the fan increases but only cold air comes out.


This morning I decided to run a few tests.

Making sure the engine is up to normal operating temperature, the needle is in the middle of the gauge;

Turn A/C off, heat up to HI, engine at 1200RPM, blows COLD air,
A/C off, Heat HI, engine at 1900RPM blows HOT air,
A/C off, Heat HI, engine at 1300RPM Blows COOL air.

Seems I need my RPM to be around 2000 before I get warm/hot air. Can anyone add to this?

Mark

 

Diver, it sounds like your flow control valve for the engine coolant is not strong enough to open at low RPM. When the engine RPMs come up, the coolant system flow increases, placing more pressure on the flow control valves. I am not sure what else could cause something like you are seeing. There are no vacuum lines that I can see controlling the system.

 

Thanks for the info Chris. New data to add.
After further testing today I determined that;
At stop, engine normal operating temp (needle midway on gauge).
Temp set to HI with engine on idle, warm/hot air, fans blowing fast.
Temp set to 85, engine on idle, cool air, fans blowing fast.
Temp set to 85, engine 2000 RPM, cool air, fans blowing fast.
Drivers temp set to 85, passenger set to 65, hardley any air, fans not blowing or just barely.
Drivers temp set to 65, passenger set to 85, hardley any air, fans not blowing or just barely.


The plot thickens

Thanks for input people. Perfect time to fix this as it is still nice and warm out there


Mark

 

No, incorrect!! You need to change your Aux coolant pump. It's located under the heater control valve on the right side of the radiator.
Great job listing the symptoms!! That really narrowed down the problem very quickly. I also recommend changing the thermostat and coolant when you replace the pump.

You could have another problem but fix the pump first and see how it acts. The heater control valve could be involved with this also. So check that both items are receiving power before replacing. Just in case it’s a wiring problem or a fuse.
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