Need help with understanding the heater operation. I thought I understood the system well, but...
The coolant gets warm, the heater valve when opened allows the warm water to pass through the coils of the heater core, and as air flows over the coils the warmth is transferred into the cabin.
So, fired up the car for a drive. Car was cold. Turned on heater (opened valve, and cowl vent) and within two blocks warm air came out. This even though the temperature gauge still read cold.
A couple miles later, the gauge read normal (near the middle of the dial) but only cold air blew out.
I closed the vent and turned on the fan motor, in case the outside air was too cold.
No difference.
The possibilities that come to mind are three;
The cooling system is working too well.
The heater valve is working intermittently..
The thermostat (with bypass blocked) is not allowing warm coolant to reach the heater core once the thermostat opens.
Thanks,
Rob
The most common problem with cold air from a heater is low coolant level in the radiator.
Hello Ed,
I have experienced that in other cars...
In my Hudson, I check the coolant level before every trip and it is always an inch or so above the core.
Thank you,
Rob
Rob,
Check your PMs, please.
F
Frank,
I responded to your pm.
Rob
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Frank suggested improper hose routing, and he may have hit it right on the head.
Someone posted a photo of the
correct routing a while back. I saved it and of course now I need it I can't remember where I saved it at...
The photo above is what it looks like now.
The steel tube from the water pump is connected to the top outlet on the (heater core?) right.
The hose from the head is connected to the top outlet on the (Ranco valve?) on the left.
Rob
Rob,
I don't know that flow direction through the core is terribly important, (I'm sure there's a correct way, though) but flow direction through the Ranco valve could be your culprit. I've seen them plumbed with the Valve inlet attached to the pipe that runs along the head (or hose, if it has been replaced). That tube is the return line from the heater to the pump. My thought, although only a theory, is that the heater begins to put out some heat while the bypass part of the thermostat is closed and recirculating coolant within the block, but, if hooked up backward, the coolant flow is forceful enough to re-seat the valve, causing the heat to stop.
That's my theory and I'm stickin' to it 'til someone proves me wrong.
Frank
Thank you Frank.
So, the coolant flow path is from the head to the Ranco valve, through the valve (when open) to the heater core, then out to the tube that leads back to the pump.
In my photo, the hoses, heater core outlets, and Ranco outlets are shown, but which is which?
Ranco on the left, and heater core on the right?
I wasn't able to find this info in the repair manual?
Rob
It took awhile to find but this is the correct hose routing.
Thank you Ed!
Well darn...my hoses are hooked up exactly as in the picture.
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So perhaps there is an issue with the Ranco (or whatever brand) of valve that is on there closing up after it gets warm..
I'll take the car out and get it hot and check things with the IR gun to see if the valve isn't opening.
Rob
The heater core is in the center. If you take the left hose off the ranco and put it to the bottom of the core, you should get plenty of heat all the time. If you don't, the problem is with the core or hoses etc.
Thank you Ed,
I'll give that a try.
Rob
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