Help with Air Conditioning

If you, in fact, bypass the core, that is, connect the hose supplying it directly to the hose returning from it, you won't be interrupting coolant flow to anything else. The key diagram is this one (though you have to look at the others it connects to before seeing much of what's going on):



Hose 87209 is coming straight from the cylinder head (PNC 11101). The heater core is 87107A shown at the right. If you really bypass the core (connecting 87209 right to the corresponding hose on 87207A), then all you are doing is sending the same coolant to the rest of the bypass circuit one stop earlier.

The only parallel circuit that you might be starving (by making this one less restrictive) is the one from the other cylinder head outlet to the radiator. So it is possible you might reduce the engine's cooling capacity a bit. You could try to account for that by making your bypass connection go through a skinnier section of pipe, trying to match the flow resistance of the heater core.

 

What does techstream say

 

It says "Keds".

 

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if you buy OEM why need to know diameter?


Toyota Parts and Accessories - Official Online Store

 

I had this issue, the easy fix i found is to disconnect the 12V battery for a few minutes, then connecting it back, turning the A/C on and putting it on max cold, i leave it there because if i put it on hot then cold, the issue will come back.