Bypassing heater core
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Bypassing heater core
Hey folks, I have a "new to me" 2000 Lincoln Navigator and I'm working on tracking down a problem with the AC/Heat.
Here's what I have so far:
The front ac vents do not blow or respond to any input at all
No air from Defrost, Ac, nada
The rear ac vents blow, but temperature does not change
Looking under the hood I find that the heater core has been bypassed. Using the old "cover 2 of the 3 hose ends and blow on the other" resulted in some residual coolant being blown out and now air passes through the two hoses leading into the firewall with no problem. I can clamp the 3rd hose opening and get good back pressure. Looking at the passenger side carpet, it doesn't look like any leakage has occurred.
My question is this: Why would someone bypass the heater core? And is there a way to check the operational functionality before pulling things apart?
Thanks in advance.
Here's what I have so far:
The front ac vents do not blow or respond to any input at all
No air from Defrost, Ac, nada
The rear ac vents blow, but temperature does not change
Looking under the hood I find that the heater core has been bypassed. Using the old "cover 2 of the 3 hose ends and blow on the other" resulted in some residual coolant being blown out and now air passes through the two hoses leading into the firewall with no problem. I can clamp the 3rd hose opening and get good back pressure. Looking at the passenger side carpet, it doesn't look like any leakage has occurred.
My question is this: Why would someone bypass the heater core? And is there a way to check the operational functionality before pulling things apart?
Thanks in advance.
Last edited by speedy_steve; May 14, 2014 at 01:59 PM. Reason: added additional information
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There is only one reason to bypass a heater core, and that is that it was leaking. You'll have to change the heater core (or cores) before you can get the system working again.
I'm sure the reason the rear temperature doesn't change is because the lines going back there are also disconnected.
As to the controls not working, it could be a broken vacuum line. Look around behind the battery, that's where the main HVAC vacuum line is.
Although a used car sale is usually "as is" courts have been know to make exceptions when there is something not disclosed by the seller. In most cases the seller can simply say I didn't know it was bad, you know like with worn ball joints or brakes, etc.. But with something like this, he full well knew there was no heat and why. This is something that should've been disclosed and written on the sales slip. I think you have a good case to go after him for the cost of the repairs.
I'm sure the reason the rear temperature doesn't change is because the lines going back there are also disconnected.
As to the controls not working, it could be a broken vacuum line. Look around behind the battery, that's where the main HVAC vacuum line is.
Although a used car sale is usually "as is" courts have been know to make exceptions when there is something not disclosed by the seller. In most cases the seller can simply say I didn't know it was bad, you know like with worn ball joints or brakes, etc.. But with something like this, he full well knew there was no heat and why. This is something that should've been disclosed and written on the sales slip. I think you have a good case to go after him for the cost of the repairs.
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usually one would expect a heater core that has been bypassed to have a leak.
that being said, it is also possible that the heater blend door is stuck/broken in the "heat" position, and bypassing the heater core was so that it wouldn't blow hot air all the time.
either way, you've got your work cut out for you.
on the bright side, at least you know why they were selling it now.
that being said, it is also possible that the heater blend door is stuck/broken in the "heat" position, and bypassing the heater core was so that it wouldn't blow hot air all the time.
either way, you've got your work cut out for you.
on the bright side, at least you know why they were selling it now.
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