johnnyflames

Hello Everyone,
Today, while starting off for a drive, my 71 Cutlass convertible's windshield fogged up to the extreme. The top was up and when I tried to run the defroster, the windshield only fogged up more.
Has anyone had the same issue?
The fan blows more than enough on the interior windshield, so that isn't it.

Thanks,
John

texxas

Leaky heater core. Check under the passenger floor mat for moisture.

Tedd Thompson

Your heater core has taken a dump.. A quick check can be done by bypassing the heater by attaching the heater hose to itself thus bypassing the core. Your windshield should now not fog up but you will not have a heater.... Tedd

Partagas

Assuming you have a non a/c car, and if it was cool and humid there overnight as it was here in MN this morning, it's normal. The cold glass lags behind air temp as it warms up in the morning, causing the moisture in the warmer air to condense on the cooler glass. Then, when you turn on the defroster (without the drying benefit of a/c), you bring fresh humid air into contact with the cold glass resulting in more condensation/fog. It takes warm defroster air to clear a foggy windshield so your engine would have to warm up first. With a/c, the process is quicker as the moisture condenses on the cold a/c evaporator coil before being blown onto your windshield where the drier air actually "pulls" the condensation off your windshield then.
If, however, the fog on your windshield persists and feels greasy, and/or if you notice the "maple extract" smell of antifreeze when you turn on the defroster, then you may have a leaking heater core. My bet is that this is just normal fogging on a cool fall morning.

johnnyflames

Thanks for all the advice.
This morning in Michigan, it was cooler than normal.
I'm gonna try the heater hose tip anyways.

John

Tedd Thompson

As mentioned above you usually can smell the antifreeze if it is leaking or the floor will be wet under the core.Only takes a few minutes to bypass the heater though.... Tedd