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Windshield fog

I have a 1997 Honda Odyssey and the windshield defogger no longer works. The AC works, the heat works, the fan works, bu I have to drive with a rag in my hand to wipe off the windshield every few minutes. Any ideas?

So you can’t manually select ‘a/c on’ when the system’s set to ‘defrost’? Whatever switch normally turns on the a/c compressor when you select defrost must not be working.

Is the problem that you can’t get the air to come out of the defroster vents at the base of the windshield?

If air comes out the defroster slots, you may have a bad heater core that is allowing boiling coolant to escape and condense on the windshield.

I can select a/con and it goeson, but it does not unfog the window

air comes out but the window stays fogged except for a tiny bit at the bottom. it used to unfog the entire window almost instantly

Is your recycle air switch on? Do you feel air blowing out the defroster vent?

air comes out but the window stays fogged except for a tiny bit at the bottom. it used to unfog the entire window almost instantly.

that sounds possible, but the heater does work. or is that something different?

Yes, it works, but it is also probably leaking. The moisture from the leak is getting absorbed into the air before it hits the windshield, preventing the air from absorbing the additional moisture on the windshield, leaving it fogged up.

I’ve tried both the recycle air and the outside air and neither unfog the window. Air does come out, but with no effect.

so what do I do about this? this is an old car with many miles on it.

A part of the defogging process is kicking on the ac to dry out the air before it gets to the windshield. Many cars have worked without ac to do that, are you experiencing any coolant loss? Does the AC work in this car? It may be as simple as cleaning the inside glass.

the AC works fine so I don’t think it is that.someone else suggested a bad heater core leaking moisture into the air. this sounds likely to me.

there is steam coming out of the heat vents that I notice sometime so this seems very likely. is that soemthing that can be fixed or does it need to be replaced? I don’t want to put alot of money into this car as it is pretty old.

Confirm the leak and replace the heater core.

You could remove and cap the lines to the heater core under the hood. The lines from the engine, just loop them together. You won’t have a heater, but the windshield will clear.

ok thank you for the advice. I’ve been trying to figure this out for a long time!

Are you experiencing any coolant loss? if not a blow out of the ac drip tube could be the solution.

i do find a bit of coolant on my driveway but could not find where it was coming from.