Age of heating and air ?

Lennox - A/C - M/N HP25-261-1P - S/N 589M06210

Lennox - Heating - M/N CD-26-3P-TXV - S/N 5895B 61378

without knowing the manufacturer, my guess is 1989.

i assume that the ac and furnace are the same brand?

Thanks for the reply . Also what is the best resource for researching ages of HVAC units ?

The heating unit could be a 1995.

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Brent, what was the brand of the units.
If same brand, did they look like they may be the same age?

Preston’s guide is good, but I think it only goes up to 2000?

The first is December 1989. I think the serial number on the second is wrong, so I’m making an educated guess for 1989 (month unknown) or February 1995. If you can verify that serial number on the second one, I can be better.