To replace or not to replace my furnace & AC

[Soh]

Something got wrong with my furnace, and the blower (motor? fan?) of the furnace in my house keeps running, even when I turn off the furnace from the programmable thermostats. The only way I was able to stop was to turn off the switch right by the furnace.

So I called a service guy yesterday, and he did some temporary fix, but he found some other things that he didn't like, like rust and motor's noise.

It looks like it was dying, but now it's doing fine. It's about 24 years old. It'll be about $4,000 to replace the furnace and the AC. If I'm going to replace the furnace, I'll replace the AC, too. Because...
a. AC is as old as the furnace.
b. I'll get a better deal by changing both.
c. Replacing only the furnace may require taking it out to replace the AC.

I should save about $400 - $500/year. I can afford to replace it.

What do you think?

Thanks

Soh

[4 High]

If you can afford it and your going to recoup the money in less then 10 years, sure go for it.

[soko]

[ QUOTE ]
If you can afford it and your going to recoup the money in less then 10 years, sure go for it.

[/ QUOTE ]

Not only this, if he sells the house within those 10 years he's most likely going to have to have it replaced anyways all the while he is paying an extra $500 a year.

[Skoob]

Long story short, was doing a whole bunch of research lately about furnaces...

I just read that if your furnace is older than 12 years, it's not worth fixing. The new furnaces are so efficient, you will recover your investment reasonably fast, depending on where you live (climate). In colder climates, efficiency is more valuable.