Alternator and gas mileage

[masonm]

My sweet little '92 Paseo used to get 28-30 mpg in the city. Now that I have my new alternator, I am getting 17-19 in the city. The only other variable is that it has been really hot in southern Caifornia since I changed the alternator and I have used the a/c quite a bit. However, I have never heard of a/c taking mpg down 10 miles. Is it possible that there is a problem with my new alternator?

Also, since I had the new alternator installed, when the a/c is on and I am going 45mph or higher...after I quickly slow down and put in the clutch to make a turn, the engine dies. It only does this sometimes.

Any comments on either problem?

[Tercel GTS]

Did you install the alternator?
Look at the fuel pressure regulator at the end of the fuel rail above the alternator and see if the vacuum hose got knocked off/torn.

[toyomoho]

That a pretty good drop in mileage. The A/C will drop you mileage a few MPG, the alternator much less.

[Donald]

From my experience, the A/C can make quite a difference to your milage if you are making several short trips, in traffic especially.
That big sheet of glass in your rear hatch acts as a solar panel heating the interior of your car and making it into an oven. Try tinting your windows.

What color is your car?

I got an appreciation of the difference that things like color and glass area have on the interior of a car by comparing my Camry wagon - (dark slate gray), and my wifes Camry sedan - (metalic silver), same interior color in both. Her car was always cooler than mine parked side by side in the sun. Tinting my windows made a difference but her car was always still cooler.

Try running your A/C at a slower fan speed, and using a slightly warmer than full cold, setting on the tempreature slider after the car cools down a bit inside. That will make the compressor cycle off more frequently and save gas. Select the recirculating mode and open only the dashboard vents.

JC Whitney used to sell an adjustable vacuum switch that you could install into the compressor circuit, and connect to your intake manifold, it would cut the compressor out when you accellerate and turn it back on when you cruise. This really helps with smaller cars that don't have a lot of surplus power, it saves gas and allows you to still have your normal accelleration with the A/C on. I don't see it in their catalog anymore, but somebody else might sell one.