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2004 Mitsubishi Eclipse Spyder

When I drive in ambient temps below 40 and turn on the heater my car makes a screeching, belt like noise and then the power steering malfunctions veering me to the right. When I turn off the heater it immediately self corrects. My mechanic says the alternator and the belts check out. Please help!!

Is the screeching coming from under the hood? It sounds like a belt is slipping. The power steering pump and AC are both on the same belt. This has a automatic compressor controller. When AC is selected it puts extra load on the belt. Plus power steering seems to make the most noise when cold. If either is causing the belt to slip, you will lose power steering assist. Unplug the AC compressor. It’s a little plug with 2 with wires that plugs in to the compressor. If this fixes your problem, it gives you a place to start. I attached 2 pics for you.

It’s amazing to me how many failure modes are possible in cars these days. Turning on the passenger compartment heat causes the car to veer to the right?

I concur with the post above, this is probably related to the AC compressor. When you turn on the heat, somehow the AC compressor must kick on briefly too. You might try experimenting using different modes when you turn on the heat. For example, try just the floor heat, but no defrost. Sometimes defrost will turn on the AC, not to cool the air, but as a dehumidifier.