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For well over a year, my 1994 Suburban has been making a strange sound. It seems to be getting worse, so I have decided to solicit help. A little difficult to describe, but when I start the engine, and especially when I turn the engine off, there is a loud clicking (best term I can think of) sound that comes from under the dash on the passenger side. I have never timed it, but the clicking can last for about 10 seconds when you start the engine and at least 30 seconds when you turn off the engine. I am thinking it is somehow related to a vacuum of some sort that keeps opening and closing a valve of some sort. Has anyone experienced this situation before and if yes how do I solve it without spending an arm and a leg?
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First thing I'd check if I owned the unit would be the heater / air conditioner fan. Especially so if the clicking has a regular "cadence" to it.
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It doesn't sound like a fan. It sounds like something is repeatedly opening and closing.
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From your description, it sounds like a noisy blend or mode door motor for the Heater/AC unit. The plastic gears start to strip out and make a ticking/clicking noise, although they can sometimes still function.
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Fishkillr was able to diagnose it for me. It is the door that determines whether outside or inside air is used. Apparently, the gears are somewhat stripped and that causes the door to continuously snap open and closed whenever I turn on or turn off the ignition switch. I will likely just live with it.
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