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AC relay Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Fri, 27 Jul 2007 08:34:29 In Reply to: a/c cuts out after 5min., rich, Fri, 27 Jul 2007 08:11:55 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Most likely the AC relay. If the AC isn't blowing cold, open the hood and look at the AC compressor. Is the clutch pulling in? When the clutch is out, the outer pulley rotates with the belt, but the inner part is stationary. When it pulls, in, the inner part rotates with the outer.
The system shutting down can be due to a few reasons. One would be low refrigerant pressure. Or the freeze-up switch is detecting the condensor freezing. But that would usually clear up after a bit.
Most likely is is a set of poor contacts inside the AC relay. The contacts build up carbon over time, and that creates a resistance. When you first start the car, enough current can go through the resistance to engage the clutch. But that current through the resistance creates heat. The hotter the carbon, the greater the resistance. So the next time the system cycles on, it won't pass enough current to allow the compressor clutch to pull in. But the contacts stay closed, so enough current flows the keep the contacts hot.
Pull the AC relay. Spray the socket with some contact cleaner. While that dries, pop off the plastic case. Inspect the relay contacts inside. They're probably looking a bit burned. Clean them up by LIGHTLY scraping them with an emery board or some fine sandpaper. You're not trying to wear them down - there is a thin plating on them you don't want to wear through. Just knock off the black stuff and get down to shiny. Give the prongs on the bottom of the relay a quick buff with the sandpaper. Put it all together, and you'll probably be just fine (and cool).
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