Thursday, November 09, 2006

1994 Ford Ranger Engine surges when AC defogger is tuned on: No Codes


My engine runs OK as long as I don't use the front dash defogger. If I set the AC button to floor setting, again engine runs fine. I scanned for codes and there is none. Can you give your insights on this problem?

ATS Advisor:

When you set your AC button to the defogger mode (see picture), the AC is actually activated and is controlled by Freon pressure which is monitored by your AC computer. When this happens, the AC computer signals the engine computer to raise the rpm to prevent the engine from stalling. However, if Freon pressure is low, the AC clutch is de-activated which cause the AC system to stop and rpm goes down. With these two modes, it will create a high or low rpm or surging condition. Try testing your Freon level and top it up with freon if possible.

ATS Tip:

Putting your AC setting to the floor mode de-activates the AC system causing your engine to run normal because the AC computer is not controlling the engine rpm anymore. ATS can supply you the Freon pressure specs for this vehicle.


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