Ported Vacuum Switch Temp Rating?
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Ported Vacuum Switch Temp Rating?
Can someone tell me the temperature rating for the ported vacuum switch that controls the canister purge valve (EVAP system)? This is for a 1979 Ford F-250.
NAPA lists about 3 different switches, and I don't know what temperature rating I need for this system to work properly. Mine broke off and I don't see any markings on it. The local Ford dealership is no help at all. The man behind the counter didn't even know what I was talking about!
NAPA lists about 3 different switches, and I don't know what temperature rating I need for this system to work properly. Mine broke off and I don't see any markings on it. The local Ford dealership is no help at all. The man behind the counter didn't even know what I was talking about!
Post Fiend
Joined: Apr 2008
Posts: 8,261
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From: Big Sky Country
Asking for just about anything pre 1980's at a dealership these days will get you that "blank stare" look.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
That ported vacuum switch also goes to the EGR system. Once the engine coolant temperature passes the rating, the EGR system is in use. The colder the switch is rated for, the less NOx emissions the vehicle has, however there is a greater risk for driveability issues. The hotter the switch is rated for, the driveability is strengthened, but NOx emissions are increased. If this vehicle doesn't need to pass a smog test, choose a "warmer" switch. Usually a rating around the thermostat temperature is a good ballpark. If you can find one between 180 and 195, it's a safe choice. Check that your new switch has the same number of ports as your old switch.
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