Help Needed: Vacuum Troubleshooting
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Help Needed: Vacuum Troubleshooting
I have an 05 F250CCLBDiesel4x4, and had a cracked vacuum line at Right-Front auto-lock hub, which was taped over and things were OK for quite some time, until this morning.
Very cold here last night, ran the truck last night with full heater functionality, parked it in a snowbank with the steering at full-lock left.
This morning, started it up, pulled outuva the snowbank, turned hubs from Manual to Auto (Auto function hasn't been operative for a while), and noticed that the HVAC was only blowing out of the Defrost vents.
Having read through here about vacuum, I figured that it was that cracked line at the right hub that is now leaking. However, I went out at lunch, pulled the line off the hub, put a screw in it and zip-tied it, but still the same thing: HVAC air only through the defrost vent, regardless of switch position. Turned engine off, then turned ignition back on, vacuum pump runs continuously.
Might someone direct me to any documentation re. vacuum system component location and hose routing, to assist in the diagnosis?
Thanks in advance, Mark
Very cold here last night, ran the truck last night with full heater functionality, parked it in a snowbank with the steering at full-lock left.
This morning, started it up, pulled outuva the snowbank, turned hubs from Manual to Auto (Auto function hasn't been operative for a while), and noticed that the HVAC was only blowing out of the Defrost vents.
Having read through here about vacuum, I figured that it was that cracked line at the right hub that is now leaking. However, I went out at lunch, pulled the line off the hub, put a screw in it and zip-tied it, but still the same thing: HVAC air only through the defrost vent, regardless of switch position. Turned engine off, then turned ignition back on, vacuum pump runs continuously.
Might someone direct me to any documentation re. vacuum system component location and hose routing, to assist in the diagnosis?
Thanks in advance, Mark
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Vacuum pump seems to run continuously, HVAC blows from only defrost vents (big leak or non-functional v pump). Sitting at a traffic light, for the heckuv it, I threw the 4WD switch momentarily to 4Hi, then back to 2Hi, and air came out the floor vents! For about 45 seconds, then it reverted back to defrost only.
Sitting in the driveway, I tried this several times, varying the 4WD switch (2 to 4, hold at 4, 4 to 2) and in each change of the 4WD switch, it takes about 15 seconds and then the air follows the dash switch position and continues in that "properly functioning" mode for about 45 seconds and then it reverts to defrost only. I also checked the vacuum pump and during these momentary "properly functioning mode", the pump continues to run.
I'm stumped, looking for help.
Please?
Mark
Sitting in the driveway, I tried this several times, varying the 4WD switch (2 to 4, hold at 4, 4 to 2) and in each change of the 4WD switch, it takes about 15 seconds and then the air follows the dash switch position and continues in that "properly functioning" mode for about 45 seconds and then it reverts to defrost only. I also checked the vacuum pump and during these momentary "properly functioning mode", the pump continues to run.
I'm stumped, looking for help.
Please?
Mark
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Joined: Jan 2011
Posts: 18,849
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From: Puget Sound
That Doesn't Suck
I don't know about the '05, but my '00 has a device on the passenger-side fender with a two-vacuum hose connector and a three-wire connector. It's about the size of a normal computer mouse and this is the shift-on-the-fly 4X4 control module. The cap on mine was leaking and I ended up with just defrost and the auto transmission shifted up earlier than normal (35 instead of 42MPH). If you want to verify, pull the vac line and plug the holes. If you get heater... go to Ford and hand them about $60 and they will give you a shiny new module.
I could be wrong, but I think the only time you have vac to the hubs is when you engage the 4X4: Only defrost AFTER you switch to 4X4... bad line to the hub. Only defrost BEFORE you switch to 4X4... bad module (or other vac leak under the hood)
I could be wrong, but I think the only time you have vac to the hubs is when you engage the 4X4: Only defrost AFTER you switch to 4X4... bad line to the hub. Only defrost BEFORE you switch to 4X4... bad module (or other vac leak under the hood)
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