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Hey everyone, I started up my truck (02 7.3l lariat) last night and had left the blower selector on the defrost/floor selection. When I turned the **** to select any other selection, it remains stuck on the defrost/floor selection. The air /heat controls still change the temp, the a/c works, and I can turn the system off. But when I turn it on, it's stuck on the defrost/floor selection. I pulled out both fuses that control the blower motor and the EATC blower relay, and they were both good. Wiggled the wires attached to everything and didn't notice any difference. Anybody have any suggestions?
The vacuum pump is on the passenger side fender. It should run whenever the engine runs. A vacuum tester like Mighty Vac can help to decide whether there is a leak or if the pump is bad. One way to isolate is to use a golf tee to plug the lines that you want to isolate. The most likely leak location is inside the fenders-the vacuum line that runs to the hubs is minimal quality.
That said, the more likely problem is a bad pump. The hub tubing only has vacuum pulses when you first select 4WD. The pump is easily checked for operation.
Larry
vacuum lines control the heat/air control unit for the ventilation system?
Yes, vacuum is used to switch the mechanism around and is designed to default to defrost when it fails. You can pull the line off of your pump and hold your finger over it while the key is on and engine is off. If the pump is working it will build vacuum and stop almost immediately with your finger on the inlet.
Sorry for the initial disbelief! I was thinking electrical the whole time. So my truck is a 4x4. I have the haynes manual. Is this the only vacuum pump for the whole truck? I will test it this afternoon using the key on, engine off method. Is replacement fairly straight forward?
Sorry for the initial disbelief! I was thinking electrical the whole time. So my truck is a 4x4. I have the haynes manual. Is this the only vacuum pump for the whole truck? I will test it this afternoon using the key on, engine off method. Is replacement fairly straight forward?
That is the only vacuum pump. If there is a leak it should run continuously when you turn the key on, it's 12V. If it doesn't run at all when you pull the hose off of the intlet then the pump is not working. Replacement looks to be pretty straight forward but I haven't had to do it yet.
Thats why I asked 4X4 and was wondering if it was working, unless its a manual style setup then no vacuum lines to the hubs. The only use for vacuum on these diesels is 4X4 and heater controls.
So my vacuum pump is working. Could it be the vacuum solenoid?
But, is it constantly running? If it is, there is there is a leak. These rubber hoses are getting past 12 years old, and the ones going into your hubs are the first ones to start cracking and breaking down. I'd check those hoses first.
Actually it is constantly running. When I operate the 4x4 with the engine off, I can hear a click on both sides. I don't know if that means the 4x4 is engaging. I checked the lines running to the hubs, and they look intact. Barring a little hole that I can't see, that doesn't seem to be the problem.
There is a line off the solenoid that is broken. It goes over and down behind the reservoir located in front of the pump. Incidentally it has been broken since I owned the truck. (See Pic)
I pulled the line apart that comes off the solenoid and goes behind the firewall and I hear a hissing noise. That line I'm assuming runs the heater control. I think I should fix that broken line anyway, but any more troubleshooting thoughts?
I also just pulled the line off the pump that goes to the reservoir next to the pump. When I plug the hole with my finger, the pump stops. I couldn't really see what lines come out of the reservoir. That line above in the photo I posted goes to my hubs. That explains why I have to manually lock the 4x4 hubs to have the switch turn it on. That's been going on for the three years I've owned it. So I must have a leak somewhere else in the system?
