2001 Esof
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Mountain Pass
Joined: Jun 2004
Posts: 133
Likes: 14
From: Massachusetts
2001 Esof
2001 SD. First real snow of the season this weekend, and it will not shift into 4WD when the hubs are set to "auto". The light on the dash indicates it is in 4WD but it is not. As soon as I turn the hubs to "lock" I am all set. I had the ball joints replaced a couple of month ago, and this is the first time since then that I have needed 4WD. It was working fine prior to that. Any thoughts.
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Mountain Pass
Joined: Jun 2004
Posts: 133
Likes: 14
From: Massachusetts
Another thing is I noticed a couple of days ago that I have no back-up lights. Fuse number 28 (15A) under the dash indicates it controlls the ESOF hub lock solenoid, vacuum pump motor, backup lamps, and a couple of other things. However the fuse is fine.
Also the manual also indicates that in the engine compartment there are 2 relays (#40 & 41), which are the ESOF relays #1 & 2 (although I do not think these are the problem). However there is no indication where they are.
I will check the backup lamps to see if the are blown (however I do not think they are). Sounds as if its an electric problem. Any ideas?
Also the manual also indicates that in the engine compartment there are 2 relays (#40 & 41), which are the ESOF relays #1 & 2 (although I do not think these are the problem). However there is no indication where they are.
I will check the backup lamps to see if the are blown (however I do not think they are). Sounds as if its an electric problem. Any ideas?
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Mountain Pass
Joined: Jun 2004
Posts: 133
Likes: 14
From: Massachusetts
I checked the vaccum at each hub with a gauge. I plugged one side and tested the other, than swapped it around. Each side is pulling about 1.5 inches of vacuum. Is that all the hubs need? It appears to me that it is not a leak. I also took the hubs off, and checked each side. They looked ok, so I wiped the "o" rings with a clean rag and re-installed. I did not have time to test drive. I guess I am asking is if the 1.5 inches of vacuum is all that is needed to engage the hub when set to auto. That way I can move on to the next step if that vaccum is ok.
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Mountain Pass
Joined: Jun 2004
Posts: 133
Likes: 14
From: Massachusetts
Finally had time to check it out yesterday. Needed a new PHV soslenoid. Put it in today and the system works fine.
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Scott, what Chris was saying is if you have the selector on floor heat, and it only come out of the defrost, you have a vacuum leak.
The vacuum is used to lock and unlock the hubs, just a time bump of vacuum will do it.
Your blend door, the flap that throws air to the floor or defrost, is also vacuum operated.
In a system operating correctly, vacuum will hold the door open to allow floor heat. If no vacuum, door closes and you only get defrost, no matter where you set it to.
Keep this in mind for the future, glad you have discovered your problem.
The vacuum is used to lock and unlock the hubs, just a time bump of vacuum will do it.
Your blend door, the flap that throws air to the floor or defrost, is also vacuum operated.
In a system operating correctly, vacuum will hold the door open to allow floor heat. If no vacuum, door closes and you only get defrost, no matter where you set it to.
Keep this in mind for the future, glad you have discovered your problem.
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