4wd won't engage when warm

[Ford4223]

This was happening with my 2002 sr5 4runner it would sometimes engage the 4wd and sometimes it wouldn't. I found out it was the actuator attached to the transfer case. It was more cost effective to buy a used transfer case with a working actuator already installed than it would have been to replace just the actuator on the old transfer case.

 

[Bad Luck]

This was happening with my 2002 sr5 4runner it would sometimes engage the 4wd and sometimes it wouldn't. I found out it was the actuator attached to the transfer case. It was more cost effective to buy a used transfer case with a working actuator already installed than it would have been to replace just the actuator on the old transfer case.

You have a different transfer case. You have a vf3am transfer case which uses an actuator to change 2wd/4wd, but the OP has a vf2a transfer case which is a fully mechanical transfer case that uses a shift lever for 2wd/4wd change.

 

[4ruiner]

Thanks for the responses. The 4wd light on the dash does operate and when it is on, we are definitely in 4wd and when it is off, we are definitely in 2wd. If I read the wiring diagram correctly for this transfer case, the relay is powered and operates to switch, when the it gets a ground signal from the 4wd mechanical "detection switch" on the transfer case. Power also goes to the 4wd light on the dash, which only lights, when it gets a ground signal from the "ADD position switch" on the axle disconnect mechanism. When I get the chance, I plan to run an alternate ground wire to the relay with a switch, so that if I lose 4wd again (when I need it most, of course) I can feed the relay another source of ground to see, if that make the relay work. Sure, that's the ticket. What could go wrong?

 

[Bad Luck]

Thanks for the responses. The 4wd light on the dash does operate and when it is on, we are definitely in 4wd and when it is off, we are definitely in 2wd. If I read the wiring diagram correctly for this transfer case, the relay is powered and operates to switch, when the it gets a ground signal from the 4wd mechanical "detection switch" on the transfer case. Power also goes to the 4wd light on the dash, which only lights, when it gets a ground signal from the "ADD position switch" on the axle disconnect mechanism. When I get the chance, I plan to run an alternate ground wire to the relay with a switch, so that if I lose 4wd again (when I need it most, of course) I can feed the relay another source of ground to see, if that make the relay work. Sure, that's the ticket. What could go wrong?

I referenced my 2000 EWD and I agree with what you said. ADD position switch is for the 4wd indicator light. 4wd transfer case switch is used to ground the relay for the VSV.

I can't remember, did you remove the transfer case and add position switches and clean/check for continuity when depressed?

 

[phattyduck]

I can feed the relay another source of ground to see, if that make the relay work. Sure, that's the ticket. What could go wrong?

You should be able to hear the ADD relay click in the passenger footwell when you shift in and out of 4WD (2H <-> 4H) - that should be an easy test whenever you are having the problem. If the relay doesn't click, you have a detection switch problem on the TC. If it does click, then you have to check the VSVs, actuator and position switch for the front diff.

Your understanding of the electrical portion seems correct.

-Charlie

 

[4ruiner]

Well if anyone is waiting with baited breath, I think I have finally figured this problem out. I put a switch in the dash, that grounds the relay at the same connection, that the transfer case switch does, when 4wd is engaged. Drove for an hour or so to where I needed 4wd. The relay did not work. I flipped the switch giving the relay the correct ground and presto! 4wd. The T/C switch was no longer providing the ground as previously, but the dash switch worked, grounding the relay, triggering the VSVs correctly, engaging the ADD and that in turn showed up as a the green 4wd light on the dash. If I get really bored or ambitious, I may pull the T/C switch again. The aluminum washer under the switch is fairly thick. I may replace it with a thinner one or just grind it down to half thickness to create a more positive connection. Not feeling bored or ambitious just yet. Thanks to all for contributing their ideas. Oh, and I now have an extra T/C switch and relay.

 

[JFunky]

did you ever figure out this issue 4ruiner, because I am having this exact same problem