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My 4wd quite working on my 1998 Chevy Blazer - the 3 push…

My 4wd quite working on...
My 4wd quite working on my 1998 Chevy Blazer - the 3 push buttons 2WD 4HI 4LO are not lite up. I have removed the battey and the battery tray and found the vacum pump. The cable that the diaphram actuator seems to move freely when I push pull with my fingers. With the engine running, the 3 buttons don't actuate the the diaphram and pull push the cable (nothing). I disconnected the vacum hose from the diaphram actuator and could not detect any suction at the end of the line with engine running. What should I look at next?
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Answered in 2 hours by:
1/18/2018
Todd Audette
Todd Audette, A.S.E Certified Master Technician
Category: Transmissions
Satisfied Customers: 427
Experience: GM Transmission Technician
Verified

Hi my name is*****'m an A.S.E Certified Master Technician with 30 + yrs GM experience. I'm reviewing you question and would be happy to assist you.

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Please give me a little time to review and i will be back to you shortly

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If the lights on the switch aren't lighting up it may not have anything to do with the cable or the vacuum actuator it has more to do with the 4wd module.

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Customer reply replied 6 months ago
OK - I will do some more checking - might show something on diagnostics?
Customer reply replied 6 months ago
Or could it be a fuse? I am leaving now and will check in tomorrow - Thanks

Ok check fuses tomorrow and get back to me. I will tell you what to do next

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Customer reply replied 6 months ago
I don't see any burned fuses.

Behind the right side kick panel on the passenger side just forward of the door is where the module is located. Un plug it and check for any corroded wires...plug it back in and see if it starts to work

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Customer reply replied 6 months ago
OK -thanks for the diagram. I opened the panel - pulled the harness plug, No corrosion. plugged back in snug, started the vehicle. - No ***** *****ghts behind the 3 2/4 wd buttons. Could the module be bad?

Yes but i'll have you check 1 more thing first...Stand by

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Customer reply replied 6 months ago
OK

Was there only 1 plug on it

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Customer reply replied 6 months ago
1 BLUE PLUG
Customer reply replied 6 months ago
Just plugged in OBD tool - no error codes came up

Test for power on the orange wire

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Customer reply replied 6 months ago
OK will do

Make sure to test with the key in the on position

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Customer reply replied 6 months ago
I pulled the blue plug out, found the largest orange wire checked the female part of the blue plug, no power, checked the back side of the wire crimp inside the plug and poked through the wire insulation with a "light up tester" with the alligator clip grounded - no power. Ignition key was on and headlights were on - engine not running.
Customer reply replied 6 months ago
Was the plug supposed to be plugged into the module?

No I didn't need to be plugged in....How many wires on that connector?

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Customer reply replied 6 months ago
one moment -
Customer reply replied 6 months ago
25 wires
Customer reply replied 6 months ago
There were several orange wires - I tested the largest one

Check the ATC fuse at the underhood fuse box with a test light. Also check the 4wd fuse at the instrument panel fuse box with a test light....test both sides of the fuses with the key on

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Customer reply replied 6 months ago
ok - one moment
Customer reply replied 6 months ago
OK WITH KEY ON - ATC fuse terminals under hood fuse box = no power either side, 4WD fuse at location #15 on the instrument fuse panel per owners manual - no power on either terminal -both fuses appear to be OK and not burned

Give me a little while to investigate why you have no power to these fuses and I will get back to you

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Customer reply replied 6 months ago
OK thank you - in the meantime, I will look for loose connections that I can locate.

Yes do that

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Are you sure you had a good ground connection on the clip end of the test light

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Customer reply replied 6 months ago
I will double check with various ground locations unpainted
Clamp it to the negatve terminal on the battery that is the best spot. Verify your test light works by touching the positive side with the point end
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Customer reply replied 6 months ago
Yep - I use a long alligator clipped wire and extended the ground connection to the negative battery terminal and this time I get power at both the ATC fuse terminal and the 4wd terminal at the instrument panel. But still no power at the termination of the orange wire on the plug to the 4wd module inside the kick panel on the passenger side
Customer reply replied 6 months ago
Sorry for the mis fire
Customer reply replied 6 months ago
You were correct, I did not have a good ground
Customer reply replied 6 months ago
Question - when I tested the orange wire - the plug is unplugged from the 4wd module - does it need to be plugged in for that test?

No it does not have to be plugged in

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You said there were several orange wires....check all of them

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Customer reply replied 6 months ago
OK - will do
Customer reply replied 6 months ago
The big wire I first checked and called the "orange wire" is actually a large RED wire with no power
Their are 4 other orange wires - 2 medium size orange wires at the opposite end of the block ( side by side) and both have power. Then 2 very small orange wires in the mid section of the block and no power on those two
Customer reply replied 6 months ago
I guess I am a bit color blind - sorry for that
Customer reply replied 6 months ago
NAPA has a replacement module, 32 pin that looks like the right part, if that is what is needed. It will take me about and hour to go and get https://www.napaonline.com/en/p/NDP5980000
i think that is what needs to be replaced. Keep in my that rating this service will not close out the session and i will be available for further diagnosis and follow up questions you may have for me
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Customer reply replied 6 months ago
OK - I am on it. I will put it in and let you know. So far you have been helpful and have earned a tip. Will send you a note later today when I get it done. Thanks
Ok sounds good
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Customer reply replied 6 months ago
Hi Todd - I put the new 4wd module in and the ***** *****ghts don't light up at the 3 4wd buttons and don't actuate. I still have the vacum hose disconnected from the diaphram actuator and don't feel any suction at that end of the hose. What should I look at next?

Sorry to here that....based on our conversation i was thinking that may have been it..keep in mind that i'm not there testing things myself so this can be challenging to say the least. You wont have vacuum there until the transfer case has completed a shift in to 4hi or 4lo....I recommend you test every fuse in the truck with the test light....Key on. There is a vacuum switch on the top of the transfer case that supplies the vacuum to that actuator....That actuator engages the front axle but not the transfer case.

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Customer reply replied 6 months ago
OK - I understand - I will keep working on it. Thanks
Customer reply replied 6 months ago
Yep - I understand - I am going to check the vacum switch tomorrow. I have to pull off a protector plate to be able to get to it, but no big deal. I will check back with you later. I will try and see if it is in 4wd or not and see if the encoder motor is doing anything. I am sure you could fix it faster than me - I just wanted to give it a try. I can take it in to a mechanic - not an issue, just wanted to try my luck first.

Have you made any progress?

Todd Audette
Todd Audette, A.S.E Certified Master Technician
Category: Transmissions
Satisfied Customers: 427
Experience: GM Transmission Technician
Verified
Todd Audette and 87 other Transmissions Specialists are ready to help you
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Customer reply replied 6 months ago
I replaced the module, transfer case switch, transfer case motor and push buttons on the dash and now it works. Thank you.

Great news. Glad to hear you got it fixed

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