Four-wheel drive will not engage?

JOE THE MARINE

MEMBER
2002 CHEVROLET BLAZER
4.3L
V6
4WD
AUTOMATIC
191,000 MILES

I just replaced a new AC /Delco 4wd indicator switch and a new 4wd front actuator switch and replaced all the vacuum lines and new vacuum line check value because there was tranny old in them with silicone lines, when I hit the 4whH button, I don't feel or hear anything engaging, is it possible that the transfer case shift motor actuator is causing the problem? I'm all out of ideas on these issues and driving me crazy. If you have any diagrams or printouts on what the problem could be, it really will help. Thanks for any help on this issue. God bless you on the work you do. I even checked on YouTube, but too much confusing about what and how it could be so far.

6 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,602 POSTS

Hi Joe,

Yep, we just fixed this problem in a car in the shop, it was the ATC fuse if you can believe it, but you should check the other 3 that run the system as well which are shown in the diagrams as well. Here is a guide to help you check the fuse and the 4wd wiring diagrams so you can see how the system works and I have included the fuse location as well.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the images (below). Please upload pictures or videos of the problem so we can see what's going on.

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Sunday, January 14th, 2024 AT 12:10 PM

JOE THE MARINE

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86 POSTS

I did what you said, but prior to this I checked all the vacuum lines and one was crossed, didn't how that happen. Also, now my heat inside is all screwed up! I get heat through my top vents (75 %) and floor heat is the other 25 %. Could this be another problem? Also, the defroster heat blower is only getting very little heat. I looked inside the glove box and saw an actuator there and when I switched the controls, nothing happened. I pulled the vacuum line off and no vacuum came out. Is this another problem? Seems like I fix one thing and other starts, crazy. Thanks for the help with the last question, it helped.

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Tuesday, January 16th, 2024 AT 8:44 AM

KEN L

MASTER CERTIFIED MECHANIC
47,602 POSTS

Which vacuum lines do you speak of? I don't see any that works the 4wd system. Check out the images (below). Can you upload images of what you are talking about?

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Tuesday, January 16th, 2024 AT 9:28 AM

JOE THE MARINE

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86 POSTS

The images are not on my Chevrolet Blazer, the one I installed are call Ac Delco 4wd indicator lamp switch, which has 4 vacuum lines coming out the top of the transfer case. And one line connects to the 4wd front differential vacuum, which is located under the battery tray, which connects to the cable, which were a pain to do and get too. My concern was since I replace the switch and all the vacuum lines, did this have any effect on the heat inside?Or is it some kind of HVAC actuator (s) inside? Oh, thanks for the feedback so far.

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Tuesday, January 16th, 2024 AT 2:10 PM

JOE THE MARINE