I have an old 1999 Blazer ZR2 that came standard with 4 wheel drive.

Now i am having problems getting the 4 wheel drive to engage.

When i switch from 2 wheel drive to 4 wheel drive the switch lights up but is just flashing and the car does not engage the 4 wheel drive.

When i bought the car several years ago almost non of the electric switches worked as they are supposed to so i had to take off all of the electric switches to clean and resolder them

This includs the 4 wheel drive switch panel wich always have been working perfect after i took it apart, cleaned it and resolder several of the contact points.

Here the other day i got stuck in the snow and i just pressed on the 4 wheel drive switch but the switch was just flashing and did not engage the 4 wheel drive.

I have not yet had a look at this yet since i thought i would ask here on the forum first (And the fact that it is a lot of snow and cold out side)

I can take out the 4 wheel drive switch again to clean it and resolder if it is needed (The thing is that the 4 wheel drive switch looks to work as it is supposed to)

There might also be some problem with the TCCM i guess.

But what i think is that this is most likely a problem with a vacuum hose/hoses.

I replaced the engine PCV valve this summer and when i did that the hose broke because the hose was so brittle so i guess the vacuum hoses for the 4 wheel drive vacuum is just as brittle so that might be the problem.
Just lifting up the hose for the PCV valve was enough to break it.

Any here on the forum that have any good advice on how to fix this?


The switch panel on my car can be seen on the picture below.

The type of switch panel for the 4 wheel drive in my 1999 Blazer ZR2

 

Common issues are the TCCM and vacuum hoses.

If the TCCM clicks many times, it is going bad.

But you mentioned the rotted vacuum lines and these are vital to the engagement of the 4wd system.

There is a sticky post on the vacuum lines for the 4-button transfer case that should help with getting those operating again.

https://blazerforum.com/forum/article-submissions-discussions-47/underhood-vacuum-lines-4-button-nvg236-transfer-case-rpo-np8-107011/#post755481

 

Several easy common failure points to check before any serious diagnosis.

1. ATC fuse blown in underhood relay center.
2. Corroded connectors at TCCM (for the big red and big black wires).
3. There is a vacuum solenoid mounted on the firewall above the distributor that locks in the front axle. Check vacuum (with a gauge) to and through this solenoid.

Check and report please.

 

Thanks for the reply`s

When selecting any drivve program and pushing the switches the TCCM does not click at all.

The fact that the TCCM does not make a sound tells me that it does not get any signal/power at all.

I am pretty sure that the problem is some bad vaccum lines or corroded connectors on the TCCM as you say

I still have not opened the hood since it is cold and snowy outside but now the orads are so icy that i will have to take a look.

I will tell you what the problem is when i have figured it out

 

You'll want to check those vacuum lines since vacuum is needed to operate the HVAC system too. If it is cold out, you'll want to be able to control that!

 

christine_208. I found this page
I think this post by you will be of help

Link to your post from Oct 2017:O 3, 2017:
Under-hood vacuum hose replace - Blazer Forum - Chevy Blazer Forums

 

Strange you should mention that since my Blazer is not the warmest car i know of during winter time. I did fill after some more cooling fluid and that helped but i still do not find the car warm enough

 

That is the old one. I put an cleaned-up version in the sticky forum.

The vacuum is needed by the actuators that direct to where the air flows. Indirectly this can make it hard to warm up the inside.

 

Thanks a lot for helping me out here

When i press either 4 WD high, 4WD low or Auto 4WD the switches starts to flash but not a sound that anything will engage.

I will have to get this to work soon.
The first thing i will check is the fuses.

I will open the switch and check the soldering points since i have read that these switches are known to go bad. I have repaired this switch before so it is an easy fix.

Then i will check the vacuum lines and check that there is vacuum.


Well, i will check everything you have written down here starting with the fuses

LesMyer wrote:
1. ATC fuse blown in underhood relay center.
2. Corroded connectors at TCCM (for the big red and big black wires).
3. There is a vacuum solenoid mounted on the firewall above the distributor that locks in the front axle. Check vacuum (with a gauge) to and through this solenoid.

christine_208 wrote.
I have downloaded the updated version of the vacuum lines
Thanks for the link