finally on long island we get a significant amount of snow that eventually got coated under 3 inches of ice. and yet two days later its still not melting and everything is slippery. especially when ur 4 wheel decides not to work.

well heres what i know so far, i have the electric shift transfer case. the drive shaft engages, you can hear the encoder motor engaging and the shaft will not turn by hand. so the transfer case is defintely engaged. i also hear a clicking noise behind or under my glove box when i push the button.

so i figure move on to the next step which would be the vacuum actuator. i now can plainly see that the actuator is not pulling the cable to engage the front diff. so i pull off the vacuum line and to me it seems like i a getting very little vacuum, almost nothing at all. i traced all the lines to the tranny and back to the vacuum ball/ and all other lines also connected. i replaced 75% of these lines during the summer and just recently fixed any that might have been a little cracked and worn. yet still no vacuum to the actuator.

i am gonna check for a vacuum on some other lines that share themselves with the 4wd lines to see if i am getting a vacuum to them.

if i have no vacuum(which would be weird, cause the truck runs great for a 92 with 167,000) then where would i begin to rectify the problem. and could the actuators diaphragm be worn enough that its not creating a vacuum.

hopefully its just the actuator and nothing else. thats easy to do. but i could use some advice cause this ice is gonna kill me, plus i gotta do my rear brakes so the 4wheel will actually help me stop better on the ice

 

I would check the vacuum switch on the drivers side of the transfer case. This switch fails constantly and GM has a TSB on it, they have a redesigned switch. It is in the supply chain now and it also fixes a problem with the heater controls not working because the switch seal fails allowing fluid from the transfer case to be sucked up into the vacuum lines....

 

thats kinda of what i was leaning towards, but so far all i can find onlineis a three prong switch, and i got only two lines into the switch. so im gonna continue shopping till i find a prt number and general price.

you wouldnt have the part number or the tsb on this would ya?

 

I don't know about the switch, but I had a bad vacuum actuator last winter. It was a dealer only part and ran around $85.

 

Here's the buletin that he's speaking of, but it does NOT apply to your truck it's only listed for 2001-2003 model years. I have only experienced this specific problem with 2003 MY trucks myself. Anyway, you should have a 3 prong switch, they didn't build one (not to my knowlege) with a 2-prong. There should be a vacuum supply(from the engine), switched vacuum (to the front axle servo) and a vent. If your's only has 2 prongs...you need to fix that first and recheck.






" name=forward>
Document ID# 1350749
2003 Chevrolet Blazer - 4WD


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Subject:
HVAC Mode Switch Inoperative or Stuck in Vent Mode, Oil in HVAC Control Head and/or Vacuum Lines (Replace Transfer Case Vacuum Switch and Contaminated HVAC Components) #03-01-38-009 - (06/25/2003)[/align]
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Models:
2001-2003 Chevrolet Blazer, S10[/align][align=left]




2001-2003 GMC Sonoma[/align][align=left]




2001 GMC Envoy, Jimmy[/align][align=left]




2001-2003 GMC Jimmy (Export Canada Only)[/align][align=left]




with 4WD and Two-Speed Electric Shift Transfer Case (RPO NP1)[/align]


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Condition
Some customers may comment that the HVAC mode switch may be inoperative or stuck in the vent mode. After some diagnosis, oil in the HVAC control head and/or vacuum lines may be found.
Cause
When the transmission or transfer case heat up, the oil may expand and find its way into the transfer case vacuum switch. This oil expulsion may cause the vacuum switch seal to fail and allow transfer case oil to be drawn into the HVAC vacuum lines.
Correction
Replace the transfer case vacuum switch. Refer to the Transfer Case Vacuum Switch Replacement procedure in the Transfer Case sub-section of the Service Manual. Also, replace all contaminated parts in the HVAC system.
Parts Information





Part Number

Description


15664811

Switch -Transfer Case Vacuum
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use:





Labor Operation

Description

Labor Time


K4120

Switch, Vacuum Control Transfer Case - Replace

0.6hr


Add

Diagnosis Time

0-0.3hr


Add

With Skid Plate

0.2hr


Any additional time for replacement of HVAC components must be submitted as Other Labor Hours and requires appropriate authorization.





GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.


WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

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" name=forward>
Document ID# 1350749
2003 Chevrolet Blazer - 4WD

 

I'm afraid only studded tires will help you stop better on ice. You might stop marginally better with Blizzaks or Green Diamond tires, but beyond that only studs help.

Check like nuts for vacuum leaks. Are you getting a 4wd light? If not, no vacuum is reaching the actuator; if so, adjust the cable on the actuator as it's not adjusted properly, preventing the axle fron engaging.

 

yes it is a three prong , which i could get. and im not flying around in icy conditions, plus my tires are brand new and never give me a problem. my rear brakes are shot and was only looking for a little assistance in controling the sliding stops. im not a moron, believe me i have strategicly steered my blazer into snow banks in the past. any way how would i go about adjusting the cable, the light works fine on the switch and honestly it feels like there is no vacuum in the line.
i just want to figure out the real culprit before i purchase any parts.

 

There's no vacuum to the transfer case switch?
If there's vacuum to the 3 prong transfer switch you could bypass the switch, by using a vacuum hose as a jumper from the supply to the actuater hose and see if it moves the actuator up front.
Personally I think it's your $20 transfer case switch.

 

yea there is no vacuum to the actuator so it must be the switch. and that is trully the most obvious way to see if it is or isnt the actuator by bypassing the switch. thanx, i should have realized that.