Hvac problems...

[Hartleybl]

Hey guys i got another problem with my 04 CC.... the blower motor does not work on 1 or 2... works great on 3 and 4... but as soon as you start moving... like 10mph and up... you can feel it start to blow air thru the vents.... Not on Max A/C but everything else it will flow air on 1-2 as long as your moving.... you cant hear the blower motor working until you put on 3-4... then Max A/C works also... im so confused.... ive tryed tapping on the blower motor...everything i can think of exept cutting the houseing under the hood open and preforming surgery on it lol... any idea's ?

[HenryJ]

I am a little confused, but it sounds like you may have a couple problems?
Your vacuum system may have leaks. That affects the operation of the HVAC doors. Look behind the brake booster in the engine compartment for dry rotted hoses.
Next sounds like your HVAC resistors are fried? Those change the voltage to the blower motor for the different speeds. Pretty common for those to fail.

Wild cards: Blower motor failure, blower motor switch bad, trans fluid in the HVAC controls.

Check them all out.

[Hartleybl]

thanks.. i changed out a section of the vac hose at the little T it was almost broke in half... it helped alot... didnt notice any fluid in the lines but im gonna take my dash apart and check the hoses running to the dash controls and check the resistors hope it isnt to costly thanks and Happy thanksgiving

[HenryJ]

Crawl underneath and check the "triple hose" connected to the transfercase switch. That is where the fluid will be coming from.

The blower motor resistors are not terribly expensive. Under $20 and available at your local auto parts store. Look closely at the connector. If the hot wire is burned the connector may need to be repaired or replaced. Full size had a problem where the wire size was too small and it would overheat at the connector. There is an upgrade connector available for that repair.

[Hartleybl]

thanks i crawled under it and looked everything is dry .. exept for the rear main... lol a little bit of teflon tape on the t-case filler plug seems to have fixed that leak... i unpluged the big 4 prong plug from the hvac housing... everything nice and shiny no burned spots where do i find the resistors ?

[Hartleybl]

also i looked for the paint mark on the t-case vac switch... didnt see a blue or green.. no paint mark at all... but i didnt take it out.. it wasnt leaking so i didnt want to mess with it to much

[HenryJ]

The leak is interior, not exterior. Fluid is sucked into the HVAC system destroying the slaves and controls. $1800 in repairs for a $20 switch failing. Read the transfercase switch thread for more.

[Hartleybl]

Crawl underneath and check the "triple hose" connected to the transfercase switch. That is where the fluid will be coming from.

No fluid leaking from here... guess i'll take the dash apart tommarow... i was hoping to not have to take it apart... they usually sqeak and rattle after you take them apart.... atleast the last 2 s-10's i had did...i checked all my fuses... 3 hvac fuses... 30amp under hood, 20amp and 10 amp in dash.... and to my surprise.. the Aux isnt wired up... i guess they changed alot in 04

[Hartleybl]

ok i took my dash apart no fluid in any of my vaccum lines... took volt meter checked the wires running to the 1-2-3-4 switch... got voltage up to the switch still cant figure out why 1-2 dont work...

[HenryJ]

... still cant figure out why 1-2 dont work...

The heater resistor is bad?



MPE BR237SB - AC Blower Motor Resistor

[Hartleybl]

just checked it... 1-2-4 reads voltage to only one part of it.. 3 reads voltage on all parts of it... but it blows on 3 and 4

[HenryJ]

High is run through a relay to provide the full 12 volts. It is not a part of that resistor. Lower settings run through that series of resistors to change the voltage and as a result the blower speed.
Think of that little block as a series of pipes A big one that flows quite a bit, but not full, down to a tiny pipe that flows just a little. Measuring resistance , not voltage through the blower motor resistor is the way to check it.
I would suggest pulling it out and inspecting it. You may be able to tell how it works and connect an ohm meter to it for testing.

If you are having trouble with lower speeds...that is the item that gives you those speeds. The switch only sends 12 volts to this after selecting the speed. This resistor sends the power to the blower at that selected speed.

There are only three components in this puzzle. The switch, resistor and blower motor. You already said that it blows on high, so the high fan relay is working and out of the running. The blower is blowing, so the motor works. That eliminates it. The switch does work on , I assume, 0 , "3 and 4", so it is at least functioning 60%. That leaves the resistor suspect. Thus far you can not say it works in more than one resistance (3). That puts it in the lead at only 30% functional. I suggest it is the place I would focus my attention at this point.

[Hartleybl]

Thanks i'll change it out when i can afford one.. money is tight right now so i'll just have to live with 3-4 for the time being, thanks for all the help

[HenryJ]

Do the connections look burned in the plug?

[Hartleybl]

No they look like new no burned or discolored spots... just shinny silver on the resistor .....and the ones on the in dash 1-2-3-4 switch look fine also... no burn marks or discoloration

[shguiuc115]

The blower did not work on 1-2, then stopped working even on 3-4. Replaced fuse, it blew right away. Changed fuse again along with relay and resistor. All speeds worked for a week.
Now 1-2 do not work again. What do I check before replacing the resistor again?

[HenryJ]

Blower motor?