Help with cab Heating

[RustStang78]

Basics: 89 Laredo, 4.0, Aw4, 242.

I replaced the blower motor as it's bearings were singing, and ever since I have no noticable airflow in the ductwork. However, when the jeep is warming up with the heat on, the cab is comfortable after 10 minutes, I just don't have any air flow... I checked for:

vacuum leaks - none

blower motor working - it spins at all four speed settings

Fan blade - still attached to motor and it is spinning

vacuum actuator under blower motor in cab - it doesn't move (what does it do?)

Temp control switch - it moves some baffle (I hear it move)

Fuse - still good (replaced it once which lead me to realize the old motor was drawing too much current)

But when I place my hands over any vents, zero air velocity...


Any ideas???

 

[87manche]

I believe the vacuum actuator is what moves the door for the vent selection. Try moving the rod by hand and see what you get out of the vents.

 

[shanesaw]

I'd bet it's a broken or disconnected vacuum line. There should be two that run from the cabin to the engine bay through the firewall above the heater core fittings that ultimately end up at the vacuum canister. Those run to the dash controls along the top of the HVAC housing. The ones inside are very difficult to get to, so check the ones running in the engine bay first.

 

[Ecomike]

You bropably damaged the vacuum lines leading to through the firewall going to AC/heat duct system than run the vacuum actuator for the duct baffles. The lines are right above the blower motor!!!!!

 

[RustStang78]

well I gave it another try this weekend when I had more time and I found the following with the fan on:

- Nice strong air flow out of the vents at the bottom of the windshield (I figure that's how I was getting the heat into the cab during engine warmup)

- The vacuum I had when I took the hose off the vaccuum accuator is now gone, not even a hiss.

- I had no noticable difference with the other vents when I manual move the flap connected to the vacuum actuator.

so based on the lose of vacuum, looks like I need to do some digging...