Defrost blower only. Checked for vacuum leak, etc.. still need help.

OK, on my son's 87 Waggy, 4.0, Auto, 4wd....

I've been reading all the posts regarding the heater/defrost/ac blower only blowing out the default defrost vents. Also, I checked and could not find any vacuum leaks anywhere. All the vacuum lines in the engine bay, under the passenger side bumper, etc are all in tact and not leaking. Although I have no idea what that canister (that the vacuum lines attach to) in the front bumper is or what it's suppose to do, or how to check it..???..???

I also pulled the radio and vent control unit out of the dash and couldn't find any broken or loose vacuum lines. There is a vacuum line plugged into something under the kick panel on the passenger side front. Made sure the cluster of vacuum lines on the backside of the control unit are plugged in they didn't appear to be faulty or corroded.

I'm at a loss here. Could it be the control unit is faulty w/the wiring that I'm assuming gives signals to the vacuum lines? The blower works in all positions (low to high) ... I don't want my kid freezing this winter so any suggestions would be appreciated.

Thanks.

I bet it's your canister. It's behind the passenger front bumper. Just look up in there and make sure the lines on either end are attached. If they are and you still only have defrost, switch them around.

check them again. start at the canister. its the black "football looking thingy" located behind the pass side of the front bumper. check by spraying with water and looking for the leak. next fallow the lines coming out of the vac canister the same way. check the entire length of the line. consentrate on any bends or connections including the back of the ac unit where the vac lines come in.

hth

My canister looked fine till I pulled it off, then I found a crack where the foot meets the actual bottle. I replaced the bottle but I also kept the old one and plan to see if I can epoxy it back together.

Hey I went through two winters with no vaccum canister and I didn't freeze!!

Heat still comes out, I just drove hunched over the wheel haha

Guess how annoying it was to start from the hvac control end and get to the bumper just to find that there WAS NO CANISTER

Thanks guys... I'll go and check again and pull the canister off and see if it's cracked.

Can anyone tell me what this 'canister' does? Is it just loosely laying in there (it appeared to be) or is there a strap or something holding it in?

Redsnake said:

Thanks guys... I'll go and check again and pull the canister off and see if it's cracked.

Can anyone tell me what this 'canister' does? Is it just loosely laying in there (it appeared to be) or is there a strap or something holding it in?

Click to expand...

It bolts to the bumper with two (IIRC) 10mm bolts. When you get the end cap off you will understand.

The vacuum connection (its an L adapter) was mashed too far down onto the vacuum line on mine, right by the passenger side firewall......simply cut the vacuum line where it was crimped, slid the L adapter back on, and that fixed my problem!

check for a clogged line. my buddies vac line was clogged with dirt (no idea how it got in there) right where it enters the intake manifold.

Thanks guys... there are also these small round canister like things that are in the middle of the vacuum lines in the engine bay that seem to be plugged. I actually disconnected the vacuum line w/the intake manifold and tried blowing down the line w/my air compressor and it wouldn't work until it blew the vacuum line off that little canister.

Also, when I tried blowing air thru the vacuum line into the 'football like canister' in the front bumper it wouldn't do anything either and actually blew the vacuum line off the canister. Should the air flow throughout the vacuum line easily or is it normal to react like I described?