HVAC questions

Two questions about my 2000 Cherokee Sport... When I turn my heating/ac fan speed up to "4" I have hardly any air coming out of the ducts. I can hear the blower motor running at full speed so I know its not a motor or resistor issue. I am thinking the blower motor might not be seated all the way to the ducting and a lot of my "fan speed" is being lost inside the dash. How do I access the motor to figure out if this is in fact the issue?

Question 2 is whenever I change which vents the air comes out of (ie feet, face, windshield etc) my rpm drop substantially. Now I am sure this means the ducting is controlled by engine vacuum, so is this a tell tale sign of a vacuum leak? Any likely suspect lines I should check first?

Thanks

blower is accessed from under the hood-- bolted to the firewall. I'd guess that's not the problem, but I guess it can't hurt to check anyway.

I'd look for a HVAC duct that's not sealed and leaking.

Vacuum lines to check are between the intake and the front vacuum reservoir (football behind the bumper) and back to the heater controls under the dash. The usual culprit is the line to the football that runs under the battery tray-- acid eats it over time and some "hamfisted" flunky changing the battery breaks it without even knowing it 'til the lack of vacuum beging causing problems....... changed a battery recently?

Pretty sure "mode" is not vacuum operated in 2000. Have to check mine when I get home. Should be a actuator motor.

I thought the blend door was actuated with an electric motor and the location setting was still vacuum. I could be wrong, though....

Shorty said:

I thought the blend door was actuated with an electric motor and the location setting was still vacuum. I could be wrong, though....

Click to expand...

You're right. The mode selector is a dual function selector. It selects the various door positions by directing vacuum to the door actuators and it has an electrical 'wafer' that provides ground circuits for the fan speed switch and the AC select signal to the PCM.

The Blend-Air Door is operated by an electric servo motor on the '99+ XJ's, which is controlled by the Temp Selector on the control panel.

Looks like I posted in the right place lol. Thanks guys. Shorty ill check that line out today. I came down with a cold so I havent even looked at it yet since posting lol.

Prob caught a cold because I couldn't get heat out of my vents on 15 degree mornings lol

poppyseed said:

Two questions about my 2000 Cherokee Sport... When I turn my heating/ac fan speed up to "4" I have hardly any air coming out of the ducts. I can hear the blower motor running at full speed so I know its not a motor or resistor issue. I am thinking the blower motor might not be seated all the way to the ducting and a lot of my "fan speed" is being lost inside the dash. How do I access the motor to figure out if this is in fact the issue?

Question 2 is whenever I change which vents the air comes out of (ie feet, face, windshield etc) my rpm drop substantially. Now I am sure this means the ducting is controlled by engine vacuum, so is this a tell tale sign of a vacuum leak? Any likely suspect lines I should check first?

Thanks

Click to expand...

RPM droop may happen when selecting Defrost or Mix Defrost/Foot which will engage the AC Compressor if the outside air temp is above 30*F, so if this happens the IAC is supposed to adjust the idle to compensate for the additional engine load.

A vacuum leak in the HVAC vacuum source system shouldn't cause RPM droop, if anything I would think there would be an RPM increase due to a vacuum leak.

OK well I did some investigating and shorty was right on the money, attached is a pic of the vacuum line that was corroded and cracking right under the battery tray. I spliced in some soft vacuum hose from the parts store and I immediately noticed a difference when selecting HVAC "mode" I still have an RPM drop on occasion (prior it was every time) when selecting a mode which requires AC to be on. Now I have my clutch disconnected at the clutch itself to keep the ac from coming on (clutch cycles constantly when on, another issue for another day) I understand the IAC should allow the RPM to increase to compensate for the expected load. Since I am not actually increasing engine load one would assume my RPM would go up. Im wondering if my IAC may be faulty or gummed up since occasionally my RPM drops instead of increasing.



Also attached is a photo of my HVAC ducting behind the radio, does anyone else have this much of a gap between the ducts??

Thanks

damn-- it took you long enough to realize I'm always right......

no, my ducting doesn't have that much of a gap-- keep following it and you'll likely find that it's out of place somewhere else too and causing the loss of air flow.

whats interesting is everything was bolted in and very solid feeling. I would have to take apart a large portion of the dash to investigate further.

And I did laugh when I saw the hose was cracked right where you said it would be haha.

you'll sadly have to start at the blower motor and work your way through it to find the loss of air-- unless you're getting water into the cab, your blower motor probably isn't loose enough to cause any loss of air flow.

sack up and get that beautiful bride of yours to keep you warm

Shes the one im fixing it for, its "her jeep" now lol I get the sweet 2002 cavalier