Girlfriend's '04 Grand Cherokee Limited is having HVAC issues. The blower motor resistor was fried to I replaced it with the new updated unit along with the retrofit kit. Now the HVAC works but it doesn't blow very hard. Thought it might be the blower motor so I pulled it but it seem fine. Threw a new blower motor in and it didn't do any better. Ideas?

 

Relay, fuse, bad new resistor, bad wire, blend door, clogged/ disconnected duct? Does the motor blow hard out of the vehicle? How does the squirrel-cage look?

 

Motor blows hard out of the vehicle. Squirrel-cage looks fine other then having just a bit of dust on it. You can hear the blower motor going at full speed and at each interval in-between full and off so the blower motor resistor should be good.

 

Hmmm, Seems like you covered all areas.

 

It's a bit weird. Only thing I need to check is that the polarity on the fan isn't reversed. She had brought it into the dealer for the HVAC issue. They said it was the blower motor resistor which of course is the one thing on the HVAC system that isn't covered under her warranty and wanted $600 to fix it. I picked it up and did it myself but there's a chance the stealership intentionally messed something up since we wouldn't pay them to fix the issue. She doesn't have the add-on cabin air filter so it's not an issue with a clogged air filter and I've checked the area where the filter would be installed for debris and found it's clear.

 

It is that new resistor you put in. That is what controls fan speed

 

No it's not. If the resistor is bad, the fan will only operate at full speed. Even at full speed the vents are pulling out just a little bit of air.

 

Have you checked your vacuum lines to make sure the HVAC diverters are opening to the full position you select?

It could be stuck partway blowing to the floor or defroster vents. The air is going to take the path of least resistance unless it is blocked off and sent to a specific place.

Check the dampers and the vac lines and make sure they are operating through their entire range

 

[QUOTE=NotMine;354631 The blower motor resistor was fried to I replaced it with the new updated unit along with the retrofit kit. Ideas?[/QUOTE]

The idea was that this resistor is not the original. It is an update. Try the OEM. And yes it does control fan speed, through its resistance. If you want to really check it out, take an ohm meter and check an OEM with the updated model. If the new one has more resistance, well then it is the culprit.

 

It is an OEM blower motor resistor. They updated it to a new design with longer heatsinks and a smaller length and width. A small adaptor plate is used to fit it in the old resistor's spot.

I don't believe it's an issue of the blower motor resistor. The resistor is used to control fan speed between high and off. If you remove the resistor all together, the fan will only operate at full speed or not at all.

 

I'll check them out today. Also going to try calibrating automatic-climate control door actuators and running the self-diagnostic.

 

Calibrated the automatic-climate control door actuators and ran the self-diagnostic. Diagnostic showed no fault codes. Still doesn't seem to be blowing very hard.

 

I have the exact same problem. But, I don't see a resolution on this forum. Did you fix it? I'm thinking it's either one of the dampers/doors or the blower is blowing backwards, maybe?

And the diagnostics on the AC control show:
14
51

 

I guess you could have a reversed polarity thing, If you took the blower motor out, keep it plugged in and turn on and see how the air is moving. The air flow should be blowing out and away from cage. Some fan cages even have a direction arrow.

Did you check the Cabin air filter. If the filter is dirty it may be restricting air flow. I think you would still have good air volume in the MAX position though, because it recirculates air and not through the fresh air inlet/cabin filter (I think?) The filter is under the wiper cowl panel on the passenger side, you will need to remove the RH wiper arm and pull out the RH cowl panel to access the filter.

 

Turned out that from the factory, the color of the wires on one side of the blower motor resistor I replaced were switched around. Everything appeared to be connected right but the polarity was reversed because of it so the motor was spinning in reverse. 10+ hours of ripping apart the dash for nothing.