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1989 Dodge Dakota 3.9 2WD. The A/C blows nice and cold (48) on ALL fan speeds but HIGH. When I put it on high, the blower continues to blow, but the A/C clutch turns off. Once I lower the fan speed, the clutch kicks back on and everything is cool again!
I wonder if your hvac controls are faulty causing power to the A/C clutch to be lost.
I would try connecting a voltage meter to the clutch connector. red lead to the hot pin and black lead to battery negative.
See if your getting any voltage at all.. also try wigging the switch between medium and high. You need to position your meter where it can be seen from the driver seat.
You should be able to run tests with the Key ON, Engine OFF so you don't have to worry about getting wrapped up in the belt and fans.
Do all four fan speeds work? You should have HI, M2, M1 and LOW.
Looking at the diagram it looks like there is a common ground rail (highlighted yellow) that is closed when the blower switch is in any position but off. This ground or "A/C call signal" must also be passed through either the A/C or DEF switch for the electronic cycling clutch switch to be enabled.
Since the concern is that the clutch works on all blower speeds but High makes me suspect that the ground rail for the A/C is loosing contact in that position. (Try wigging the switch while in high?)
Also since the A/C Clutch is powered by an ECM controlled relay and not directly by the hvac controls.. testing out at the clutch connector isn't that useful but, instead out at the hvac control itself would be a better choice.
Last edited by dodgem880; Sep 4, 2023 at 08:59 PM.
Do all four fan speeds work? You should have HI, M2, M1 and LOW.
Looking at the diagram it looks like there is a common ground rail (highlighted yellow) that is closed when the blower switch is in any position but off. This ground or "A/C call signal" must also be passed through either the A/C or DEF switch for the electronic cycling clutch switch to be enabled.
Since the concern is that the clutch works on all blower speeds but High makes me suspect that the ground rail for the A/C is loosing contact in that position. (Try wigging the switch while in high?)
Also since the A/C Clutch is powered by an ECM controlled relay and not directly by the hvac controls.. testing out at the clutch connector isn't that useful but, instead out at the hvac control itself would be a better choice.
1989 Dodge Dakota 3.9 2WD. The A/C blows nice and cold (48) on ALL fan speeds but HIGH. When I put it on high, the blower continues to blow, but the A/C clutch turns off. Once I lower the fan speed, the clutch kicks back on and everything is cool again!
*************It seems the blower resistor was the issue. All great info provided! Thanks******************
Glad it worked!! The blower will go on even with a bad resistor as you found because the coil will freeze up without warm air present. A fail safe that could be confusing when other speeds work.
