Bizarre A/C and heating problem

[88shagwag]

Ok first off any help would be appreciated with knowledge of such a problem. Last summer I was running my ac and it would suddenly quit. You could cut it off and then back on and it would usually start right up again. I ran the heater all winter no problems. I went to cut on the defrost the other day and nothing happened. I switched to ac then heat and nothing, no blower motor activity at all. I have checked the fuse and checked the circuit breakers with an ohmmeter for continuity and they were all fine. I got a new 30 amp relay and replaced every one of the three 30 amp relays one at a time to no avail. I then pulled the heater and air conditioner control assembly and replaced it with one that i tested in an 89 grand wag that was working. Still Nothing!!! What am i missing? I know that there are blower motor resistors for the heat and the ac but I find it hard to believe they would both go at the same time. Do I have a grounding issue? Please, any good info is really appreciated! Thanks

[FSJ Guy]

Check the connectors to the blower motor resistors. The heater blower resistor array is on the heater core box inside the engine compartment. The A/C blower resistor array is on the driver's side A/C duct. It's on the back of the duct, IIRC.

[babywag]

Does the AC compressor clutch kick on?

Checked for power @ the blower motor wiring plug(s)?
Both of them...

[ScottsMojo]

If it were me, I would get the proper wiring schematic for my model year and start tracing the HVAC/heater circuits from the controls forward. Do you have voltage to the switch(s)? Do you have voltage to the components? Electrical wiring is not as intimidating as you think it is, it is a logical process of elimination when it comes to troubleshooting, most of the time... You might find the schematics for your Wag here http://oljeep.com/gw/elec/GW_wiring.html...

Best of luck!

[ShawnQ]

My jeep has the same issue, no a/c or heat controls at all...subscribing to hear the outcome!

I haven't had a chance to research mine at all yet.

[88shagwag]

When I originally posted I had already checked for power at the heater blower motor plug and checked the resistor connections. I haven't had time to mess with it since my post which sucks because it is my daily driver. All the stuff is just hanging out like it was being stolen!

[FSJunkie]

You know the A/C and heater each have their own blower motors, right?

The heater blower is in the engien compartment and pulls its air from the cowell intake only. The A/C blower in on the top side of the evaporator under the dash and pulls its air from the passenger's stinky feet area only.

[88shagwag]

I am not getting power at the 25amp fuse in the fuse housing. All the fusable links are good and i can't figure this out!!!! Yes i know there are two resistors. None of this would have anything to do with no power at the fuse right??? I checked all three red wires coming into the back of the fuse bulkhead and they are all hot. I am going to have to really start taking things apart I'm afraid! Thanks for the replies guys. Still love some advice!

[serehill]

Sounds like internal bus damage in the fuse block or the splice where the wire from the alternator splices to the steering column headlight & fuse block is messed up. That is less likely than the messed up bus. The bus is the main runner in the fuse block the clips attach to. The clips are what the fuse fits in. The clips can & do come loose. You can get a small fuse panel & attach to the red wire coming from the alternator & make new circuits if that is the case. You should be able to take a voltmeter & test the fuse block. Check both sides with the fuse out one side should be hot the other not. If it is hot then the load side my be fried. Tracing the wires & building a new circuit or replacing the fuse panel is the solution if you find this to be the case.

http://www.powerwerx.com/fuses-circuit- ... 4AodxRgAOg

[88shagwag]

Thanks serehill, no power on either side of the fuse clips when key is in the on position. I guess I'm gonna have to start digging deep into this! If there is a glitch in the key positions meaning acc, start , on, could that affect the power to the fuse? It should still be hot correct if all the other fuses go hot when turned on right?

[FSJ Guy]

If there is a glitch in the key positions meaning acc, start , on, could that affect the power to the fuse? It should still be hot correct if all the other fuses go hot when turned on right?

Not necessarily. The ignition switch (switch above column, under dash, not the key "switch") has multiple contacts for several circuits. One could be broken while the others still work.