I searched the forums but didn't see similar threads - so if this is re-visiting something already discussed I apologize.

I have a problem with my heater/AC fan (in a 97 Rodeo/Passport) it no longer kicks on to blow cold/hot air. If the AC is on, I can feel cold air 'oozing' out but it definately isn't forced. The sytem has been on the fritz for a few weeks now, and whenever the fan had stopped in the past I could flick my recirc/fresh air switch a few times and then the fan would kick on - and all speeds would work. Now that it's hotter than ever, the recirc switch trick no longer works!

Before I get in there - any ideas? Bad switches in the dash control unit, or a bad fan (or fan connection)? Any trouble shooting tips?

Thanks - appreciate any info/tips.

Nothing specific, but here's some general electric troubleshooting tips that apply.

Troubleshooting electrics requires methodic testing so you dont end up pulling your hair out. Confirm what you think you know and test what you don't, and move in methodic steps. required tool is a multimeter and set it to measure Voltage.



I'm assuming this circuit is made up of battery, fuse box/relay, resistor pack to give you speeds, amd switch. There might be more to it than that and a schematic diagram will help.

There is basically a circuit for the power to the blower, and a "subcircuit" to switch the relay. Two individual circuits that need to work together.

Step one is to plunge in the middle of the circuit to tell you which way to go. Pull the blower relay. The socket will have 4 terminals. One pair for switched power to blower, and one for the switch power. While the switch is on, you should have power across both pairs of connectors. If not, you either have a fault in the swicthing circuit or the blower power circuit.

Basically, if yes, then move a step closer in the circuit towards the blower; if ''no' move a step backward in the circuit to the source (battery).,

So you get all the way to the blower with 12V but the thing doesn't work, the blower motor is shot. if you trace the switch circuit all the way back and get 12 V tehn the switch is shot. Does this make sense?

Also, you can confirm anything you know by jumping power from the battery directly where you are.

Say you have determined there is 12V at the relay for the blower but not across the switch circuit. You could jump the relay with leads driect from teh battery and you would narrow it down to the swicth circuit. go slow and don't skip any steps if you arte organized you will track down the problem.

well, seems like you got narrowed down already to the switch. at least, that's where i'd start. is it mechanical or electronic...can you clean some contacts in there? suggest jumping the connections at the switch and see what happens.

good luck

see I'm hesitant to start there since that is either mechanical for little flapper things or electrical with solenoid-driven valves. i can't see how they would have any relation to each other and I bet if you keep following that circuit you might get off track. we'll see though.

Thanks guys. I'm going to start digging in tomorrow. Further research indicates that I need to get behind the glovebox and see what kind of voltage is being given to the blower motor. IE: disconnect and see if its getting any. If not, the switch is bad.

I picked up a Haynes manual that has the circuit diagram, and will start tracing from there - which is essentially what was recommended.

Gut feeling is that it's the switch panel. If so - then from what I've seen that's fairly easy to replace, but more expensive than a relay.

Well - I guess you can't have your cake and eat it too. Unless, you went and bought your own cake, right? Or.. something. LOL

I'll write back with an update in case anyone has problems similar to this in the future.

-Gary

Any updates?

My fan stopped working yesterday as well, but I can feel AC (cold air) flowing through when I open to vent in outside air. I can also hear the AC turn on, but no forced air <img src="/forums/images/graemlins/frown.gif" alt="" />

Your 97 systems must be different than the 95.5. On mine, the AC won't even turn on unless the fan is running, and the fan will not turn unless the control relay senses proper charging current coming out of the alternator. The logic is that the fan is a very large current draw, and without a working alternator, it will not run it. The AC compressor is relay controlled from the fan switch, so no fan, no AC either.