Need Help With 99 Sebring Conv Problem

[jwoelfle]

I figure out of all the Dodge boys here, I can't be the only one with a 99 Sebring convertible. I've got a problem I'm trying to fix and I need some help. Here goes:



The problem is with the blower motor resistor pack... it doesn't work. I get blower motor only when the switch is set to high. Now I've put a new genuine Mopar resistor pack in it's place, and all switch settings worked for about 30 seconds... now we're back to high speed only. The thing that is confusing me is that there is a zener diode in this resistor pack... and it is the component that is failing. I know this for two reasons... 1) I checked the zener with a Fluke and found it to be open, and 2) I jumpered across the diode with a straight wire and get all speeds functioning properly.



Now the questions:



1) what keeps causing the zener to blow?



2) why the he!! is there a zener on a mechanical motor speed controller?



The only thing I can figure as to WHY the zener is even there, is if the LTD version of the car has some kind of automagic climate control... this JXi model does not... simple rotary, mechanical knobs.



Even if the zener doesn't need to be there in my application, why does it now all of a sudden start blowing them?



I'm so confused



Thanks,

Jim

 

[Steve M]

My guess would be the zener is used as a voltage regulator for the blower motor. It allows for example 12v to the motor and any voltage above 12v is bled off to ground. Why it's alluva sudden blowing zeners? Don't know since they go from the source to ground to begin with. Is your charging voltage too high? Might check that incase your voltage regulator isn't regulating. Shouldn't be more than about 14. 5vlts.

 

[jwoelfle]

Good point... I hadn't thought of the voltage regulator. I was focused on the system at hand and wasn't thinking outside the box.



Although I really don't see why more than 12v would hurt the motor, it is possible. I was thinking more along the lines of the zener being used to limit backflow... protecting some voltage sensitive computer part. I wish I had a shop manual so I could trace out the circuit. I'll try asking the stealer very nicely tomorrow if I can sneak a peak at a manual.



Thanks,

Jim

 

[wcaldwell]

Check your blower motor. My wife has a '99 Stratus ES - same car, different badging.

About a year ago, we had the same problem - blower on high only. We took it to Zangara Dodge - they replaced a computer "chip" and it worked for about 2 weeks. We took it back and they replaced a computer "chip" (notice a trend beginning?) and it worked for about a month. We took it back - I told them this was the third time for the same problem and it needs to be truly fixed this time and that I wasn't paying any extended warranty deductible. They pulled the blower motor and switch and replaced both. Said the blower motor had a "short" in the wiring. No charge. Haven't had any problems with it since.



Check your blower motor - probably the same problem.

 

[jwoelfle]

Thanks... after thinking about it more last night, that's the direction I'm leaning. When I plugged in the new resistor pack, everything worked but the low speed was REALLY low and then everything quit. So maybe it is drawing too much on the lower speeds due too bad bearing/worn brushes/commutator and burning out the diode? I've never seen a bearing on an electric motor go bad and not make any noise... this is as quite as can be, but I've experienced odder things in my life.



Thanks,

Jim