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'04 Optima - 2.4L
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Discussion Starter #1
Did some searching and couldn't find anyone with this exact scenario...

'04 Optima, Electronic Climate Control.

My blower motor died (no continuity, kicks on briefly when hit on the back of the motor). While I was digging around in there, I pulled out the power transistor - it appears to be shot as well (assuming it's an NPN transistor???).

ANYWAY... the issue I have is that I'm reading voltage on the negative wire to for the blower - ranging from 1-4V depending on where the blower control is set. Same with the heatsink for the power transistor. Disconnecting the power transistor unit at the connector changes nothing. The voltage remains on the wire until the high speed relay kicks in, then it drops to 0. From red to black at the blower - Voltage starts at 12V on the lowest setting, then drops steadily to about 8V before the relay fires.

Looking at the wiring diagram, it appears as though the high speed relay and the power transistor share the same ground, so I'm at a loss here.



Disconnecting either of the relays has no effect either. The only thing I'm not sure about is the box marked "V". Anyone know what that's supposed to be? Is that the vent door? If so, that seems to be working correctly as well.

Anybody have any thoughts or insight here?

Thanks in advance!
 

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Super Moderator
2008 SpectraSX, 2014 Optima LX,2006 Jeep Liberty, Linux Mint Mate
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Ok...
My area of expertise....
The transistor is an NPN (arrow pointing away from center).
The Junctions on the transistor are as follows ...
Top one is the "Collector".a
Middle one is the "Base"
The bottom one is the "Emitter"
The current from the blower motor flows from the B+ through the fuse then the relay contacts to the positive connection on the blower motor. Then through the blower motor and out through the negative terminal on the blower motor. Then to the Collector junction on the transistor (it "looks" like the wire goes to the case (circle) of the transistor but it actually is connected to the top connection (Collector).It then passes through the transistor and out the "Emitter" (lower terminal) to ground...
The "Base" of the transistor is the control line that is varied in voltage from the "AC control unit" This varies the amount of current allowed through the transistor (collector to emitter) like a water valve controls the flow of water.
If you look at the two connections on the "Max HI Relay" they are connected to the Collector and the Emitter of the transistor. When the blower speed is set at "max" that relay closes the contacts and bypasses the transistor (C to E)and the blower runs full speed.
The transistor and the wiring going to it are subject to failure (burnt wiring and/or bad transistor)...If the wiring looks good then the transistor is probably at fault... I have NOT replaced one in an Optima so I don't know if the transistor is bolted to a socket and is easily replaceable or the wires are directly soldered to the transistor's legs...
I have seen posts where the transistor was replaced and that solved the speed problems... I believe you can get "just" the transistor at a KIA dealer.

The transistor will be mounted on some kind of heat sink (aluminum with fins) where the transistor is bolted down there should be either some silicon grease or a silicon pad between the transistor and the heat sink...This is an IMPORTANT item do not install the transistor without the silicon pad and/or the silicon grease..Their purpose is to conduct HEAT away from the transistor...Leave them out and you will have failures.
btw... The "box" with a "V" in the center is a DC Volt Meter used to measure the voltage across the blower motor.
The top relay turns on the blower motor circuit and the bottom relay provides HIGH Speed blower.
If the blower runs OK when the "highest speed" is selected then the transistor is probably bad...If it doesn't run at all the blower motor is probably bad.
Dave
 

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Discussion Starter #3
Thanks for that, DavesSpectra.

The transistor was mounted to a heatsink with the wires soldered to the leads. The entire unit consists of the transistor/heatsink, a fuse and an RC snubber. Apparently Kia is very proud of that little marvel of electronics, 'cause they want $115 for a new one. Mayhaps the heatsink was cast from unobtainium?

After staring at it for a while, the diagram makes perfect sense to me, with the exception of the lead that runs from the "A/C control unit" to just ABOVE the word "Power" on the diagram. From left to right: the first supplies voltage to the blower relay to turn on power to the fan. The third provides a control signal to the base of the power transistor (to control fan speed). The fourth provides a path to ground to activate the hi speed relay, which bypasses the transistor.

What's confusing me is the fact that I am reading voltage at the negative fan connection (with the fan unplugged). That voltage increases when the fan speed is turned up.

I installed a new fan and dropped in a 3055 transistor from my junk drawer (just for diagnostics, I know it won't hold up). I now have: off, 1 low speed and max speed.

I don't believe I'd have the low speed if the transistor wasn't working, so I guess I'll focus my attention on the mystery wire. Control panel diagnostics returns "00".
 

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2008 SpectraSX, 2014 Optima LX,2006 Jeep Liberty, Linux Mint Mate
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Ah yes the 2N3055 (T03 case) work horse. At 15amps current handling and over 60 volts VCEO that should be a good choice.

Think about "where" the AC control box gets it's operating voltage...and look at the diagram again...

You said" I now have: off, 1 low speed and max speed.
I don't believe I'd have the low speed if the transistor wasn't working"
Hit the nail right on the head...

I'd leave the 2N3055 in there if it doesn't get too hot...The only "other" type transistor that it might be is a Darlington type (two transistors in the same case with LOTs of gain) but that would be more expensive (bean counters) than an external one within the "box".

Good to "see" another "tech" here...always good to have one present with the new cars "flying by wire" (electronic accelerator pedals) and all the "new" electronic controls... A mechanic of 30 years past would not know how to address the new designs..

After reading your (and my) posts and seeing only a low and high speed for the blower...you may have the wrong transistor or internal damage to the "box".. are there any part #s on the transistor?? It might be a Darlington after all.
Dave
 

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2008 SpectraSX, 2014 Optima LX,2006 Jeep Liberty, Linux Mint Mate
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I see you are "just up the street" from me (Medina). I got an "04" Sonata (same beast with a 2.7L V6) for my daughter and rebuilt it (was salvage).. I also had fun with the green clock in the center dash going off and on...(bad foreign 1N1004 diode in the power supply)
Dave
 

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Discussion Starter #6
Well howdy, neighbor! Seems like every time I try to take my troubles to the international community, I end up getting help from someone right down the road. Don't know if that's because Ohioans are really smart... or just really bored!

I know all about the havoc a $0.03 part can cause. Just last weekend I was rushing to pass my eCheck: Check Engine codes were for both O2 sensors and the vent control solenoid. Replaced the sensors and pulled the vent control solenoid out (shearing a bolt off along the way)... which checked out OK. Buttoned it all back up. The check engine light was not impressed. $200 and half a Sunday into it, I went to the local autoparts store, where the 17 year old kid behind the counter said (without even thinking about it, mind you): "You checked the O2 sensor heater fuse, didn't you?".:blush-anim-cl:

Anyway, I looked at the pinout for the Black Box, and there is an output for "Power Transistor (C)" and "Power Transistor (B )", so it looks like that mystery wire is part of a monitor/regulator circuit for the fan. I definitely think you're right: I'm going to try to get my hands on a Darlington this weekend and see if that gets me a couple more fan speeds, otherwise I'll just have to try to wrangle up a new control unit. OR, maybe I can just wire in a single turn pot and have it sticking out of the dashboard somewhere.:whistling:
 

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2008 SpectraSX, 2014 Optima LX,2006 Jeep Liberty, Linux Mint Mate
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Nah...People in Ohio just want to help others. A good state to live in...

You said the counter guy said " "You checked the O2 sensor heater fuse, didn't you?"
One of my favorite sayings is "We tend to be human" and sometimes we miss the obvious. I'll also keep an eye on the O2 heater fuse for my daughter's car.
She lives in Akron. I have her car "titled" by me and in Stark County...NO pollution E-checks here.

Ref: missing speeds...
Is there voltage on the base with all speed selections? Does it go up with the speed selection? You need at least .6v difference (bias) between E and B for the transistor to go into conduction. You could put a control (pot) like a 5k linear pot in the circuit. The current through the pot should be extremely small. We are looking for only a voltage varying. One outside leg to +12v the other outside leg to ground and the wiper (center terminal) to the Base of the transistor. By varying the pot between the two extremes you should be able to control the blower speed.
btw... I am being overly simplistic as there are all levels of readers that may gain some knowledge from these posts...
This is a "global" forum...
Dave
 
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