Only one HVAC speed does not work

[advcomp2019]

This issue is a little confusing me for months. I finally decided to post this issue.

I have tried everything it seems: different resistors, testing resistors, different switches, testing switches, testing wires, and etc. It seems like only number 2 on the blower control on the manual control HVAC system does not work. All the other speeds work just fine. At first, I thought speed 1 did not work, but it still works.

 

[Mooseman]

I would assume you have the manual system? If I understand you right, you replaced the resistor and the switch? Have to checked power output to the tan wire into the resistor?

 

[advcomp2019]

Yep. I have tested that wire, and even the other wires.

 

[Mooseman]

And you replaced the resistor pack?

 

[advcomp2019]

Yep. Still no number 2. That was the first thing that I thought. That is when I seen all the other speeds work when put a voltage meter on the blower plug.

 

[Mooseman]

Looking at the schematic, it has to work if 12V+ is applied to that tan wire at the resistor. Did you check the connector that goes into the resistor? They sometimes melt or wires break.

 

[christo829]

If you didn't replace the connector, I'm seconding Mooseman's suggestion that you check the connector. If the metal inside the plastic connector housing gets hot, it can start to melt the plastic, so the metal can shift and stop making contact. If you probe it, you may still read voltage, but it doesn't complete the circuit when you plug it in.

Good Luck!

Chris

 

[jsheahawk]

If you didn't replace the connector, I'm seconding Mooseman's suggestion that you check the connector. If the metal inside the plastic connector housing gets hot, it can start to melt the plastic, so the metal can shift and stop making contact. If you probe it, you may still read voltage, but it doesn't complete the circuit when you plug it in.

Good Luck!

Chris

Third. They usually get black and obviously burnt but not always.

 

[advcomp2019]

I was double checking for melted plastic or corrosion today, and there is none that I can find on the either plugs.

I am getting about 12 volts to the plug at the resistor plug. Plus, I am getting voltage at all speeds at the blower motor plug.

I can take some photos if you want too.

 

[budwich]

photos yes.... glasses during your testing yes ...

 

[advcomp2019]

Resistor plug on the wiring harness: Photo 1 Photo 2 Photo 3
Resistor: Photo
Blower plug from the resistor: Photo 1 Photo 2
Voltage to the resistor: Photo
Voltage at the blower: Photo

Sorry for the glare on some of the photos. I had to use a cell phone camera since I did not want to get my better camera out. Plus I did not feel like removing the resistor since it is a little hard to get it up into the dash since it is a tight space.

Hope this helps. If not, just ask me to look at something else.

 

[budwich]

get a 12v bulb and socket. Hook it up in place of the motor.... go thru the speeds and watch the light. Like others have indicated, it appears you have a "current carrying issue".
still further how are hooking up your meter to do your measurements (ie. where exactly are the probes touching?). The reason that I ask, is that you should not be seeing 12v for all speeds so your "testing" is suspect.

 

[advcomp2019]

On the resistor, I am going from the front side on the black wire aka ground and back and front side of the tan wire. On the blower, I am going from the back side since the front side does not fit the probes. It feel like it is a really tight fit if I do tho.

 

[budwich]

OK... so what the motor readings for each speed that you select?

 

[djthumper]

I would replace the plug from the switch to the resistor. I think you may have had a wire that is broken, the plug looks fine so you need to find the break in the wire.

 

[advcomp2019]

I finally decided back probe the blower connection with the blower connected to see what happened since I have not done that yet. When I back probe the blower connection with the blower connected, I got 3 volts on 1, 4.6 volts on 2, 6.5 volts on 3, 8.1 volts on 4, and 11.1 volts on 5. They was jumping all over the place. So give and take about .2 volts since most of them was jumping that much but for speed 5.

 

[budwich]

the voltages should all show the same characteristic as the "5" (ie. steady). Next, a picture of the resistor pack please. Lastly, what about the blower relay?

 

[advcomp2019]

Not sure what or how this happened, but I got number 2 working again. All I did was disassembled the resistor plug on the wiring harness side, and checked for any issues behind the plastic plug that we can't see. Since I found nothing, I put it back together. Now, I have speed number 2. So I am not sure if this issue will come back or not yet. So I hope it will not come back.

 

[christo829]

If you end up taking that connector off again (which hopefully you won't have to), wiggle the wire for the second speed and see if the metal connector can
move side to side or forward/back. If the previous resistor pack created enough heat, it could have softened and deformed the plastic around the metal enough
to cause it to not make a firm connection consistently without obvious scorching or melting.

In any case, glad it's working again!

Cheers-

Chris

 

[advcomp2019]

Yea, I am wondering if the number two is a little deformed without showing it too. If it happens again, I might look into any play into the number 2. Then I will try to figure out a fix that is not much money, and will not mess up the wiring too much.