Blower runs off battery just fine.

 

Hmmm then my guess is you have a major voltage drop. Connect the blower and back probe the connector with it on and tell me what the voltage is.

 

There's obviously a short somewhere, as shown by the tests already done. It has the potential to hold the voltage but it's just not getting the power. Installing a line from the battery with a relay in line would cut out the short.

 

Try leaving the power connector attached to the motor (pin A) and disconnect the ground connector. Make a jumper that will go from the ground pin on the blower (pin B) to the battery negative post. Then try operating the fan - with switch to RUN. This is not hotwiring the blower from the battery, but using the HVAC controls to provide the power.

If the blower works good the ground circuit is bad (blower resistor pack, or its wiring, maybe), if it doesn't work full speed the power circuit is bad.

 

You are aware that a short means the power is going to ground before it gets to the motor? In this case I do not think a short is possible.

Based on the low voltage I suspect a poor connection, a damaged wire ie broken strands, or more likely a bad relay. It could even be the resister pack... or the harness connector for it as chrysler vehicles had all kinds of problems with those.

 

I've tested the blower in that fashion with no luck. I definitely think the short is on the power side.

 

Once again you are confusing short with high resistance. A short on the power side would blow the fuse. Have you tried a new or diff relay?

I still think based on the symptoms that you are dealing with a high resistance that is dropping enough voltage to keep the blower from operating.

Here is a good video series on voltage drop and how circuits work. Electrical electronics:

 

I'm sorry I'm using the wrong term. The resistance is on the power side and yes I've tried a new relay as well.

 

You are right. I was just using the wrong term. I apologize. The resistance is on the power side. What is next then? Should I test each component and find where the voltage is being lost?

 

Yep watch the video series i posted in the post above yours. I think then you will better understand how to test for your voltage drop or resistance issue.

 

I'm on my iPhone and it says it can't be viewed. Can you just post the hyperlink?

Judging by the schematics, the only place the power line passes through is the relay . Can I test it there?

 

voltage drop is measure inline with the circuit and is a way to determine how much voltage each connection and device is consuming. If you have more than .5 volts of drop in most circuits not counting the main load you have too much.

 

Yes.

Refer to the HVAC Blower Circuit schematic.

See the blower relay pin configuration. Pin cavity 30 is power directly off of the battery bus, as it passes through fuse 6, 40 Amp, in the PDC.

Remove the relay and locate pin cavity 30 in the relay socket. Measure the voltage from cav 30 to a structure ground. It should be battery voltage. If not, note that the power wire, Red/Light Green tracer, passes through connector C209 (Green connector behind the glove box). If you don't see battery voltage at relay cav 30, the next step would be to disconnect C209 and check voltage back to fuse 6 at C209 pin 8.

 

At Pin 30 I got nothing, car off or on. At 87, I was getting about 11. Going from 87 to 30(negative) I was reading about 10.5

 

Is it somehow possible that 30 and 87 somehow got switched elsewhere in the wiring? Or is 30 simply where the power is being lost?