Blower motor diagnosis?

[Jimmy9190]

This is for my 2001 Dodge Dakota, 148,600 miles on it.

The first and second speeds on the blower fan motor for the heat/AC in my truck have hardly any output. This happened all of a sudden last week. I suspect the blower motor resistor pack is bad. It is a very common problem on Dodge Dakotas.

The fan itself turns, and works OK on the third and highest speeds but does not move as much air as it did before. I just wonder is that the best diagnosis I can do, in other words if the fan turns it is OK, or can the motor still be bad, but still work well enough for it to run and turn the squirrel cage? There are no abnormal noises or vibrations from the fan motor, but it does not move as much air as it used to.

I am going to remove and check the fan tomorrow and replace the resistor pack if it needs it. I appreciate any help or ideas you have on on the fan operation. Thanks.

 

[eljefino]

The older boxy dakotas have a huge 8 position plug under the hood; this corrodes all the time. Not sure how yours does it, but it's the first thing I'd check. This could be your resistor block.

 

[Jimmy9190]

On my truck the fan motor and resistor pack are both mounted on the bottom side of the HVAC housing, above the passenger's side footwell. Both are very easy to remove. I have already replaced the resistor pack once before, about 4 years ago with a genuine OEM Mopar resistor pack.

 

[JHZR2]

sounds like when brushes go.

 

[sleddriver]

Not sure if this applies to your vehicle or not, but if it has a cabin air filter, when was the last time it was changed? I've seen some of these that were downright clogged as the owners forgot about them. A really dirty one will definitely restrict the airflow out of your vents, especially on the lower speeds.

Also, if you have a DC ammeter, check the motor current draw on each speed.

 

[mechtech2]

You are right to check the connector and resistor pack first.
When the resistor goes, the fan stops, and things over heat. this makes things even worse, and the connector can melt.

 

[Jimmy9190]

My truck does not have a cabin air filter. I do have a Fluke meter, it can check current draw to 15 amps but one of the fuses on my meter is blown, and no store in my town carries the right fuse for it. I can not check the current draw of the blower until I can replace the fuse in my meter.

I have no burned wires or connections at the resistor harness connector and the fan itself was running in all 4 speeds with no noise, it just had lower than normal output on the low and second highest speeds. I took the fan out and did not find any leaves or other obstructions in the squirrel cage. There is no wobble or anything in the fan as it spins and it does not get hot, or even warm when it is running. All of that made me think the fan itself is probably OK, so I decided to shotgun it and bought a new resistor pack at Advance. The new resistor pack looks exactly like the OEM Dodge resistor pack.

The fan seems to be doing better now, all 4 fan speeds feel like they are a somewhat stronger than before but I need to drive the truck and find out for sure I guess. Hopefully I can find the fuse I need soon and then check the current draw of the fan. If the fan checks out OK but I still have air flow problems then I guess the only other thing it could be is the fan knob on the control panel. Thanks for your help.

 

[sleddriver]

Originally Posted By: Jimmy9190
My truck does not have a cabin air filter. I do have a Fluke meter, it can check current draw to 15 amps but one of the fuses on my meter is blown, and no store in my town carries the right fuse for it. I can not check the current draw of the blower until I can replace the fuse in my meter.
Try Mouser Electronics, Digi-key, Frys on-line or Tequipment.net for a new fuse for your Fluke. Buy extras as they usually pop when you need them the most.

 

[ltslimjim]

My 1-2 speeds, especially in the coldest weather, seem to generate a 'flickering' like noise, but goes away when hot. Bearing? Motor resistor? Higher speeds less/no noise.

 

[Jimmy9190]

I just used a Sears store credit/easy exchange card I had from Christmas to buy this clamp style ammeter online from Sears:

http://www.sears.com/shc/s/p_10153_12605_03482369000P?prdNo=1&blockNo=1&blockType=G1

It will test current up to 400 amps plus has a volt meter and some other good functions too. I am going to visit family tomorrow and can stop at Sears on the way, we will be driving right by the store.

This meter should come in handy, not only for checking my blower fan but also for any other electrical troubleshooting I need to do. I also saved an extra $5.00 on it by using an online discount code from retailmenot.com.

 

[Jimmy9190]

I used my new clamp ammeter today and found these current amounts on the positive wire of my blower fan with the AC on:

lowest speed 4.5 amps
2nd highest speed 8.5 amps
3rd highest speed 12.4 amps
4th highest speed it read 20.4 amps

I checked the readings twice to be sure it was correct.

The blower fan has a 40 amp fuse in the Power Distribution Center. I read online that 20 amps of current with the fan on high speed is about normal. Hopefully the new resistor pack was all I needed to fix the fan problem.

Thanks for your help on this.

 

[ltslimjim]

I believe the resistor may be the culprit on my car, but symptoms haven't been bad like last winter so we'll see. Cold weather = fan noise?

Thanks for the update on the results. Post your conclusions later too, please.