No Air Conditioning

[surfbeetle]

We have a 2016 2500 crew cab. My wife called today said the blower fan for the air conditioning stopped and won’t turn on no matter what she does. It was making some noise and this week. What should I troubleshoot? Do the fans actually fail on these? We’re at 84,000 miles. Thanks.

 

[Ltngdrvr]

Anything can fail.
Need a DVOM and check the motor for power.

 

[brucejohnson]

We have a 2016 2500 crew cab. My wife called today said the blower fan for the air conditioning stopped and won’t turn on no matter what she does. It was making some noise and this week. What should I troubleshoot? Do the fans actually fail on these? We’re at 84,000 miles. Thanks.

Have you tried all fan speed positions? I believe the high speed is a direct connection which bypasses the fan speed resistor.
ON EDIT: Woops. Speed reading all I saw was the 95 in your signature. Not sure on the newer truck. Often strange motor noises equals higher current draw and fuses doing fuse stuff.

 

[Timd32]

Tradesman should still have a resistor deal.

In the PDC you can check the fuse for a simple fix. But agree they don't just clear fuses, especially 40A fuses.

I'm always amazed at certain the automotive power system wattage amperage, figure I can run my whole house (less AC) on a #10 wire 40A gen circuit.

F13
40 Amp Green
Blower Motor

There is a really long procedure for this issue under blower noise. Will if there is a shorter version.

 

[AH64ID]

I'm always amazed at the automotive power system amperage, figure I can run my whole house (less AC) on a 40A gen circuit.

Amps aren’t universal, watts are.

40A at 14V is 560W
40A at 120V is 4800W

Basically the higher the voltage the fewer the amps that are needed to do the same work.

 

[Ozymandias]

Yep, Watts are work.
Amps mean not a lot.

Do they really still use Resistors? Sounds weird on a almost new vehicle.

 

[Timd32]

It's only a .5 hr labor, .4 hr warranty labor to replace the unit. So the whole noise procedure is pretty useless IMO.

So might be worth pulling the unit, if fuse is good, and realy checks out.

Since it was making noise I would suspect the assembly, but there is a relay along with that fuse above, I'll toss that on the bottom.


Found this description:

WARNING:
Disable the airbag system before attempting any steering wheel, steering column or instrument panel component diagnosis or service. Disconnect and isolate the negative battery (ground) cable and wait two minutes for the airbag system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the airbag system. Failure to follow these instructions may result in accidental airbag deployment and possible serious or fatal injury.

On the Manual Temperature Control (MTC) heating-A/C system, blower motor speed is controlled by regulating the path to ground through the blower control switch and the blower motor resistor. With the Automatic Temperature Control (ATC) heating-A/C system, blower motor speed is controlled by an electronic blower motor power module, which uses a pulse width modulated input from the A/C-heater control and a feedback signal from the blower motor to regulate the blower motor ground path. On both systems, the blower motor will operate whenever the ignition switch is in RUN and the blower motor control is in any position except Off. The blower motor receives battery current through the Power Distribution Center (PDC) whenever the ignition switch is in RUN.

The blower motor can be accessed for service from underneath the instrument panel.

NOTE:

The blower motor is supplied with a 12V feed from the BCM whenever the ignition switch is in RUN. Due to an open circuit condition within the blower motor control switch the BCM is UNABLE to detect an OPEN circuit for the blower motor.

The blower motor control system is diagnosed using a scan tool (Refer to 28 - DTC-Based Diagnostics/HVAC - Standard Procedure) .

The blower motor and blower motor wheel are factory balanced as an assembly and cannot be adjusted or repaired and must be replaced if inoperative or damaged.

NOTE:

The blower motor is located on the passenger side of the vehicle under the instrument panel. The blower motor can be removed from the vehicle without having to remove the HVAC housing assembly.

1. Disconnect and isolate the negative battery cable.
2. HVAC wire harness lead (3) from the blower motor (2).
3. Remove the three screws (1) that secure the blower motor to the bottom of the HVAC housing (4) and remove the blower motor.

Good luck with your fix.

 

[Timd32]

Yep, Watts are work.
Amps mean not a lot.

Do they really still use Resistors? Sounds weird on a almost new vehicle.

Yep sure do on the Manual control trucks.

 

[Timd32]

Amps aren’t universal, watts are.

I can offer Amps are very universal at times..

"Hey kid go grab me a 560w fuse"

I do appreciate the reply and breakdown so JK. All in good fun. It can't all be I have this issue give the fix and scram see you when I have the next problem.

Maybe it's too simple thinking but I still think overall these things are just pretty cool how much work gets done. With all these circuits and how much a #10 wire can and can't do at times due to that's just the way it works.

 

[Topzide]

Very common failure of a blower motor is VERMIN! They get in the blower box and the squirrel cage fan makes a nice nesting spot! Once their in, they get things being blown around and debris can wrap around the resistor and cause failure. Ask me how I know! Changed several components of each over the years! Living in the woods can get costly. Had to carpet bomb under the hood of the truck due to vermin chewing the battery cover! took three nights to catch the offender but got'em! If debris is found, break out the shop vac and after vacuuming out, put hose in exhaust port and then blow through opening. Open all windows, wear a dust mask! You can also blow through vents down into box also. Vac won't produce the pressure of an air line, just volume to push everything out. Good luck. Not a bad job as long as you don't need to evict anything!

 

[AH64ID]

I can offer Amps are very universal at times..

"Hey kid go grab me a 560w fuse"

I do appreciate the reply and breakdown so JK. All in good fun. It can't all be I have this issue give the fix and scram see you when I have the next problem.

Maybe it's too simple thinking but I still think overall these things are just pretty cool how much work gets done. With all these circuits and how much a #10 wire can and can't do at times due to that's just the way it works.

But fuses aren’t universal either. Too many different styles, but I get your point. That’s because a 10ga wire can’t do the same work in different voltage applications, as it can only transmit the same number of amps regardless of the voltage. So 10ga should always have no more than a 30A fuse/breaker on it, for any voltage.


A 10ga wire can do around 10X the work on household voltage vs automotive voltage. Voltage is key to the amount of work that can be done. This is one of the reasons why line voltage is to transformers is generally 7200-3K, and transmission voltage can be anywhere from 100K-800K.

 

[Ozymandias]

Interesting they did the short cut with the tradesman, so the blower always takes the full current of 40 Amps, no matter at which speed it runs.
Poor man's solution.

 

[Timd32]

Wouldn't varying the resistance change the overall wattage used up?

From the book here is the overall operation.

Value engineered for sure. I have a Tradesman and it's fine for what I need. Not so great for resale value, but gets the job done.



OPERATION

The blower motor resistor is connected to the vehicle electrical system through a dedicated wire lead and connector of the HVAC wire harness. The blower motor resistor has multiple resistor wires, each of which will reduce the current flow through the blower motor to change the blower motor speed.

The blower motor control for the heating-A/C system directs the ground path for the blower motor through the correct resistor wire to obtain the selected speed. With the blower motor control in the lowest speed position, the ground path for the blower motor is applied through all of the resistor wires. Each higher speed selected with the blower motor control applies the blower motor ground path through fewer of the resistor wires, increasing the blower motor speed.

The blower motor resistor cannot be adjusted or repaired and must be replaced if inoperative or damaged

 

[lpennock]

Ohms law.
Voltage = Current x resistance (E=IR)
Power = Voltage x Current (P=EI). Substitution with from the above yields P=E^2 /R.
So Timid32 is correct that as resistance is increased, the Power consumed is reduced.

 

[Ozymandias]

Ohms law.
Voltage = Current x resistance (E=IR)
Power = Voltage x Current (P=EI). Substitution with from the above yields P=E^2 /R.
So Timid32 is correct that as resistance is increased, the Power consumed is reduced.

I'm not sure about that, it's a Resistor.
It changes current into heat and therefore the blower runs at a slower pace.
From what I measured in the past it flows almost the same amps no matter in which speed setting it is.
But maybe I'm wrong, I'm not an electrician.

 

[brucejohnson]

I'm not sure about that, it's a Resistor.
It changes current into heat and therefore the blower runs at a slower pace.
From what I measured in the past it flows almost the same amps no matter in which speed setting it is.
But maybe I'm wrong, I'm not an electrician.

The current is limited by total resistance of the circuit. Voltage being constant, it is divided over the numerous resistances of the circuit (wires, connections, loads, etc.) which determines the total circuit current. The 40 amps is a limit placed on the circuit by design to protect the circuit from damage if an issue arises that would exceed safe parameters. In the case of the blower motor, the current would be at its maximum when the fan switch is in the high position. The full voltage ia applied to the motor windings which have very little resistance. Maximum current flows, which should be a percentage lower than the 40 amps of the protective fuse. By inserting the voltage regulation function of the resistor block resistors, each switch position changes the total resistance of the circuit and varies the speed, greater resistance switched into the circuit equals slower speed. The motor is in essence an electro-magnet where the increase in current caused by a reduction in circuit total resistance which allows the speed to increase. (More voltage dropped across motor = more current flow = greater magnetic force = greater speed).
If you slow the motor down due to bad bushings/bearings, or some critter or foreign object hanging up on the fan cage, the current will increase across the stator and rotor windings as they are not spinning at speed enough to allow the coils to cool down during operation. They are designed for short spurts of energy and will act like an over loaded transformer if the rotor and stator windings are not moving fast enough to reduce the current which generates heat quickly. A bad/blown fan resistor may be due to the excess current caused by the motor bushings binding sufficiently to cause slow, incremental increases in total circuit current not yet to the point of blowing the fuse, but just enough to "burn out" the resistor block resistor element.

 

[Timd32]

Very common failure of a blower motor is VERMIN

I think something is not right in the box for sure.

Should be a real simple pull it out and take a look.

I just found brand new Pinkie mice at the bottom of truck on Friday, damn thing was living in the air box, luckily caught it pretty early they only got a little of the battery cover.

But for sure, pop the motor out and take a look. Fastest thing going if able too.

 

[surfbeetle]

Thank you all for the replies. Yesterday I checked all of the fuses. All were good. I did swap the fuel heater relay with the blower relay, it didn't change anything so I swapped them back. Then I checked the voltage at the fan's harness plug, it was good. I then decided to drop the fan out of the housing. I connected it up to my battery charger and it spun up. At this point, I reinstalled the fan and buttoned everything back up. It's working now and my wife is happy. From one of the videos I watched, it made it seem that because this model year has the resistor built into the fan, there's no changing just the resistor like previous years had. Also, it said that even if the fan starts working again, it's not long for this world and I would eventually have to replace it. Does this match anyone's experiences? We are just now out of warranty on things like this (I did just purchase a basic powertrain warranty however) so this will be on my dime. I priced the fan at $170 from Steve White Motors. Thanks again

 

[brucejohnson]

Thank you all for the replies. Yesterday I checked all of the fuses. All were good. I did swap the fuel heater relay with the blower relay, it didn't change anything so I swapped them back. Then I checked the voltage at the fan's harness plug, it was good. I then decided to drop the fan out of the housing. I connected it up to my battery charger and it spun up. At this point, I reinstalled the fan and buttoned everything back up. It's working now and my wife is happy. From one of the videos I watched, it made it seem that because this model year has the resistor built into the fan, there's no changing just the resistor like previous years had. Also, it said that even if the fan starts working again, it's not long for this world and I would eventually have to replace it. Does this match anyone's experiences? We are just now out of warranty on things like this (I did just purchase a basic powertrain warranty however) so this will be on my dime. I priced the fan at $170 from Steve White Motors. Thanks again

Is that for the higher end HVAC systems with the dual zone/automatic features?
I find MoPar part number 68048900AA shows for some 2016 Rams, like the Tradesman.
Put your VIN in the search tool to see if it fits.
68048900AA - Genuine Mopar Resistor-Blower Motor (moparpartsgiant.com)

Amazon.com: Chrysler Genuine 68048900AA Electrical Blower Motor Resistor: Automotive

 

[JR]

. I have a Tradesman and it's fine for what I need. Not so great for resale value, but gets the job done

Resale value is relative to initial cost. When the delta between low and high (new) is $25k you can afford to take a hit on the back end. Depending on length of ownership and repairs out of warranty the argument could well be made the Tradesman would hold the higher value. These trucks are expensive to maintain post warranty and despite buying into the so called upper trim levels, components are generally low end looking at the long term value.