99 Ram Van 1500 - repeated blower resistor failure:
The first resistor(A) pack I replaced is old (possibly original), with a bit of grime and a tiny bit of rust on the cage.
The first replacement(B) was in September before I ever used the heater.
I did run the A/C all summer, and not always only on HIGH but on every speed, without fail.
No pins are burnt, I didn't find anything abnormal with the switch. I will add some dialectric grease.
The replacement resistor(B) pack crapped out on Jan 15, 2012. Luckily I got the Autozone lifetime warrenty part.
But today is only February 10, and the last resistor(C) pack has also kicked the bucket, as we finally get some snow and cold weather rolling in.
I will get another new one today, but this sort of cycle is annoying.
I'd like to:
1) know what amperage the motor should be pulling at the three speeds?
2) a source for a compatible resetable thermofuse? Or self-resetting even?

 

The fan itself is drawing to much ampreage and causing the resistor pack to burn out. The fan needs replacement.

 

Yes, too much blower motor draw or the aftermarket resistor is simply inferior to the OEM one.

 

I don't know if this is appropriate but I'd like to jump in here if I may. I have a 92 B250 and when I run the fan on high the RED A1 circuit wire from the ignition switch gets very hot. More so when the AC is running. The A1 12 RD goes through the number 49 position in the bulkhead connector to the engine compartment then is spliced in at the AO splice point with an A1 20 OR wire and fusible link then to the charging system. If I leave the van running with AC on and fan on high the fusible link fails. Since I haven't been able to find the replacement FL, I put a 20 gauge wire in and it will eventually melt and fail. By running the fan on any speed other than high, keeping the AC off the temperature doesn't get high enough to fail the wire. I've thought of putting in a replaceable fuse but I'm not sure what size and that doesn't really solve the problem.
There is just too much current draw but I don't know why. Blower motor? Fan switch (I put in new one)? HVAC vacuum control switch (I replaced it)? AC resister? Any ideas of what to do next?

 

FWIW heat within an eletrical circuit is only caused by 2 things...
too small of wire for the amperage, or
too much resistance within the circuit.

I have only been here for a couple of months, but have read several posts about eletrical problems. I have noticed several ground points within my van. I would check these if I would ever have similar problems. Also a weak battery and or alt. can do these same things.

Good luck out there.

 

@ funair02..... FWIW? can you tell me what this means? I agree completely with you about the wire/resistance and so I was very confused when I saw that the AO splice point is at the 6 gauge wire going from the positive battery terminal to the charging system with a 20 gauge wire connected to it and then splice into the 12 gauge wire that goes to the ignition switch.

There is/was a fusible link on the 20 gauge so my thinking is that the rest of the circuit should only have ever been subjected to a amperage level consistent with the smallest/weakest part of the circuit.

Obviously, in my case the load is exceeding the "weakest link in the chain" capacity.

Still trying to find someone who may have had this same problem or can identify the source of this "overload" condition.

thanks,
mike

 

FWIW = For What Its Worth.
I haven't had any more trouble with the Blower Motor Resistor since the replacement last winter.
I did have an unrelated AC problem. As the summer got hot, I felt the AC wasn't very cool. I started to ad a bit of R134, and saw fluid spitting back out when I pulled the connector off the port. The valve core was very loose. Hmm, AC was ice cold last summer, and ONLY the people at a oil change chain have been under the hood. The system is tight and full now

 

If you are experiencing repeated resistor pack failure the issue is not neccessarily the blower motor. Assuming the blower starts instantly when switched on and spins freely without unusual noises you should be looking for a blockage in airflow. The resistor pack incorporates a thermal fuse. When the airflow is not sufficient, then the thermal fuse will fail.

Airflow from the dash vents on med high or high should be very strong when working properly. On high you should be able to feel air flow in the second seating row.

To check for obstructions and inspect the fan you can either remove the blower motor or remove the right fender. Set the climate control to a fresh air selection to open the fresh air door. I pulled a large plastic bag and a lot of leaves out of mine. Assuming this ductwork is clear, next open the heater/evaporator box a little and inspect the face of the evaporator for debris. You can also peer inside through the hole for the resister pack. All airflow: heat, fresh air, ac, everything! must pass through the evaporator. If it's clogged the system will not have adequate airflow and the thermal fuse in the resistor pack will burn up.

 

While on the topic of Blower Motor Resistors...in cases with a Rear Air Blower, rear air blower switch , and evap in rear of van....Does it HAVE to have a blower resistor back there somewhere? I have a newly purchased conversion, and cannot locate a resistor pack back there anywhere...Evap coil is shiney clean like it never had airflow. It is possible the rear blower never worked....because original installation ommitted the resistor pack??? ((The front blower motor switch blows the fuse when turned on is what started me on the path. Rear blower motor is new, relays are checked and good (new also)))

 

I don't have the rear AC/heater but according to the manual:

Reach under the front of the unit to unplug the wiring harness connector to the resistor pack
Remove the horizontal duct
Reach inside the duct opening and remove the resistor pack with pliers ( or a small hand)