So recently my resistor for my blower motor keeps blowing out. Initially I replaced the old one and put a new one in, and it didn’t blow but the pig tail melted. So I did some research and found out it might be the blower motor pulling to many amps, so I replaced the blower motor itself with one I pulled from a scrap yard, spliced in a new pig tail and put the new resistor that came with it in and now the resistor is smoking on the lowest fan setting.
Would anyone know what’s happening? Seems like for some reason the amps flowing through are still way to high, but have replaced basically every component other than the entire HVAC harness behind the dash.
The resistors were new, and the blower motor was actually replaced with a dealer sold part in the Torrent I pulled it from. The manufacture date was newer than the car itself.
I am pretty hesitant to go spend more cash on brand new parts if it’s just going to be the same issue as with the slightly older parts.
The motor or airflow may have a restriction problem that is causing high current flow inside the motor. It would be nice to know how much current is needed by the motor while it is removed from the housing and compare that to the current needed while it is mounted inside the housing. Measuring the current at the fuse holder is an easy way to check the current. I would guess a normal current would be around 6 amps at full speed.
The resistor will usually get hotter on the lowest fan speeds, compared to higher fan speeds. The power available on a DC motor arrangement such as this is divided between the resistor and the motor, and at lower fan speeds the motor obviously uses less power, so the resister has to dissipate more power.
The problem most likely is the blower motor is using more current than it is supposed to be. Either the motor is defective, or the fan-cage it spins isn’t turning freely. It’s a pretty common thing here to get reports of leaves and twigs interfering with the blower cage, especially true on older cars. Remove the motor and inspect the cage area, making sure the cage isn’t being obstructed by anything. If that turns out to be the problem it’s helpful to vacuum the air inlet area under the windshield to keep leaves and twigs from getting sucked into the blower cage. I do that on every oil and filter change.
I just had another thought about this problem. I wonder if the air ducting is getting blocked somehow (a mouse nest possibly). That may cause higher current flow in the motor. It would also keep the resistor pack from getting proper air flow over it to cool the resistor pack down like it is designed to be.
Most blower designs I have seen in automotive applications are centrifugal fans. They draw LESS current as the airflow is blocked or decreases. The fan speed will increase due to the lower loading on the fan. Look at a vacuum cleaner as an example. The rpms go up when you block the inlet (or outlet) and it doesn’t blow the fuse- it actually draws less current when blocked as the fan isn’t doing any work.
My question would be, how did the OP observe the smoke? The resistor pack needs to be in the airstream the fan creates to keep it cool. The lower the selected fan speed, the more chance of damaging the resistors from not being cooled by convection from the fan, when the fan is doing work. The lower speed setting drops more power across the ballast. If you look at the resistor pack, you may notice larger wattage resistors for the lower speeds. The highest fan speed uses direct power through a relay in many designs…
I had the resistor pack pulled from the dash to see if the high setting would again blow the resistor. Which it did after running for roughly 5 seconds.
I replaced the fan though with another one so I am not sure that it is a fan issue unless there is something that it’s getting caught on inside the fan housing. I would say that’s not very likely though because the fan was blowing very strong until the resistor blew. Going to go pick up another resistor and fan from the dealership tonight though and do what one of the other posters mentioned and get a parts warranty just in case I install it and it blows out like the older parts. I’ll het under though and check the air box for any obstructions.
If you have a DVM, you could measure full speed current draw from the motor to verify it’s within specs. The next thing I would be doing is inspecting the supply wiring, looking for damaged wiring or connectors feeding the motor. Any compromised wires or connectors can starve the motor and cause it to draw more current than it normally would. If you test the system out of its normal environment, make sure the resistor pack is positioned in the airflow to limit the potential for damage due to overheating…
Alright I’ll take a look underneath and see what I can do. I bought this car a year ago and I know the last person that owned it had the same issues. The old blower motor had scrap yard paint pen all over it. Just priced out a new motor though through the dealership and they are charging $400.00 for a new blower motor. So I want to make sure I rule everything out before biting that bullet.
Will try to pull the whole HVAC harness and do an inspection.
You stated that the resistor pack was damaged while the fan speed was on high. That seems strange to me because I believe the resistors are not in the circuit when the fan is on the high setting. If this is the case I have to wonder if the resistors are wired up correctly. They should be in series with the motor leads unless the high speed selection is made and they are bypassed from the circuit…
