Brushes collapsed on fan motor replaced fan now motor runs without ignition on

in review
the fan speed resistor is new
you bench tested the blower motor
12 volts test ..only runs it at full speed
if cabin filer want changed the blower motor would run hotter

could be the motor brushes or bush/motor bearing when slowed
you might want to inspect the brushes and clean the dust out of the motor
if no better
does that have climate control ?
might be the fan switch itself or the earth isnt so good

OK, you have addressed the first possibility. There are a few more, each progressively more expensive to fix. First, are the radiator electric cooling fans operating? If you find the vehicle runs ok on the highway, but overheats around town in stop-and-go traffic, it could be that the fans are not running. Quick check for the fans - with the ignition on (the engine doesn't need to be running), move the cooling control to the A/C position. If the fans come on, they are good, but you could still have a fan-related cooling problem. If the fans don't work, you have a problem. If the fans worked, the car runs fine at highway speed but not in town, then suspect the coolant sensor that engages the fans. If the fans work and the car overheats in all conditions, then a system blockage is possible. Blockages occur usually one of two ways: Radiator rust/corrosion, and collapsed radiator hoses. Radiator corrosion will require radiator replacement; if it is blocked badly enough to overheat, flushing it is a waste of effort, and could cause more problems with all the **** you circulate into the engine. If the system is low on water (air in system) it can rise to the top radiator hose and cause it to collapse partially or fully, restricting flow. Some engines have water jackets that extend higher than the radiator cap, so they can trap air. These cars have bleeder ports at these locations to remove to trapped air. Check to see if that is the problem.

It is possible that the radiator fan bearings are dry and causing extra drag on the motor and blowing the fuse. Without the fan operating you will experience overheating. The bearings are usually a plain bronze bush type and the lubrication dries out eventually. You could try removing the fan assembly and carefully dismantling the motor. Once apart check for worn out brushes and if they are OK, then soak the bearings in engine oil and reassemble. The bearings are self aligning but once it is running after the motor has been put back together, give the motor body a light tap on the sides near the bearings to make sure the rotor is running free. If this all sounds too difficult, you may be able to get a replacement fan assembly from a salvage yard.

Is the cooling fan running? If so, drain the radiator with the heater control set to hot. Install a new thermostat, and fill the system with a 50/50 mix of antifreeze and distilled water. Bleed all air from the system by using bleeder screws if equipped, and by starting the engine with the radiator cap off radiator full. Watch for escaping air bubbles and keep the radiator full. When you see no more air escaping put the cap back on. If the fan is not running then that is your problem. Turn the A/C on and the fan should run continuously. If it does not the fan motor is more than likely bad. Check the fuse for the fan. If it is good, Apply 12 volts directly to the fan motor to check it. If it runs then replace the thermal relay.

The brushes get worn down on these motors. Your "give it a boost" description leads me to believe this is your problem. You can replace the brushes without buying new motors if you find a place to buy them.

Check the fan itself, could be worn brushes hence the motor will not turn. Fan is under the cubby hole

If you are in a hot climate and use the AC year round like I do, it is possible that the fan motor itself is worn out. My 2003 had this occur and it progressed to idling problems before it was resolved.

The motor has carbon brushes inside it which do wear out with use. The brushes are staggered (I dis-assembled mine as a post-mortem). At idle, both brushes are in use. At highway speed only one brush is in use. Directly attaching the battery gave it normal voltage - but much more current than normal. That is why it worked.

My solution is to replace the fan motor with a BRAND NEW one. A salvage part would work, but you run the risk of not knowing how worn its brushes are. New fans are available w/o the shroud and fan blade at many parts stores. Mine took a week on special order and cost around $150 for one with a lifetime warranty. Pretty straightforward to swap out - just make sure the wiring connector is correct before you disassemble the shroud. The replacement motor had the wiring located slightly different, but I was able to easily drill the plastic shroud and re-route the path of the wires.

could be a carbon brush issue of the fan. try to wiggle the wire that goes to the fan. if the fan runs, then it is a carbon brush problem. you need to replace the carbon brush of the motor.

tnx 4 using fixya,

drcool

could be a motor brush problem. try to tap the motor slightly and see if the motor would run. also try to wiggle the wire and see also if the motor would run.
if the motor will run, pull the fan down and replace the brushes of the motor.

tnx 4using fixya,

drcool

Those fan motors are very prone to wear the carbon brushes very early. They last 4-5 years tops.
After checking the fuse and relay of the motor fan. The culprit should be the motor brushes.
Replace both fan motors.