Heater fan won't turn off.

the blower is silent.????????? yes, sounds matter !
ON HIGH TOO? (fan speed max)????
or makes normal sounds, but does not blow.
1 or the other.?

the blower if dead silent can be hot wired (blows now?) (costs zero to do)
or using any voltmeter made. measure for 12vdc on the 2 pin
to motor, fan on high. (costs $10 for tool at walfart)
if 12vdc there, (across the 2 pins) then the fan is bad.
of 0v, the controls are dead.
the fan on most cars. on high, bypass the fan speed resistor block.
what you dont have is the schematic,
its at 2 places (usa ,min)
alldata.com
and suzukipitstoppus. (real fsm book)

2000 GV, data, below.... it takes all of 10sec to look.
all answers, USA cars, as this is a USA forum.
i click HVAC for you.
as you can see the switch is grounded at red circle.
and with fan on high ground (0v) is applied to the motor low pin
and if the relay is hot, (2 fuse good) the output of relay b/w wire
will be at 12vdc, if not the relay is bad.(fuses good)
cant be more simple. same from 89-2000 after that things get harder, (controls) your car has a motor driven mode damper
that is why i asked the sounds questions. as it too can block the air flow. (with a perfectly running fan)

Not sure which fan you mean. Engine cooling fan is different from heat/air blower fan.

A couple of possibilities; air path blocked by debris (mouse nest, etc.), the sleeve-type phosphor-bronze fan bearings are clogged with wear particles, less likely but still possible is a failing blower switch, failing ground for the fan motor or an oxidized fuse or fuse holder.

A multimeter would be handy to isolate the source of the problem.

With your headlights on and shining on a vertical flat surface, try noticing if they dim very briefly when you quickly turn the blower on.
If not, then the fan isn't getting full current, if they do, then this would indicate a bearing problem with the fan.
Good luck-

Test the electrical circuits ! Manual HVAC or automatic HVAC ?
Do you know the difference ? Heater / A/C blower motor electrical control diffrent . Manual has resistors an a relay for different speeds , automatic has a blower motor control module .Free wiring diagrams here http://www.bbbind.com/free-tsb Enter vehicle info year , make , model and engine size . Under system click on HVAC ,then under subsystem HVAC controls will pop up . Click the search button , then the blue links . First off you need to know what system yours has , manual or automatic.
GMC Yukon HVAC Blower Motor Won Turn On
Blower Motor Problems Auto Repair Help

Check your blower motor resistor connection.Turn switch and fan on then wiggle the resistor pigtail fan should turn on if not replace resistor.These get to hot and usally melt the pigtail and loose their connection.

CHECK AC AND HEATER CONTROL FUSE. IF FUSE OKAY CHECK BLOWER SEE IF POWER GOING TO BLOWER MOTOR IF YES BLOWER MOTOR MORE LIKELY FAULTY.IF NO POWER GOING TO BLOWER MOTOR CHECK BLOWER MOTOR FUSE ANDRELAY.

your blower motor has gone bad and it over heats and shuts down

left to right...
1. empty
2. e flashers
3.horn, brake lights
4.clock, trunk light, inside light, radio
5. rad. cooling fan relay (AC only)
6. right side running lights
7. left side running lights
8. right high beam and indicator
9. left high beam and indicator
10. right low beam
11. left low beam
12. reverse,turn signal and inst panel
13. main and transfer fuel pumps, auxiliary air reg., ox sensor heater
14. license plate and glove box light
15. wipers
16. rear defogger
17. heater blower (no AC)
18. cig lighter
19. rad cooling fan (no AC)
20. Heater blower (AC)
21. rad cooling fan (AC only)
22. empty
23. Ox sensor, idle stabilizer,seat belt warning relay, (Digifant only, control unit, idle boost control, idle boost valve)
24. inst panel lights, heater control lights
25. reading lamps
26. empty
27. empty
28. empty

Hope this helps...;-)

what year model and make? it could be the blower module by the blower fan. just depends on year.

fan motor will not shut off