I have a 1999 Jeep Wrangler and the heater fan stopped working for all the fan speeds. The fuses are fine. How do you know if it is the blower resistor or the blower motor?

depend on HVAC options. (simple or the climate controls option)
but you never said,does it fail on all speeds.
that be first.
and the blower fuse. 2nd. if all fail.

fuses are always first on all electrics.

2005 wrangler (i have 08) and full docs TJ 03-06
but can get all docs..
the schematics are here for free, posted 100s of times... search?

http://www.morris4x4center.com/knowledge-base/index.htm?utm_source=cj#service
fuse 8 , blown (kills all speeds.)
if high works
the resistor block is bad. page 8w-42-2 in fsm.

Replace the blower motor resistance it controls the fan speeds.

Could be different problems.
The blower uses a resistor to regulate fan speed, the resistor could be faulty.
You would need to know if the radiator is full of coolant and if both heater hoses are getting hot. There may be a temp control valve in one heater hose that is not opening up to allow flow thru the heater core.

I think you could use this manual method instead.. My nephew used it to repair my car and it's perfectly fine now. Here's the website
he bought it from. www.reliable-store.com

It may be a relay problem. From the controls on the dash it should lead you to the components behind the dashboard. Check if the connections are OK. I am unsure if the relays are found there, but inspect the relay at that area or under the hood.

This is 100% the Blower (Fan) Motor Resistor located near the Blower Motor.
This is a very common problem with Chyrsler, Dodge, Jeep and Plymouth. The key symptom is the Fan only working on High.
This is very easy to access and replace.

Let me know if this helped....

Yes I would go with the switch, BUT, does it have a resistor bank? That is, how does it reduce the speed? Many systems use resistors to lower the speed. Burnt or bad connections can cause this as well.
You can test the blower motor by connecting direct power from a source like the cigarette lighter if you are handy.
Most of the time the lower speeds konk out but the high speed continues to work this is the resistor bank that goes out.

BJ
I'm using the comment section of the original posting to communicate with you.
Pat

blower motor resister has burnt out also check wiring going to your blower motor resistor these must have a good tight connection or they will burn if any sighns of being hot change the complete wiring pig tail to your blower resistor

check fuse first, every jeep ive had had the same problem ,its the fan speed resistor,most are located on the heater core /fan housing.NAPA 25.00 PLUS SHIPPING.