Heating System I own a 2003 Nissan Sentra. The blower works, but I only get heat once the vehicle reaches high speeds around 60-65mph. Please help.

If you have a fan that has different speed settings (1234, or low med high etc) and the only one that works is high - then the blower resistor pack has failed. If you have a climate control unit (where you just pick a temp you want) then the fan is controlled by the heating system and it sets fan speed. If you have climate control style try lowering the temp to a lower setting (current temp in vehicle) and see if fan slows down. If not then climate control unit or fan resistor bad. If dial type and you get nothing on lower settings (only high works like mentioned above) you need to change blower resistor. It is located under dash near the fan itself. Look for small unit bolted in duct near fan with wire plug going to it.

Its faulty blower motor resistor. The low and medium speed on blower motor is controlled by resistor and its actual speed is high. So because resistor is not working, blower motors actual speed which is high is working.

It can be faulty blower motor or faulty blower motor resistor. Get the blower motor inspected. If it's faulty it has to be replaced.

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For blower motor testing and replacing, check the link below: ----

Blower motor Testing/replacing for all vehicles?

http://repairhelpcenter.blogspot.in/2012/02/blower-motor-replacing-for-all-vehicles.html

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These will help.

Thanks.

If the engine has overheated, chances are pretty good that you now have a warped or cracked cylinder head and a blown head gasket. Those engines are very unforgiving when it comes to being overheated.

Fan resister circute/switch needs to be replaced. Not expensive. Buy from dealer.

Hi Adam,sounds like your blower motor resistor is bad,it controls your blower motor speed.Here's a link on how to replace,read the beginning and it will explain how the system works,as it says,their a different types for your vehicle so remove and take to Autozone and match it up with a new one. Repair Guides Heating And Air Conditioning Blower Motor AutoZone com Here's a link to some new one's. Blower Motor Resistor

you need blower motor resistor

First of try to understand exactly what part you mention exactly how they work or function

1. please place a new low speed relay as it try to make out thermal heating cool at it's initial 1st stage level of heating so that the temperature remain maintain if thus it reaches the second level of heating then the high speed relay act at that time & the speed of radiator fan increase to get thermal heating in control.
2. the thermostat regulate the heating temperature of the engine it senses the temperature & signal to the relay the relay then react according to the temperature level of engine at low heating it operate the low speed relay & high temperature it signal to high speed relay so the engine temperature does not rise to extended level of heating or overheating.
3. see for thermostat valve is failure if that so replace it new sometime most of the mechanic change it or cancel it so that the temperature does not rise as this thermostat help engine maintain it's ideal temperature which is required by the engine for regular or good working even at extreme climatic condition.
4. Do check for every tensioner or Ideal Bearing as far consider on the No. of miles or Km the vehicle has run according to us the tensioner or ideal bearing are suppose to be replace at an interval of 30000 to 35000 Km. but this replacement include both Engine timing belt & tensioner & ideal tensioner bearing.
5. A water pump flow depend on the tension of the drive belt some vehicle come with water pump which drive on inner timing belt tension & some on the fan belt or external tension belt of engine.

for further more FAQ do send in or place your problem we will sort it out till then have a safe drive & happy motoring from siddhanth.....!

Hi.....
On your Vehicle the problem for the FAN speed is NOT the FAN switch.
99.9 % of this problem on cars is the BLOWER MOTOR RESISTOR.
The blower motor resistor give the speed to the Fan.
But on High speed the switch make a By pass of the switch using a Relay for the high speed.
The Blower motor resistor, is located Beside of the Blower motor On the passanger compartment.

If you replace the blower motor resistor you have 99.9% of this will solve your problem.

I'm a Mechanic.

I hope this help on your problem.
Thank you for use fixya...

does the car overheat at idle or travelling down the road? if the thermostat was not changed, thats first step. checking it is replacing it. possibly air-bound. then i would suspect a headgasket problem.