The blower motor test, on the 3.0L Nissan Pathfinder, D21, and Pick Up, is a very easy test.
In this tutorial I'll explain the two tests that you need to perform to find out if the blower motor is bad or not.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Cómo Probar El Motor Del Soplador (1990-1995 3.0L Pathfinder y Pick Up) (at: autotecnico-online.com).
NOTE: You can find the blower motor circuit diagram here: Blower Motor Circuit Diagram (1990-1995 Nissan Pathfinder And Pick Up).
BLOWER RESISTOR ASSEMBLY TEST: You can find the blower motor resistor assembly test here: How To Test The Blower Resistor (1990-1995 3.0L Nissan Pathfinder And Pick Up).
APPLIES TO: This tutorial applies to the following vehicles:
- 3.0L V6 Nissan D21: 1990, 1991, 1992, 1993.
- 3.0L V6 Nissan Pathfinder: 1990, 1991, 1992, 1993, 1994, 1995.
- 3.0L V6 Nissan Pickup: 1994, 1995.
Blower Motor Basics
The blower motor is a simple 2-wire component. As such it needs battery power and Ground to function.
On the 1990-1994 Nissan Pathfinder (D21 and Pick Up) this battery power comes from fuse D in the dash fuse box (see illustration 1 of 2 above).
On the 1995 Nissan Pathfinder (Pick Up) this battery power comes from the blower relay (see illustration 2 of 2).
Ground is provided by the blower control switch located in the AC Heater Control Panel.
To see how battery power and Ground are routed thru' the blower motor, blower resistor, and blower switch circuits; check out the circuit diagram here: Blower Motor Circuit Diagram (1990-1995 Nissan Pathfinder And Pick Up).
Now, when the blower motor fails on your 3.0L Nissan Pathfinder (D21 or Pick Up) you're gonna' see one of the following symptoms:
- The blower motor will stop working completely.
- The blower motor will run, but run with a lot of bearing noise.
A blower motor with worn out bearings will use an extreme amount of current (from the mechanical resistance to the motor rotation). This high amperage draw can overheat and destroy the blower motor resistor.
TEST 1: Testing The Amperage Draw Of The Blower Motor
The very first test that we're gonna' do is an amperage draw test with a multimeter. This is a very easy test and it will let us know if the blower motor uses too much current.
The blower motor should use less than 15 Amps. If it's using more than 15 Amps then you can consider the blower motor bad and that it needs to be replaced.
NOTE: If you don't have a multimeter and need to buy one, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
Let's get started:
Disconnect the blower motor from its electrical connector.
Place your multimeter in Ohms mode.
Measure the resistance of the blower motor with your multimeter.
NOTE: This test is done on the connector of the blower motor itself. The connector on the blower motor has male spade terminals.
Divide 12.5 by the resistance value you got in step 3 (12.5 is the battery voltage). The result of this calculation is the amount of amperage the blower motor is using.
To be a little more specific: Let's say that the resistance reading was .4 Ohms. This is what the math would look like: 12.5 ÷ .4 = 31.25 and this would translate to 31.25 Amps.
Let's take a look at your amperage draw test result:
CASE 1: The amperage draw is under 15 Amps. This is the correct and expected test result and let's you know that the blower motor amperage draw is within specification.
The next step is to manually apply power and ground to the blower motor itself. For this test go to: TEST 2: Applying Power And Ground To The Blower Motor.
CASE 2: The amperage draw is 15 Amps or more. This test result tells you that the blower motor, on your 3.0L Nissan Pathfinder (D21 Or Pick Up) is defective and needs to be replaced.
Even if the blower motor runs, it's using way too much current. This excessive current draw will blow the blower motor fuse and/or fry the blower motor resistor.