Fan only works sometimes

[chips2481]

I have a 90 ranger and I have a problem where the fan will only work sometimes. Sometimes it starts up and runs at full speed and sometimes it will run slower and then work it's way up to full speed and then later it will just shut off. Most of the time it just won't turn on at all. I am thinking maybe there is a relay box for it somewhere. Anyone have any other ideas?

 

[Jason94sport]

Blower motor relay in the under hood fuse box.
Or
Blower motor resistor on the side of the blower motor case in the engine bay.
Or
Bad blower motor.

 

[gijoecam]

If it was the relay, it wouldn't start slow. The resistors don't typically change resistance (which controls the speed of the fan). My money's on the blower motor itself.

Since you'll have it out anyways, replace the resistor for another $17. You'll need to do it sooner or later anyways.

-Joe

 

[chips2481]

is there any way to hook power from the battery right up to the blower motor to check to see if it is good?

 

[gijoecam]

Sure. Just use a pair of alligator clips to the appropriate connector. If it runs, it's not the blower.

Here's another question: Does it run on high? When set to high, the high speed relay bypasses the resistors. If it works that way, I'd be looking at the resistor pack.

 

[rwenzing]

Also check the plug connector on the blower resistor. It has a tendency to corrode and increase resistance. This can cause reduced speeds or for certain speed settings to drop out.

 

[chips2481]

I---I
--I--

Doesn't the plug look like the example above? Would the bottom be negative and either of the top be positive? Would it hurt the motor to mix and match the connections until I find the right one?

If I turn it to high it will not run if the other settings won't work.

I checked the main plug that goes into the blower motor and it looked clean, I will check for any other plugs that might connect to the main plug.

 

[rwenzing]

The resistor connector should have 4 wires. As far as I know, the blower motor itself only has a 2 wire plug but I don't have a 90 here to look at.

 

[chips2481]

I will take some pictures tomorrow. thanks

 

[Potomac30]

While you're at it, be sure to vacuum all the leaves and pine needles etc. out of the housing that the resistor is attached to. I thought that I had an electrical fire in my 93 explorer Wednesday, it turns out that the resistor set the leaves on fire - which filled the cabin with smoke. Hats off to this forum for an internet diagnosis. The blower motor comes off by removing three 8mm screws; remove the air filter box first. This will allow you better access to get all the trash out away from the resistor (AC model).

 

[chips2481]

alright thanks. Sorry I forgot to take the pictures I will take them tomorrow.

 

[cjones101812]

the blower motor is ground switched.

at the blower motor you should have power (12v) at the BR/O wire with key ON.

turn blower motor (fan) on high, Key ON, A/C ON. connect voltmeter between BR/O wire and O/BK wire. should have 12v. if 12v then blower motor is bad. if you do NOT have 12v then check for ground at switch DB/W wire.

 

[chips2481]

the blower motor is ground switched.

at the blower motor you should have power (12v) at the BR/O wire with key ON.

turn blower motor (fan) on high, Key ON, A/C ON. connect voltmeter between BR/O wire and O/BK wire. should have 12v. if 12v then blower motor is bad. if you do NOT have 12v then check for ground at switch DB/W wire.

You say I should have 12v and if it is 12v the motor is bad. Do you mean if it is not 12v the motor is bad? Should I have it plugged in when I test it or unplug it and test from the plug?

 

[cjones101812]

You say I should have 12v and if it is 12v the motor is bad. Do you mean if it is not 12v the motor is bad? Should I have it plugged in when I test it or unplug it and test from the plug?

it should be unplugged when you test it.

you should have 12v at the connector. POS lead on the BR/O wire and NEG lead on the O/BK wire. if you have 12v at the connector then the motor is BAD. [if you have power (POS and NEG) going to it and it doesn't work then it is bad].

 

[chips2481]

cool, thanks. I will try that then reply back probably tonight