blower motor quits, works again, and quits

[fabianoliver]

Hello all, my blower motor ( 1994 XLT) stops working for one day a month ago.
Next day, it starts working ok, until today. A rainy day.
I read here that blower motor problems possibly are related to a fuse or relay .
My question is, can a relay works sometimes and other days not? or once bad, it stops working forever?
Can someone has a picture were is located the blower motor relay and how it looks?, and the fuse?
Another ideas ? bad electrical contact maybe?

Thanks all for your comments

 

[96AWD5.LOL]

Any chance you can check for voltage at the connector when its not working? It won't tell you whether it can take a load but would be a start. To check for a load you can use halogen bulb, jump the pos and neg and see if it will light up. Make sure the fan is on high.

 

[J_C]

I assume it does not work on all speeds including high?

Relays that degrade, don't tend to completely fail then come back to working well again, but the vehicle has a lot of years on it, if all else fails, certainly try swapping that relay with another known working relay. Take the fuse out, examine the contacts for corrosion and of course that it isn't blown.

There's probably a topic in this forum that details which relay box and position that relay is in, and the owner's manual should show the fuse location. The relay box is "probably" around or under the battery or air filter box if not in the main power distribution box under-hood. There's probably nothing to see visually to indicate the relay is bad, inside a black plastic housing, unless the contacts or relay box contacts are corroded.

Checking voltage at the fan connector is definitely something to do, voltage on one pin and chassis ground should be 12V or more, and the other pin should have low resistance to chassis ground.

If it's getting power, plug back into the fan and measure if voltage is drooping a lot. This could indicate fuse corrosion, relay contact corrosion, or a seized motor. The motor may have a bad spot on the commutator or brushes shot, or chewed up bearings.

Intermittent faults can be a pain in that you may have to wait till it fails again, to make the diagnosis. I'm attaching a wiring diagram from a 2nd gen explorer so ignore the fuse designations, connector pin #s, and wire colors, but it does still indicate the (probable) topology of the circuit which could help to trace where power stops with a multimeter.

 

[Turdle]

Could just be bad connections in the socket where the relay plugs in. Check that for heat damage.

 

[Motorhogman]

Had a similar issue years ago with my 00 Sport. Turned out the blower motor resistor was corroded.

 

[fabianoliver]

Thanks all for your replies.
Today , in the morning it worked and in the afternoon, not.
I'll follow your suggestions, and with the haynes and owner manual i'll locate the fuse, relay and resistor.
I keep in touch, this weekend, i guess i'll be able to put my hands on.
Thanks JC for your wiring diagram, i'll bring the multimeter with me the weekend!, and yes, it does not work at all, and when it works, it works at all speeds.

 

[fabianoliver]

Another thing changed too, may be is not related to that, but a month ago, if iddling eith the slider in OFF position, and suddently move it to the defrost, i heard the rpm's increases, not now anymore.
By the way, why the engine revs higher when i slide the slider from off to defrost? thanks for share your knowledge

 

[96AWD5.LOL]

Compressor turns on in defrost. When it does the engine should compensate with slightly higher idle.

 

[J_C]

Another thing changed too, may be is not related to that, but a month ago, if iddling eith the slider in OFF position, and suddently move it to the defrost, i heard the rpm's increases, not now anymore.
By the way, why the engine revs higher when i slide the slider from off to defrost? thanks for share your knowledge

If the engine is still idling smooth, I wouldn't worry about it, but if it drops too low, the first thing I'd check is the IAC valve, might need cleaned out or replaced if it has too much wear. When cleaning them, I like to finish with a drop of light oil on the internal shaft where it meets the bushing and leave it sitting propped upright for a while so gravity helps the oil to flow down into the bushing.

 

[410Fortune]

Blower motor issues likely the resistor as stated above by @Motorhogman

1993 FORD EXPLORER 4.0L V6 Blower Motor Control Module / Resistor | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

 

[olddaddy75]

My F150 did that, it was the brushes in the blower motor, replaced the blower motor, and works fine after 3 1/2 years.

 

[J_C]

Several parts of the system can go bad after this many years, or just be that a mouse ate the wiring.

If it's the resistor, it should still work on highest speed as that bypasses the resistor.

All else fails, take the blower motor out and hook it up to a tool battery... it's a standard brushed DC motor, will survive 18V (if you don't have 12V tools) for a moment of testing. I wouldn't try 24V or higher batteries, not when you could just go to a little more trouble and jumper from the vehicle battery if it comes to that.

 

[fabianoliver]

Thanks again for your answers!
I've some 16V batteries, so i'm able to test the motor straight ahead. I'll do.
txs 410 fortune for the link
I’ll check again if the “system” continues to rise rpm’s when in defrost, it did it a couple month ago.
Previous owner removes AC compressor and related lines fluid lines.
Is the compressor linked to any vacuum line?

 

[J_C]

The compressor has no links to a vac line.

 

[Steve Forbes]

Hello all, my blower motor ( 1994 XLT) stops working for one day a month ago.
Next day, it starts working ok, until today. A rainy day.
I read here that blower motor problems possibly are related to a fuse or relay .
My question is, can a relay works sometimes and other days not? or once bad, it stops working forever?
Can someone has a picture were is located the blower motor relay and how it looks?, and the fuse?
Another ideas ? bad electrical contact maybe?

Thanks all for your comments

Hello all, my blower motor ( 1994 XLT) stops working for one day a month ago.
Next day, it starts working ok, until today. A rainy day.
I read here that blower motor problems possibly are related to a fuse or relay .
My question is, can a relay works sometimes and other days not? or once bad, it stops working forever?
Can someone has a picture were is located the blower motor relay and how it looks?, and the fuse?
Another ideas ? bad electrical contact maybe?

Thanks all for your comments

In my experience, a relay can work intermittently. A fuse just goes out and is done. The most likely trouble maker will be the switch or a ground problem. I would begin by swapping or replacing the relay. If you have access to a spare switch then try that next. After that then check your ground points. It is also that a wire is worn but, that doesn't happen often. However, since you will be messing around with the wiring harness it won't hurt to take a close look at the wires and points of connection.

I hope this helps a little bit. Good luck.

 

[fabianoliver]

In my experience, a relay can work intermittently. A fuse just goes out and is done. The most likely trouble maker will be the switch or a ground problem. I would begin by swapping or replacing the relay. If you have access to a spare switch then try that next. After that then check your ground points. It is also that a wire is worn but, that doesn't happen often. However, since you will be messing around with the wiring harness it won't hurt to take a close look at the wires and points of connection.

I hope this helps a little bit. Good luck.

Thanks Steve, i'll follow the cables all the way i can, luckely the truck has been well trated by the one that loves it, and just neglected by the other owners, no one has messisng arround with mods, bad repairs, and inventions

 

[hjc4604]

Hello all, my blower motor ( 1994 XLT) stops working for one day a month ago.
Next day, it starts working ok, until today. A rainy day.
I read here that blower motor problems possibly are related to a fuse or relay .
My question is, can a relay works sometimes and other days not? or once bad, it stops working forever?
Can someone has a picture were is located the blower motor relay and how it looks?, and the fuse?
Another ideas ? bad electrical contact maybe?

Thanks all for your comments

Yes relays can stick, especially after 30 years. The contacts are coated to deter pitting but eventually it can wear through causing the contacts to stick. Try tapping it with a screwdriver handle when it's not doing what it should. If the tapping makes it start working, you've probably found your problem.

 

[Steve Forbes]

Thanks Steve, i'll follow the cables all the way i can, luckely the truck has been well trated by the one that loves it, and just neglected by the other owners, no one has messisng arround with mods, bad repairs, and inventions

One other thing that you should investigate is the brushes in the motor. They wear out just like other parts. For now, the most easy and likely course would be to just replace the motor. That will tell you immediately if that was the culprit and safe you a lot of crawling around in awkward positions trying to get meter readings and such.

I'm glad that I can be of some help.