2000 Ford Eddie Bauer Explorer blower motor will not start when outside temperature drops into the 30s or 20s overnight. Drove about 15 miles today no blower. Vehicle sat for 2 hours , started it to leave and blower started working.
As with many other circuits, the best way to tackle this after checking easy things like removing the fuse, examining the contacts, swapping the relay with another of same type, is to use the schematic and a multimeter to trace where power stops.
This link is the entire 1999 workshop manual climate control section which includes some troubleshooting steps:
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the forum software is doing something screwy in my browser and always shows the link trying to "loading" but ignore that, it's just a link to a PDF that can still be clicked to get the PDF file).
Also attached below is a '99 EATC and manual control versions
wiring diagram PDF files if you have basic electrical troubleshooting skills already and just need that. Since you have an Eddie Bauer, you probably have the automatic EATC climate control with the digital head unit?
If the "various tests" don't find a problem in warmer weather, then you will need to test in colder weather.
The easiest way to verify it's the motor is to see if power is getting to it. One contact on the motor connector will be ~12V, and put the other multimeter probe on a chassis ground point (anywhere), NOT on the other blower motor connector contact. You don't need to figure out which wire is which, just put one meter probe on chassis ground and try both blower motor connector contacts - of course with the vehicle on and the climate control set to have the fan running, and if either contact has 12V relative to chassis ground, there is power getting to the fan - BUT it is the transistor module (aka blower motor resistor on the manual climate control version) that grounds the circuit. See attached wiring diagram.
If there is no power getting to the fan then you need to look up-steam on the schematic at the blower motor relay. If there is power getting to the blower motor, then whichever blower motor connector contact has 12V, the other blower motor connector contact can be shorted to chassis ground and the blower motor should run, OR you could just pull the blower motor and feed 12V (even 18V for a brief period) from a power tool battery or whatever. If you need to put the blower motor in a freezer to get it cold, you might try that... though taking it off the vehicle, and being at a different orientation, might have different results even at a lower temperature than the exact orientation it has installed in the vehicle.
If the blower motor checks out good, and there's no connector problems, then it's probably the speed controller and with the temperature being a factor, probably a bad solder joint on it... "probably", but after ~24 years a lot could go wrong like the dash head unit itself. The more you have to troubleshoot till you find the problem, the more useful that workshop manual section I linked to, will be.
Another quicker thing to try with the motor still installed and plugged in, is tap the blower motor casing with a hammer or wrench or whatever when it should be running. If the bearings or brushes are intermittently failing, that might be enough to get it spinning and if that works, would be a sign the blower motor is bad (
unless of course, the connector is bad and tapping it, disturbs the connector just enough to make better contact, but you could wiggle the connector itself to rule that out).
If you read this post within the first few minutes of it being posted, then it's probably already been edited again.
