2003 Ford Windstar erratic instument cluster & ac fans

[SamnCare]

I have a 2003 Ford Windstar with instrument cluster acting erratic and rear and front ac blower motors speed up when I accelerate rpms above 4k, I kind think it may be the alternator. I pulled the interment cluster apart and reflowed the two ribbon connector solder points, but still have the same problem. Also I disconnected the plug that goes to the alternator and revved the engine up to 4k rpms and it still did the same erratic needle swing and ac blower speed change. Then I unplugged the alternator connector and the Red wire that goes to the batt from the alternator, revved it up again and no problems with instrument cluster or ac fans? Would you say it the REM or the alternator?

[scubacat]

Almost certainly the alternator. You just listed every single usual symptom.

BUT test the battery first. Drop by advance auto and they'll test them both plus the starter for free with the machine right in the parking lot.

[12Ounce]

I would also check the power relays for aging contacts.

[scubacat]

That's a lot of relays to have continuity errors like that at once, and especially with the revving causing the fan to blow faster, that's almost definitely battery or alternator. The free check at advance or autozone or oreilly will clear it up pretty fast either way

My money is on alternator (or both battery and alternator)

[wiswind]

The fact that you can hear your fan speeds vary like you mention is an indication that the voltage level in the whole vehicle is changing.....this should NOT happen.

The voltage regulator is part of the alternator.
If you have a defective battery....it can be placing a extra load onto the alternator.....
If your battery is 5 or more years old....I would change it.
I mention this because a bad battery can cause your NEW alternator to burn out.
It is NOT unusual for a vehicle to need both a battery and alternator within a short period of time.....

Also verify that you have good connections at the high power connection locations....on the battery, alternator AND on the Starter.
Corrosion on the starter connections can cause issues.