My overdrive indicator light located on the end of the wiper switch is blinking

Error in the torque converter/transmission. Need the code read to see if there are additional check-engine issues. There usually are.

you sure you got all the wires in the correct location on new alt?

this could be a couple of problems the switch itsself would be the first thing I would check fords are bad on them going out. Does the overdrive light ever blink on and off?

Blinking O/D light is a warning to the driver that they should take it to a qualified repair shop. Also for the technician that DTC'S - diagnostic trouble codes are stored that will point a qualified tech to a problem for testing , electrical circuit's ,componets etc.... You have no idea of the complexity of these systems . Your best bet ,take it to a qualified repair shop !
Transmission Control Indicator Lamp (TCIL)
The transmission control indicator lamp (TCIL) is located in the instrument panel and is labeled O/D OFF. It is illuminated in conjunction with the TC switch.
The TCIL will flash if the EPC solenoid circuit is shorted or a fault has been detected in a monitored sensor used for transmission operation.

This is indicating an issue with the transmission that should not be ignored. The flashing light was designed to annoy you into action. Waiting could cost you a lot more money. I would get the error codes by asking my local shop to get them, or many chain auto stores offer free code reading, just ask. I was at AutoZone a few weeks ago and got the codes, and they printed them off for me, in addition to recommendations as to the cause.
Best case scenario is just a reset is necessary (computer perhaps). You don't want to be stuck on the side of the road, so it's good to find out.

Good luck and let us know how it turns out.

either pull fuse until u replace the switch

The procedure for re-setting the HVAC control panel on a 1998 Dodge Grand Caravan follows:
With ignition on but not running
1. turn knob to air vents
2. turn fan knob to ON
3. temperature setting on COLD (2X) {I have dual temp controls}
4. hold top(rear wiper) and bottom (rear wiper with wash) buttons pressing down together until all the buttons cycle through (this will require 1 to 2 minutes of continuous pressing)
I learned this from a very helpful local Dodge service adviser

This blinking light indicates a problem. You will have to have it scanned for trouble codes to find out
what it is.

I respectfully disagree with C17Hydro.

The OD light is "on", because somehow, someone has accidentally turned the OverDrive switch to the "Off" position. This switch is located on the transmission shift lever. When the button is "in", the overdrive is engaged; this is where the switch is supposed to be, to give you maximum fuel mileage. When the button is "in", the light is turned off. When the button is "out", the OD is dis-engaged, and the light on the dash illuminates to indicate to you that the OD is "off". Unless the OD light is blinking rapidly, you have NO transmission issues.

this could mean there is a problem with the transmission,but most times when OD light is flashing it is because the wiring to the OD switch is broken.
is the OD switch on the end of the gear shift lever ?
or does your vehicle have the shifter on console between seats ?