No Start After Rain, Alarm Flashes

BlackwoodGT · Sep 4, 2017

Just bought a 99 GT convertible 5 speed. The seller told me about this problem, that after a heavy rain, it won't start and the alarm light (factory) flashes. He said to disconnect the battery and reconnect it and its fine. I want to resolve this and figure I'm not the only one this has ever happened to. Thanks!

Jaime Tucjer · Sep 4, 2017

BlackwoodGT said:
Just bought a 99 GT convertible 5 speed. The seller told me about this problem, that after a heavy rain, it won't start and the alarm light (factory) flashes. He said to disconnect the battery and reconnect it and its fine. I want to resolve this and figure I'm not the only one this has ever happened to. Thanks![/QUO
I have a 99 GT it was running and died and want start security light flashes and odometer reads ---------. Is yours the same. I'm trying to figure it out disconnecting the battery doesn't help

wmburns · Sep 5, 2017

Turn the key on but do NOT crank. The theft light should come on and then go out after a 3 second "prove out". Once proved out that means the key has been read and accepted. After successful "prove out" any no start issues are NOT related to PATS.

If there are any theft light flash codes during the "prove out" these should be noted.

Note, don't ignore it if the cluster is displaying all dashes. This could be a symptom of a base power problem such as the PCM not getting power.

Regarding the rain issue. There are a number of possibilities that should be ruled out with a visual inspection.

The PCM in the right hand passenger's seat kick area.
The CCRM in the front right hand fender well.
the GEM behind the dash. The GEM will sometimes get wet from a leak around the cowl area or from the wind shield.
I would also check for water in the doors. The water could affect the door ajar switch and give a false reading.

Water and car's electrical do not play well with each other.

Here's some more information regarding crank with no start check list. IMO the best results can be achieved by following the check list and trouble shooting based upon what the actual symptoms are.

1996+ Crank with no start check list
http://www.allfordmustangs.com/forums/4-6l-tech/336452-1997-mustang-wont-ignite.html#2984838

Brady's 2003GT · Sep 7, 2017

This is a problem I recently had. To unplug the negative battery cable is a temporary fix, but in my case the problem got worse over time. After I purchased a flash tuner (SCTX4) and loaded a tune to my vehicle I haven't had the problem. I guess completely reprogramming the vehicle was helpful because it hasn't happened for about a year.

No Start After Rain, Alarm Flashes

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No Start After Rain, Alarm Flashes

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