Aftermarket Stereo - No power when freezing - WTF?

[Xpedition99]

Hello all!

Recently acquired a very nice 1999 XLT so thought I'd join the forum. Of course, I come with problems :/

The previous owner told me the radio (stock) doesn't work when it's freezing but comes on after the vehicle (and presumably the inner dash area) warms up.

So I figured it must be the crappy 20 year old stock radio which I intended to replace, anyway.

Replacing the stock radio was on the short list and after doing so I soon found out that the new unit, too, does not power on when freezing outside.

I've pulled the head unit when freezing and tested the circuits: constant power is there, no issues. However, the switchable power is NOT there! I've tried replacing all the relevant fuses, cleaned and bent the fuse blades to ensure a connection and no matter what, no power to the switchable power circuit until something warms up.

I've installed countless car stereos over the years and used to install trailer harnesses and brake boxes for a living so I know my way around car electrical circuits a good bit, and I've NEVER come across an electrical issue like this.

I thought maybe there was a relay somewhere in the circuit but that doesn't seem to be the case.

I'm at a real loss here, please help!

Thanks!

 

[Plati]

Yes. Very odd. Only thing I can think of is that fuse box thing down at the passenger's feet. Its been known to get wet from water infiltration. Water expands when it freezes so maybe there's a connection in there that gets physically interrupted by the freezing (expansion) of water? Longshot but all I could think of.

 

[Xpedition99]

I was wandering about that junction... came across that when reading up on the "brown wire mod" and noticed the stereo wiring inside the dash seems to be coming in from the passenger side. Any diagrams for that junction box so I know where to start poking? It's already warmed up enough to start working today but looking at more sub-freezing temps for the next week or so, so that'll give me a chance to troubleshoot.
Thanks!

 

[Plati]

I would think if you just popped the access panel off and took a look see in there you might get an easy read on any water infiltration. If its bone dry and no apparent corrosion of anything all looking squeaky clean brandy new ... then ???

and if its an aftermarket radio bootleg wired into that panel that should be obvious unless someone did a great professional job which is unlikely ... and you can start by verifying the integrity of that patch cord?

I dont have a wiring diagram for a 99

 

[Xpedition99]

I wired in the new head unit using the factory harness and an adapter.

I pulled the kick panel and all looks fine; no apparent water damage indications nor any wire tapping. Was looking for a wire bundle that has obvious speaker wires to clue me in as to where to start line testing but didn't have any luck with that. I may just look for a switched 12v line under the kick panel and tap into that but I'd like to pinpoint this problem, it's a weird one!

 

[1970Maverick]

Have you tried using a heat gun or hair dryer to warm small individual areas inside the Expy or under the hood when you have the problem? It is a weird problem but I was thinking maybe the freezing cold makes one of the connections points contract or shrink in a way that it's breaking the circuit.

If I understand correctly, all the other accessories that receive switched power work and it's only the radio that doesn't.
I don't know the wiring diagram for your year but, if you can find a point in the fuse box that is being switched could you run a new power lead from that point to the radio?

I live in FL now so I don't have the freezing temps but I lived in CT, NJ and KS and I remember doing work on my vehicles in blowing snow and (-)10 degree weather so I can appreciate your situation.

I'm curious to know what you find.

 

[Trainmaster]

My 2000 did the same thing, but the problem was in the heas unit's volume control rheostat.

You need a schematic and a test light. If I remember correctly, there's no electronics in the circuitry that activates the power. That leave you to look for a bad connection.

 

[1970Maverick]

I stumbled across this https://www.fordforumsonline.com/threads/ford-expedition-radio-wire-diagram.3884/
If this is what you need, it looks like the switched power comes directly from fuse, through 2 connectors and into the radio. Hope it can help.

 

[Xpedition99]

Thanks for all the replies and ideas!

The heat gun/hair dryer is a great idea but I don't have either so I'll just have to try the hard way.

I do have a test light and a loose connection in a connector along the way seems like the only real option at this point.

All other electronics work as they should; this is the only electric gremlin in the vehicle.

That chart is super helpful! Now I know what color wire to look for, and the other colors in the bundle. That will make it much easier to trace.

I'll keep the thread updated and welcome any further input in the meantime.