Radio and other accessories power off when cranking

[dbrannon79]

Ok, Here's my story! I installed a Kenwood head unit a while back into my 95 Chevy pickup and recently I have noticed that it must be sensitive to loosing power while cranking the engine. the internal clock has been getting delayed and on occasion the screen will display funky after starting the truck, I'm guessing by the quick losses of power since it has a "boot-up sequence" similar to a mini computer. To me this is kind of an annoyance but I figure there has to be some mod out there that can be done to keep it powered when the key is in the crank position. At the moment all is working as it should, turning the key back will power the radio and the power windows, which I discovered recently and thought that was weird for an older truck but I accepted it and went on. my goal is to find some way to keep the ability to turn the key back for the radio but also keep it powered while cranking. maybe with a relay or something. I have looked over the wireing schematics for the truck but I can't seem to find anything in the schematics that would indicate a power loss to the accessories when the key is in the crank position. any help on where to start would be much appreciated

 

[NVW]

Maybe take power from a BAT. terminal instead of an IGN. terminal?

 

[ak diesel driver]

It might be voltage sensitive and while starting the voltage drops low enough to cause it to reboot

 

[dbrannon79]

I hadn't though of it being voltage sensitive. Ill have to pull the starter solenoid wire and check it I'm actually loosing power while the switch is in the crank position. if this is the case, maybe a one-way diode and a charge capacitor inline with the radio power might do the trick. the other trick would be to build a charge capacitor circuit that could maintain the radio for up to 30 seconds. I've built things like that before but would have to add a regulator for spikes and a relay to disable it when the key is turned off.

 

[Will L.]

It should maintain. I wouldn’t build a work around- find and solve the issue. Or else that underlying problem may pop up and do damage later.

you should have 2 power wires to the radio, one that is constant hot and the other hot with ignition on. Verify that to begin with. If that constant hot drops out while cranking- chase that circuit or the batteries: starting circuit like mentioned above.

 

[smokymtn65]

Does it have a separate battery wire and ignition wire ?

 

[dbrannon79]

It's all connected through the factory harness with an adapter. I did verify which was constant and switched power when it was installed, but never diagnosed the circuit while cranking. I'll have to pull the crank wire to disable the starter and probe both the constant and the switched power to see if ether drop out while cranking this weekend and see what's happening. come to think about it, I forgot that when I first bought the truck I swapped the steering column out from a donor truck because shifter was broken, so I do have a spare ignition switch and harness if I find that it's bad!

 

[Will L.]

Test it with starter hooked up. That amperage draw could e what’s killing power. Can be a precursor to starter, battery cables, etc going bad.
Come to think of it- go check battery connections, especially if you still have the garbage side post connections.

 

[WarWagon]

Radio and other accessories power off when cranking

Normal! This is by design. All power to the starter during cranking and drop every single load that isn't needed to get the engine going. Limits of battery, wires, and crazy voltage swings during cranking is a good reason to keep things "OFF" during cranking. Some aftermarket cig lighter powered devices warn of being damaged if left plugged in during cranking.

If the above sound advice above checks out ... you checked grounds? And I will say it X2: load test each battery separately. It matters not how new they are if you got a dead one. Well, only for battery warranty it matters.

After that IMO the old 'cheap' aftermarket radio has failed. It's like $150 for a new better top of the line 'cheap' one with all the CD player USB phone connect stuff. Cheap is relitive only vs. the OEM standard radio. I don't get out of the parts store for that little...