Wire to battery caused onboard computer problem

[W8ENG]

I have an Icom IC-207 (50 watts on 2m) wired directly to the battery in my 2000 Chevrolet Impala. Recently the check engine lite came on, when I took the car to the dealer they said their was a "low voltage fault" in the cars computer.  According to the Service Manager when power to the on-board compter drops below 12 volts a fault occurs and weird things start happening (my temp gaguge did not work, engine cooling ran ran constantly and AC would not work) They suggested commecting the radio to the fuse block.

Are thier any problems with connecting to the fuse block, other than needing the key on to use the radio?

I don't want to eep having problems with the computer (at $70 a pop to fix!)

Chevy sells Impalas as police cars, so I assume the electrical system must be fairly substantial.  I've thought of adding a second battery in the trunk, but that would be a lot of work.  Any help would be appreciated.    

[K5TEE]

What ran the battery down? were you using the radio for a long peroid of time without the car running?
Running the radio with the car running will NOT run down the battery unless the alternator is bad.
GM recommends running the radio leads to the battery with fuses at the battery. Go to this web site for more information from GM:
http://service.gm.com:8083/techlineinfo/radio.html
Car starting batteries do not like to be drained down  and then recharged. If you are using your system in that fashion, I would suggest you put in a second battery in your car that is a deep cycle battery and use it just for the radio. This way, you can use the radio with the car off and not worry about draining down the main battery.
If the radio was not being used except only when the car was running, then you have other problems with your electrical. A 50 watt radio at 12 volts will pull about 12 amps Max. and your alternator is rated at about 95 amp output. So you see, your alternator should not have any problems keeping the battery charged.
I hope this helps in your quest.
Tom
K5TEE

[W8ENG]

Tom,

Thanks for the info.  The problem was intermittent at first, then the problem light came on perminantly.  I was not running the radio without the car running.  I agree that I probably have a problem with the alternator or battery.  I'm going hook a volt meter and up in the car for the next few weeks and see if that shows anything.

Mike, W8ENG

[N3XPF]

I don't get the "CHECK ENGINE" light thing.  When mine came on, I checked--and the engine was still there!


Anyway... Don't know if it applies to GMs, but you can get a $35 handheld plug-in scanner for Fords that'll make the computer run thru its diagnostics and give you result codes.  That'll save you the hassle of running to a dealership.

About the voltage, have you ever noticed the battery light (or "amp" or "charge" or whatever the Impala has) come on?  For a few seconds after startup is a good thing, but to stay on or come on later is a Bad Thing.  If you do find an electrical fault, you'll probably have to yank the radio (and wiring) completely to convince a dealer it's a Chevy problem and not your problem.  This is doubly so if it's under warranty  There is no reason that alternator can't handle a measly 12 amps.  

[KQ4BX]

When you key a 50 Watt radio, you can draw up to 12 Amps or more. If your battery is old, it can have some weak cells. Each weak cell will cause the voltage to drop. Putting the radio on the battery will have the same effect, even if it goes to a fuse first.  The prefered method is direct to the battery, through dedicated fuses on both legs of the power cable from your radio.
A bad battery, depending on how bad it is, will not show it's bad right away. Now you come along an draw 12 Amps out of it, plus what the car draws. You could have a bad cell, bad alternator, but you do not need to route the power wires to the cars fuse block.

[W0JOG]

Mike, and anyone else doing an installation of amateur radio gear in a newer automobile, there are a lot of ways you can cost yourself a lot of money by frying on-board things with chips in them.

GM, for one, is quite helpful if you will ask. They have installation guidelines available via http://service.gm.com/techlineinfo/radio.html and the toll-free number for customer service. If you go the phone call route, you will have to persist to get past the person who answers and who doesn't have a clue about what you are talking about. But they DO support installing after market RF devices. And to try it without their input is expensive folly.

[AA4PB]

It seems to me that *if* the current drawn by the radio is causing the battery voltage to drop, moving it to the fuse block will not correct the problem. It will still draw the same current from the battery. Personally I wouldn't put too much faith in what a dealer tells me about an electrical problem.

Perhaps the problem with the computer was caused when you disconnected the battery to make the radio connections. If you made an intermittant connection (on off on off on) when putting the terminal back on the battery post, that might have set a low voltage code in the computer.