Aloha!

I hate for my first post here to be a request for help, but I'm stumped, and I'm hoping someone here has experience that can help me. Apologies in advance for a long post...

I have a 1992 Accord LX with 147,000 miles on it. It usually runs well. I bought it 6 months ago. I knew the radio [stock, nothing fancy] didn't work all of the time. It cut in and out at odd times, but hey, it's a 19-year-old car and the radio is only cosmetic, right? So I didn't think much about it.

I recently left the car parked for a week, and when I came back to it, the battery was dead. I know I hadn't left lights on or anything -- I'm pretty fanatical about checking those, even the dome light -- and when it started after a jump-start, I scratched my head, but didn't think much of it.

Driving home, I noticed that the radio was totally dead, but when I turned on the headlights (or even the running lights), the radio came back to life.

I thought, "maybe there's an internal short in the radio." I pulled it out, unplugged the power harness and the antenna, and found a spot where the casing is scorched -- it looks like maybe it got wet (the car had a leak in the roof when I bought it) and shorted out. So I didn't put it back in -- problem solved, I thought.

Today, the car started REALLY sluggishly at home, and when I left it parked at the post office for 10 minutes, it died. I was able to jump-start it again, drove it to the garage, and they assured me that the charging system is A-OK and that they can't detect a drain on the battery. Wiring is good, they said; no problems. They charged the battery and all appears well.

The mechanic noted that the electric cooling fan behind the radiator, which runs after the car is shut off, draws a lot of power and might be running for too long, thereby killing the battery.

So: my first 4 questions:

1. Has anyone else here had this problem?
2. What regulates how long the fan runs?
3. Is the fan really necessary? I unplugged it and drove home, watching the temperature gauge the whole time, and it never moved above normal.
4. Is this a thermostat problem? Is there perhaps a "stuck" sensor for the fan?

The garage guys haven't looked inside the cabin, only under the hood.
I suspect it might be the ignition switch -- perhaps it's so worn that when I shut the car off it's not entirely 'off'. Is this possible?

And can anyone help me figure out why the headlight switch turned the radio on? I am guessing that the circuit that told the radio to dim the dial for night driving somehow ran "around" the circuit that supplied power to the display for daytime driving. Is that possible? Or do I have a larger problem?

As I type, the car is in the driveway, cooling fan unplugged, awaiting tomorrow's test of the "fan-kills-battery" hypothesis. Hopefully it will start.

Just in case, though, I've left it an offering (my daughter's lemonade and a piece of chocolate cake).

Perhaps it's all karma for covering the car in wood-grain contact paper (like an old Woody station wagon) and cheap red paint...?

Thanks, all of you, for any ideas you might have.

 

Your headlights turned on the radio I'm guessing because there is a short circuit somewhere in the radio/harness that allows the power from the dash lights to switch on the radio. Especially since there is a scorch mark on the casing it's probably toast.

When the car is off the radiator fans are controlled by two thermo-switches. There is one on the thermostat housing and one on the water outlet on the front of the head (upper hose). One comes on between 194* and 205* (F) and the other 217* and 228* (F) IIRC. Each one controls one of the fans. They also allow the cooling fans to come one during the period of heat soak where coolant temperature increases immediately after shutdown. Once the temperature goes back down the fans come off.

A short across those two wires will cause the fans to come on.

Behind your glovebox there is a radiator fan control module. It should be clipped to the frame and the plug looks like a phone jack. If this has somehow failed or shorted it could be keeping the fans on.

Yes, the fan is neccesary. Otherwise the engine can overheat after shutdown due to heat soak.

 

Hi chikin pickle --

Thanks for the 411. I didn't know about the second t-stat switch on the fan -- I saw the one on the thermostat housing, but didn't see the one on the front of the head. I'll look. If either switch is misreading the temperature, that could mean the fan is staying on too long.

I'm thinking now that the short in the radio helped kill the battery; jumpstarting and driving for an hour didn't fully recharge it, and then the fan being on too long drew the battery back down to "no charge" again.

Is that control module behind the glovebox a chip? What process is it regulating?

I don't think the block is overheating after shut-off -- I'd see that on the temperature gauge, right? I've turned the key to the "instruments-on" position and the temperature continues to fall once I've shut off the car.

Forgive an ignorant question, but what are the consequences if the car overheats while it's not running, during the heat soak period? I assume the coolant would expand, and perhaps overflow into the reservoir. Would it also stress the gaskets (head, oilpan)?

Thanks -- I appreciate your help.

 

A few things....BOTH fans should run while the car is on and the temp goes up, BOTH should also run when the ac is on....please verify this?

When the car is off, the switch on the upper hose (the 217 to 224) controls one fan to run.

So please confirm the first question. Then, next time you can, after a nice long drive and you return home.....turn the car off, let it sit. The fan should kick on (again it has to be hot), once the fan comes on, start a timer.....the fan should run for up to ~10 minutes and then go off.

Last thing....how old is the battery and how did it test out?

 

Hi poorman --

OK: Both fans do run while A/C is on, but I'm unable to confirm that they run if the car is hot. Only one fan -- the passenger-side one -- runs after the car is shut off. That fan seems to run, as you said, for ~8 minutes before shutting off.

The battery is pretty new -- Dec. 2010. A charging-system check at the local garage indicates that the charging system is working as designed and that the battery is OK.

The problem seems gone, for the moment -- I really am starting to think that I unplugged the radio, (meaning that there's no drain on the battery when the key is removed from the ignition) but that the charging system must have had insufficient time to fully charge the battery after jumpstarting it. I only ran ~30 minutes on the way home from the airport. Subsequent attempts to start the car pulled a lot of power out of the battery and left me flat again. Since I had the battery charged at the service station, I've had no problems with the battery.

Am I dreaming? Do I have a larger problem lurking? Should I trade the car in before it dies? ;-)

Thanks --
Greg

 

I honestly don't know about overheating when the car is off. But the main thing I would be concerned about is the head gasket. Aluminum engines dislike overheating with a vengeance. Even the blocks can warp.

If you want to test the switch, get some boiling water and a thermometer. Put the switch in the water and heat it up, then test it for continuity. As it cools off it should open and the continuity will disappear.

I think you are more than likely being paranoid. 30 minutes wouldn't charge the battery very much I wouldn't think. Just keep an eye on it. If it hasn't come back I would say that the radio was more than likely the culprit.

 

One fan running when the car is "off" is normal.

Something drained, or might have, the battery while sitting for a week. Going to be hard to figure out when everything is working...heck I've seen glove box lights stay on and kill a battery after a long period of sitting......

 

I have the same problem with the radio turning on and off with the headlights on my '91 Accord LX. Was it definitely a short in the wiring harness? Did you replace the radio and the problem went away?

BTW, the control unit underneath the dash below the glove box is the Automatic Transmission Controller (ATC). I had to replace mine a year or two back. Easy to replace and I found a recondition for swap resource online online for $140. Great deal.

Thanks!!!