Accessory Electric Circuit - 740

petershen1984 · Post by **petershen1984** » 26 Mar 2004, 11:26

Could anyone tell me where to look if sometimes your accessories don't turn off with the ignition switch? Several times now the seatbelt clicker continued to flash when I switch off the car--which I remedied by leaving the buckle locked. Today, I forgot to turn off the rear-defrost when I left the car--but it continued to run even in the key-off position--and it drained my battery of charge within 7 hours..

And yes, my headbeams were somewhat affected by this too--they wouldn't switch on once.. had to reboot car

Perfect lesson learned to turn off all switches where possible to avoid this disaster. For instance, a few years back the A/C radiatior drained the battery--it was the first thing to start when the jumper battery is connected. Fortunately, my rescue kit includes a jumper cable, saving me a call to the repair shop

at 11:00 pm.......

LaRy · Post by **LaRy** » 26 Mar 2004, 12:33

If the common grounding for the relays in the car is bad you get crazy problems. Some relays will be fed "backwards", and that will make them stay on. In your case I would look at the big grounding terminal list, especially the one placed behind the panel at the right side foot well, the panel with the fresh air vent in the middle. The grounding for most of the relays are placed there. I have had problems caused by bad grounding, making relays stay on even when the ignition switch was in off position, at the same time some functions was not working when the car was running. Check that all ground connections at this terminal list are tight and clean them if they have oxidation. Some of these flat AMP connections are getting "tired" after all these years. Check also that the terminal list itself has a good connection to ground without oxidation.
If I don't remember wrong, you will also find a similar ground terminal at left side foot well, check also that on.

Volvord · Post by **Volvord** » 26 Mar 2004, 16:20

It could likely be the ignition switch, these are a common replacement item and easy to replace. The "key part is not replaced, just the electrical swich part on the back of the ignition switch. It is held in place by two screws from the back, akward to get at but ...

petershen1984 · Post by **petershen1984** » 26 Mar 2004, 20:17

LaRy wrote:If the common grounding for the relays in the car is bad you get crazy problems. Some relays will be fed "backwards", and that will make them stay on. In your case I would look at the big grounding terminal list, especially the one placed behind the panel at the right side foot well, the panel with the fresh air vent in the middle. The grounding for most of the relays are placed there. I have had problems caused by bad grounding, making relays stay on even when the ignition switch was in off position, at the same time some functions was not working when the car was running. Check that all ground connections at this terminal list are tight and clean them if they have oxidation. Some of these flat AMP connections are getting "tired" after all these years. Check also that the terminal list itself has a good connection to ground without oxidation.
If I don't remember wrong, you will also find a similar ground terminal at left side foot well, check also that on.

I had my A/C system overhauled last November--where they retrofitted R134a and replaced a leaking radiator and the drain cover, possibly loosening a few relay connections.

Above the passenger footwell will be the first place I check. Thanks!

petershen1984 · Post by **petershen1984** » 26 Mar 2004, 23:46

Volvord 784VC wrote:It could likely be the ignition switch, these are a common replacement item and easy to replace. The "key part is not replaced, just the electrical swich part on the back of the ignition switch. It is held in place by two screws from the back, akward to get at but ...

the switch itself isn't bad.. it doesn't behave as if it's stuck in the ACC position--cuz the radio turns off, the high beams are inhibited, but the rear-demist and seatbelt warnings continue flashing. it happens randomly, not every time. Thanks though

LaRy · Post by **LaRy** » 27 Mar 2004, 01:58

When different odd electrical faults are happening in a car it is most likely a bad ground connection. Maybe i should explain what I mean by "backfeeding". In a car, electrical functions are switched on or off sometimes by opening the 12 volt circuit, but also very often by opening the connection to ground. If you loose the normal ground connection, the electric circuit will always try to find the "second best" way to ground, and if this second best way to ground is through some relay coil, the relay will stay on, it will sometime get in to an electrical self holding circuit, so it doesen't matter if you turn the key switch off, like your A/C fan. This is sucking out the battery. The second best ground could be through the relay coil and then in serial through the rear defrost or the AC fan motor winding. Your solution for the moment is to switch of all functions of the car, to avoid this backfeeding. You will also find two important ground terminals under the hood, at the sides just behind the headlights. These ground terminal lists have very often oxidation.

To make it clear, the ground terminal in the foot well is placed behind the side panel in front of the door, 10 cm above the floor.

petershen1984 · Post by **petershen1984** » 27 Mar 2004, 05:11

Thanks for all the great insight, Larry, I'll have it looked at and follow up soon.