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1974 Opel Manta Luxus
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Discussion Starter · #1 ·
Previous owner said there is a battery draw, and I noticed the radio stays on with the ignition off:
436225

it’s not an original radio but seems to be a vintage AM unit. It should still be wired to the ignition switch and not directly to the battery, right? I haven’t traced the wires yet.
Thanks.
 

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Just Some Dude in Jersey
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Modern stereos are connected to both the switched(ignition) and unswitched(battery) circuits of the car. This separates the power to maintain memory of station presets, the clock, and other low power electronic functions from the stereo's high power functions. Doing this also prevents all the power to the stereo from running through the ignition switch. Main power for amplification and other high current draw functions comes from the "Battery" power connection, the "Ignition" power should ideally only power the low current logic circuits that turn the stereo on, power the clock, and the internal relay that turns on the "Battery" power connection. Your car probably has both the "Ignition" and the "Battery" power connected to the live, on all the time, straight power from the battery. This is commonly done by many people because our cars don't have an Accessory(ACC) position on our key switches that would allow us to listen to the stereo without powering up the whole car and/or starting the engine. If your car is wired like this, you should connect the stereo's Ignition power to the car's ignition power circuit somewhere. It appears that your car has the stereo powered up and fully turned on all the time, which will cause a fair amount of parasitic draw.

On the subject of parasitic draw, I have had a problem with that on all the GT's I've had for over 40 years. For me, this has been a huge problem over the decades. For much of that time I didn't have a convenient way to put the car on a battery charger. Even with no fancy stuff in the car, like I have now, and just a radio, I would seem to have a weak battery after just 3 days of not driving the car. It's been said to me that this was caused "hysteresis" loss, where power just evaporates into the air via all the old corroding electrical connectors in the car. The only way I was able to stop it was to install a battery disconnect switch.
 

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Radios were installed at the dealer. That radio is the original and there is no reason to not switch the power except if you like to listen to it when parked. I never even turned it on and the antenna switch wire was broken so I didn't try that either. It was way down the list. I was told the original owner used to like to drive the Manta to get ice cream. He was also a big guy so that is why the driver seat frame may need to be straightened. I thought that seat had too much wear for a 17K car but that was the explanation. So that may be why it was hard wired.

Put a meter (measuring dc current) or test light between the positive cable and the positive terminal of the battery. Unplug things or remove fuses until the light goes out meter changes. Make sure door switch is closed. I still think the clock could be the culprit. If the radio is turned off, it should have no draw. The clock isn't working but if it is trying to wind the spring which should only be intermittently then it could be a constant draw. Installing the tach would then be the easy fix.

Gordon, the electricity doesn't evaporate. Conservation of energy and all. The power finds high resistance paths to ground and the electricity is converted to heat.
 

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Solo II is fun in a GT!
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Gordon, the electricity doesn't evaporate. Conservation of energy and all. The power finds high resistance paths to ground and the electricity is converted to heat.
now that's hot.
 

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Opel Key Master
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5,288 Posts
Timbo , that is not a factory radio in his picture, the greenish light gives it away. Now on some of these radios, you have to manually turn them off, but you should be able to find a fuse that is ignition on, and pull its power off of it just fine. The Kadetts had you put the power at got all the time, and you manually turned it off. Easy enough to swap over. I tell folks to hook up the A/C kits to power all the time. That way you have to turn them off, and then you don’t have the extra load when starting the car back up
 

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I didn't say it was factory, I believe it's the radio that the Buick dealer had on the shelf. You can turn that radio off with the knob. Maybe the first owner installed it since my 73 had no radio but it is "of the period" and was installed near the time of initial purchase. Even my first radio was FM stereo.
Motor vehicle Automotive design Personal luxury car Car Automotive wheel system
 

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As far as I know it is the original radio. By that I mean there was no radio in the car until this one was added. But since they were shipped without radios, I guess you could argue that is is not.
 

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Opel Key Master
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What makes you so sure they didn't ship the cars with the radios? You could get radio delete in Kadett and Mantas, but you couldn't with a GT, and you know they didn't install GT radios at the dealer
 

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1974 Opel Manta Luxus
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73 Posts
Discussion Starter · #11 ·
I knew the radios were dealer installed, but figured it wasn’t the dealer one because I thought they were this one:
436255

But I forgot that the ignition switch didn’t have an Accessory position. Just wondering if they were supposed to be hot all the time. As soon as I get a test light or multimeter I’ll check to see if there’s a draw there.
 

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That sure is a nice looking classic radio. I remember the old cars we used to be able to sit & listen to the radio while my mom or grandma went in to the store then they changed it some time in the 70’s I think so you had to have the key, there went our fun when we were kids when our parents went in to the store our parents weren’t leaving us the car keys. I just remember you could always hear it so that made you turn it off before you got out of the car. I’ll bet that gem hardly draws an amp.
 
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