1985 parasitic battery drain problem
Thread Starter
2nd Gear
Joined: Aug 2025
Posts: 2
Likes: 1
From: Parker, CO
1985 parasitic battery drain problem
I've searched the forums and haven't found this issue so here goes...
1985 that I bought new and now has just under 50K miles. Parasitic battery drain problem that I have narrowed down to the circuit that drives the dash. As that is WAY beyond my DIY skills to fix, does anyone have a mechanic or shop who is capable of repairing this issue? Preferably in Colorado but I would consider taking it to a neighboring state. The dash lights up and works like it is supposed to do so I'm a bit confused as to why it is that circuit that is draining the battery. About the same time I noticed the battery drain, the radio quit working but I know it's getting power as the antenna goes up when I turn it on. I have also pulled the fuse for the radio but the drain still continues. I have no idea if those two issues are connected. One person on the local Vette users group forum suggested I install a battery cutout switch but I am already pulling that battery cable loose when I garage it so I'm not sure that would give me any benefit.
PS - The drain will take the battery down in less than a week - maybe 5 days before I have to put a charger or jumper cables on it to start it.
HELP!!
1985 that I bought new and now has just under 50K miles. Parasitic battery drain problem that I have narrowed down to the circuit that drives the dash. As that is WAY beyond my DIY skills to fix, does anyone have a mechanic or shop who is capable of repairing this issue? Preferably in Colorado but I would consider taking it to a neighboring state. The dash lights up and works like it is supposed to do so I'm a bit confused as to why it is that circuit that is draining the battery. About the same time I noticed the battery drain, the radio quit working but I know it's getting power as the antenna goes up when I turn it on. I have also pulled the fuse for the radio but the drain still continues. I have no idea if those two issues are connected. One person on the local Vette users group forum suggested I install a battery cutout switch but I am already pulling that battery cable loose when I garage it so I'm not sure that would give me any benefit.
PS - The drain will take the battery down in less than a week - maybe 5 days before I have to put a charger or jumper cables on it to start it.
HELP!!
Melting Slicks
Joined: Nov 2016
Posts: 2,256
Likes: 3,082
From: So Cal
2023 C4 of the Year Finalist - Unmodified
I'm also an Original Owner of a 1985. Welcome aboard.
If the parasitic drain is on the LCD fuse, there is a power switching transistor in the cluster that has failed in the ON state. The dash still functions normally, but the electronics still draw about 250 Milliamps. About 6 A Hr a day, 41 A Hr a week and it won't start. This malfunction is easy to verify. Put your meter across the LCD terminals (fuse removed). Start the engine and observe the reading. IIRC it will be about 250-ish Milliamps. Turn the engine OFF. The LCD current should drop to about 25 Milliamps. If it remains at 250, the transistor has failed.
Batte electronics is the go-to source for info, repair kits and parts, and send-in service. batee.com.
For the radio, CLOCK/CTSY also provides power to the radio. This fuse also powers the antenna, which works, so you don't have a fuse problem. It sounds like the radio has an internal problem which may have been brought on by low voltage, jump starts, etc while dealing with the low battery events from the cluster draw. There are lots of radio repair outfits, I've used some, but I personally like Dr. Dons in Texas the best.
Removing the cluster and the radio is pretty basic. There's some tricks to know, and a 7mm hex socket or nut driver is imperative, it isn't tough. Contact the people in the links, and decide what you want to do. If you need guidance to get them out of the car to send them in, ask. I and others can help. It's not tough.
Cheers.
If the parasitic drain is on the LCD fuse, there is a power switching transistor in the cluster that has failed in the ON state. The dash still functions normally, but the electronics still draw about 250 Milliamps. About 6 A Hr a day, 41 A Hr a week and it won't start. This malfunction is easy to verify. Put your meter across the LCD terminals (fuse removed). Start the engine and observe the reading. IIRC it will be about 250-ish Milliamps. Turn the engine OFF. The LCD current should drop to about 25 Milliamps. If it remains at 250, the transistor has failed.
Batte electronics is the go-to source for info, repair kits and parts, and send-in service. batee.com.
For the radio, CLOCK/CTSY also provides power to the radio. This fuse also powers the antenna, which works, so you don't have a fuse problem. It sounds like the radio has an internal problem which may have been brought on by low voltage, jump starts, etc while dealing with the low battery events from the cluster draw. There are lots of radio repair outfits, I've used some, but I personally like Dr. Dons in Texas the best.
Removing the cluster and the radio is pretty basic. There's some tricks to know, and a 7mm hex socket or nut driver is imperative, it isn't tough. Contact the people in the links, and decide what you want to do. If you need guidance to get them out of the car to send them in, ask. I and others can help. It's not tough.
Cheers.
Last edited by IHBD; Aug 11, 2025 at 09:16 PM.
Thread Starter
2nd Gear
Joined: Aug 2025
Posts: 2
Likes: 1
From: Parker, CO
Wow... I can't believe you've provided such a complete answer almost immediately to my problem. I have been querying every shop and dealer in the Denver area and all have said they don't want to touch it. We did have one quality Corvette shop here some time back - Corvette City if I recall correctly who might have had the expertise you have but he closed his shop some time back.
Thank you, thank you, thank you! You have given me a starting place and I will run the test with my meter that you suggest. If it is as you suspect, I'll start doing research to see if I'm up to the task of tackling this.
Thanks again!
Thank you, thank you, thank you! You have given me a starting place and I will run the test with my meter that you suggest. If it is as you suspect, I'll start doing research to see if I'm up to the task of tackling this.
Thanks again!
Le Mans Master
Joined: Jul 2004
Posts: 6,228
Likes: 698
From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
Wow... I can't believe you've provided such a complete answer almost immediately to my problem. I have been querying every shop and dealer in the Denver area and all have said they don't want to touch it. We did have one quality Corvette shop here some time back - Corvette City if I recall correctly who might have had the expertise you have but he closed his shop some time back.
Thank you, thank you, thank you! You have given me a starting place and I will run the test with my meter that you suggest. If it is as you suspect, I'll start doing research to see if I'm up to the task of tackling this.
Thanks again!
Thank you, thank you, thank you! You have given me a starting place and I will run the test with my meter that you suggest. If it is as you suspect, I'll start doing research to see if I'm up to the task of tackling this.
Thanks again!
