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Discussion Starter #1
So I just got done putting in the classic update aaw kit. The new wiring fixed every problem but one that I was having. The last issue I have is when I turn on my headlights with dse headlight door kit my tach shuts off everytime the relay opens and closes. When I have them wired up but with the ground not attached I see 3 volts on the ground wire coming from the control box. The suggestion from DSE was to run the constant power and ground to the battery but that seems like a band-aid approach to finding out what is wrong. So should I see power on the ground wire if the wire is not attached to a ground? Part of my issues before were power backfeeding and now I wonder if the DSE kit was part of my problem before. Any help or pointers of what I might be able to do or check would greatly be appreciated.
 

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It can be normal to read some kind of voltage on a circuit's disconnected ground wire. You're essentially measuring the open circuit voltage and that voltage could be just about anything between ground and battery voltage, so it's not really helpful to know unless you have a known good unit to compare against.

The tach has a lead from the distributor and a power and ground. I would independently measure the voltage of each lead directly from the tach while operating the headlight doors to determine which lead is at fault. My guess is it will be the ground lead. It might be a poorly grounded tach, the return current from the headlight doors might be finding a path to the tach through this poor ground connection which can disrupt normal operation.

It might also be helpful to know the year of your car.
 

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Discussion Starter #3
It is a 1969 and the grounds are all good. The tach uses the same ground as the entire cluster with the aaw kit. When I run the power to the battery and ground left by the emergency brake for the dse headlight module the tach is fine. I use any of the power wires from the aaw kit as the constant for the dse and that is when I see the tach bounce. Also it does not do it when using park lights only headlights. They agreed to send me another module and I should be able to try it again soon. Oh and I also ran a direct ground wire from the battery to the parking brake area where my grounds are and that made no change. This issue like I was saying before happened before my new harness and after. Hopefully it is just a module issue. Thanks for the input
 

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I'm still more inclined to think that the tach is at fault and not the DSE controller. I think you ruled out a bad ground connection to the car body but there still could be a bad ground connection at the tach. It could also be a poor power connection to the tach, you really can't tell until you measure the voltage. It makes sense that the problem only occurs when operating the headlights since that would be the only time the headlight doors operate as the parking lights shouldn't engage the doors. It also makes sense that running a ground wire from the battery to the ground connection makes no change since the car body is actually a better conductor than that wire. Actually what you did was confirm that your ground connection for the DSE controller is good. Another possibility is that where you are taping into the AAW harness is not a good place to use as the wire gauge may not be big enough for the distance that the wire needs to run. You somewhat proved that by running the power wire directly to the battery. Is there a free power tap on the fuse block that you could use? Or why not just run right off the battery since you already know that works.
 

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Discussion Starter #5
Thanks again for your insight. The aaw classic comes with 6-12 gauge wires setup for power seats, windows, etc. I have door poppers, power locks, power windows, line lock, exhaust cutouts, 3 amps for my stereo, power seats and nothing else besides the dse headlights cause the tach to act like this. DSE says that the doors get there power from the headlight switch and that the constant power hookup is just for the relay and draws less then 1 amp. If the new one from dse does not fix it then I will run a new power wire.
 

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Discussion Starter #6
Also to be clear on the tach shutting off when the relay opens and closes. It shuts it off for like 2 seconds each time I turn the lights on and off but the rest of the time it works perfect. I really think the unit is bad and is backfeeding power over its ground causing the tach to not like it. Sorry I was not very clear earlier.
 

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Also to be clear on the tach shutting off when the relay opens and closes. It shuts it off for like 2 seconds each time I turn the lights on and off but the rest of the time it works perfect. I really think the unit is bad and is backfeeding power over its ground causing the tach to not like it. Sorry I was not very clear earlier.
Sounds like the DSE unit might be producing an inductive spike when it opens or closes the headlight doors. May not have clamp diodes on the relay coils and/or actuators. Either that or maybe it is not grounded well as Lee suggested. Bad grounds can make all kinds of crazy things happen...

Don
 

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Is your headlight switch and gauges properly grounded?

Don
 

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Discussion Starter #9
Is your headlight switch and gauges properly grounded?

Don
I would assume so. The switch is grounded through dash ground plate and I added one to the side of it also. The problem goes away when I hook the constant power for the relay box to the battery vs the harness and the ground stays by the emergency brake like it should be. The interior harness for the aaw only has 2 grounds on it and both are in factory locations with bare metal. The battery is grounded to the block and fender and I have straps from the block to the firewall and frame to firewall. When I tested the ground I think it was right around .3 ohm but def not above 3
 

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Sounds like an inductive spike. When you switch the current through a coil it produces a voltage spike to counteract that change. Clamp diodes are used to suppress the spikes.

When you connect directly to the battery it is able to absorb the spike. When you have a long wire between the unit and battery the battery cannot absorb it as well due to the resistance of the wire.

I have never been too impressed by the wire gauges used in the AAW Classic update kits. The accountants have reduced it to save cost at the expense of performance imho. Same with the crappy $2 headlight switch they supply in their $500 kit.

Don
 

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Discussion Starter #11
Wish I could have seen this kit and painless side by side to help justify the almost double price tag. The 12 gauge constant power wire I used for the dse is also used for 2 other relays that do my door poppers and power door locks. Those relays on the same power wire don’t cause this issue. Would the inductive spike happen due to no diode or a cheap relay inside the dse module?
 

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Wish I could have seen this kit and painless side by side to help justify the almost double price tag. The 12 gauge constant power wire I used for the dse is also used for 2 other relays that do my door poppers and power door locks. Those relays on the same power wire don’t cause this issue. Would the inductive spike happen due to no diode or a cheap relay inside the dse module?
It is hard to say if it is the relays or the actuators themselves. I think either one could produce a spike. Most automotive relays have the diodes so it could be the actuators. Not really understanding why you don’t just connect to the battery directly and move on.

Don
 

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Discussion Starter #13
1. You asked questions so I wanted to respond
2. I like to try and figure things out vs taking the easy route
3. As I said yesterday that after I get the replacement unit from dse if that does the same thing I will run a new power wire to the battery

I posted the question after they said it was going to be $95 to get a new unit. They have since said they will send me a replacement for free. Thanks for all of your help
 

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I don't blame you for researching, testing, and simply asking questions to understand what is required to diagnose an issue. You have my thumbs up.
 

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1. You asked questions so I wanted to respond
2. I like to try and figure things out vs taking the easy route
3. As I said yesterday that after I get the replacement unit from dse if that does the same thing I will run a new power wire to the battery

I posted the question after they said it was going to be $95 to get a new unit. They have since said they will send me a replacement for free. Thanks for all of your help
Don’t take my comment as too negative. I think I gave you a plausible explanation for what is going on. Both Lee and I are electronics engineers so I think you got some pretty good advice here. I’m guessing DSE doesn’t even have an electronics engineer on staff. Based on some responses I got from AAW, neither do they....

Don
 

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Discussion Starter #16
Sorry I was not trying to add tone but after reading it again I can see how it could come off like that. You guys who answer all of our questions are what make this site so great. I greatly appreciate any and all help I can get when I am dealing with issues. Also I could not agree more with your statement on those 2 companies. If I feel like I have more knowledge then the person I am talking to I can only imagine how you guys must feel lol. Thanks again
 

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I personally would also like to know the root cause of the problem. I'm at a point where I'm a little stumped on this one. The 2 second failure is about the same time it takes for the motors to fully open or close the doors so that makes me think it's more of a return current problem with a bad ground. But I was not expecting you to say that the motors run off the headlight wiring. The relay spike combined with long wiring is a reasonable explanation. Perhaps it's a combination of high return current and the relay current spike pushing it over the edge. Here's something you could try. Run the control wire to the battery again, but this time turn on other high current devices like the blower fan to high and see if you get the failure again when you turn on the lights.
 

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Discussion Starter #18
So just went out to check again.

Connected to battery I can not get it to affect the tach no mater what I turn on or do

Connect it to power from aaw harness is the only way I see the issue. I did however look a bit closer since sometimes it is the little things you forget to mention. When it happens I turn on the ignition, then headlights, the tach as the doors are opening makes the tach go neg. after the doors open fully and I hear the relay the tach pops back up to around 500 rpm mark then back to zero since the car is not running. Not sure if that helps or not but at this point I will update the post after I get the new unit and can test. Thank you all for the help
 

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I personally would also like to know the root cause of the problem. I'm at a point where I'm a little stumped on this one. The 2 second failure is about the same time it takes for the motors to fully open or close the doors so that makes me think it's more of a return current problem with a bad ground. But I was not expecting you to say that the motors run off the headlight wiring. The relay spike combined with long wiring is a reasonable explanation. Perhaps it's a combination of high return current and the relay current spike pushing it over the edge. Here's something you could try. Run the control wire to the battery again, but this time turn on other high current devices like the blower fan to high and see if you get the failure again when you turn on the lights.
Ok, I don’t understand why swapping the power source matters if it is a bad ground. But I am also getting a little senile in my old age... :smile2:

Don
 

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Yeah, I guess it really shouldn't make a difference, I'm a bit puzzled on this one. Now I'm starting to wonder if that relay noise is getting coupled onto the tach coil wire somehow. If that tach coil wire runs in the same part of the harness as where you attach the DSE control box then that could explain the needle deflection and also why connecting the control wire directly to the battery fixes the problem. I'll wait and see what happens with the replacement unit.
 
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