Battery Relay not Engaging

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ahazi
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Battery Relay not Engaging

Post by ahazi »

Yesterday about to take off from Santa Paula (KSZP) with my 2005 DA40, G1000, I received an annunciation on the G1000 that the ADS-B is not functioning. With a VP TFR north of KSMO I did not want to fly without ADS-B.

I tried doing the following while the engine was running:
1. Cycled the avionics switch - no success
2. Pulled out the transponder circuit breaker - no success
3. Turned off the battery switch so the whole system will reboot - big failure!

Nothing electrical is working now except the cabin lights above (the ones that if you forget to turn off will drain your battery completely...).

The battery is testing good, 25.1 volt.
Seems like the battery relay is not engaging. Does anyone have experience with a failed battery relay or a failed battery/alternator rocker switch? Could it be something else? First time ever in 13 years of owning this a/c that I am having an electrical problem other than replacing the alternator 3 years ago.

A/C is AOG in Santa Paula and I am back home near Santa Monica. Trying to figure out what might have gone wrong.

Thanks,
Ariel
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haykinson
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Re: Battery Relay not Engaging

Post by haykinson »

This is not your question, but the ADS-B Failure message is a frequent transient failure when you are low to the ground. It seems like some areas cause it consistently (I get it about one in five times when maneuvering to land at SMO). Maybe it means you stop receiving any data from nearby towers, or something along those lines. I’ve learned to ignore it, and it usually clears after ten to thirty seconds.

I think you can bypass the master switch — one of the circuit breakers will bypass it and turn your system on. I think it’s the one called Master Control.
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ahazi
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Re: Battery Relay not Engaging

Post by ahazi »

Thanks Ilya,

I have seen this ADS-B message before and it went away but with the TFR north of KSMO I was very cautious. Obviously something broke in the process of restarting the system.

Not sure what you mean by:
haykinson wrote: Sat Jun 26, 2021 4:26 pm I think you can bypass the master switch — one of the circuit breakers will bypass it and turn your system on. I think it’s the one called Master Control.
I looked at the schematic and it seems that the BATTERY switch grounds the battery relay coil and engages the contact. It was getting dark and I did not have tools with me to investigate further.

Are you based in KSMO? Do you feel like flying to Santa Paula?

Ariel
Last edited by ahazi on Sat Jun 26, 2021 6:02 pm, edited 1 time in total.
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haykinson
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Re: Battery Relay not Engaging

Post by haykinson »

Update: I was wrong in my memory and my interpretation of the schematic. Not sure why I remember suddenly turning electrical things on with circuit breakers.
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Re: Battery Relay not Engaging

Post by ahazi »

Update: I flew to KSZP and checked the a/c more closely on Sunday. Big THANK YOU to Ilya for flying me and helping to diagnose the issue.

Here are the facts:

1. The BAT switch is good
2. The circuit to the relay coil is not broken
3. The BAT relay has 2 coils, one (high current) for initial pull that get disconnected (NC internal contact) after engaging, second (low current) coil that holds the relay engaged. The 2nd coil circuit is in place but the first coil/contact are not working and therefore the relay cannot be activated.
4. The relay is covered and located on plate/bracket on the firewall and I don't know how to open and remove the cover as everything is VERY tight. How is this relays plate get accessed, seems like an impossible task without removing parts of the engine... The access is blocked by the engine mount

I am looking for ANY experience from forum members about accessing and replacing the BAT (battery) relay.

I think I can do something to get power temporarily (using the EPU relay with existing battery) so I can fly the a/c to a Diamond shop for proper repair.

Any help or ideas will be greatly appreciated.

Ariel
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Steve
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Re: Battery Relay not Engaging

Post by Steve »

You can get the cover off, but as you noticed, it ain’t easy. I had to replace the starter relay about 17 years ago, and I remember cursing a lot during the process. I vaguely recall that there are two metric bolts that hold the cover in place, and that the cover is slotted to fit under them. So, you don’t have to completely remove the bolts, just loosen them. Then you have to work the cover off between the engine mount and the relay chassis. Like I said, lots of cursing.

Also, don’t forget to disconnect your battery before starting work….

Good luck.
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Re: Battery Relay not Engaging

Post by ahazi »

Steve wrote: Mon Jun 28, 2021 5:45 pm You can get the cover off, but as you noticed, it ain’t easy. I had to replace the starter relay about 17 years ago, and I remember cursing a lot during the process. I vaguely recall that there are two metric bolts that hold the cover in place, and that the cover is slotted to fit under them. So, you don’t have to completely remove the bolts, just loosen them. Then you have to work the cover off between the engine mount and the relay chassis. Like I said, lots of cursing.
Thanks Steve,

What is the serial number of your DA40?
Is it equipped with a G1000 system?

There might be differences in the physical setups as the DA40 design evolved (or maybe deteriorated from a maintenance aspect) over time. My a/c SN is 40.479 with G1000.

I removed the pilot side screw of the relays cover, that side is not slotted. The other side might be slotted but still, I see no way of removing the thin fiberglass cover of the relays assembly short of cutting it.

Ariel
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Steve
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Re: Battery Relay not Engaging

Post by Steve »

Mine is an early one: 40.049, and was built in Austria, not G-1000. So you are correct in that there could be some differences. The composite cover can flex a bit which allowed (at least in my case) working it out and allowing access to the relays.
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Charles K
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Re: Battery Relay not Engaging

Post by Charles K »

On the ADS-B fail - that also sometimes happens on the ground with low voltage at low RPM.

If you have a shore power supply and the proper ground plug (Cessna type three pin) for your ground power plug on co-pilot side under the hatch, if you plug shore power in that will also energize the relay. Easy way yo see if the relay is good and something else is amiss. That third little pin on that plug is for just that purpose - to energize the relay.

Best of luck on diagnosis.
Charles
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ahazi
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Re: Battery Relay not Engaging

Post by ahazi »

Charles K wrote: Tue Jun 29, 2021 12:48 am If you have a shore power supply and the proper ground plug (Cessna type three pin) for your ground power plug on co-pilot side under the hatch, if you plug shore power in that will also energize the relay. Easy way yo see if the relay is good and something else is amiss. That third little pin on that plug is for just that purpose - to energize the relay.
I did something similar to test the situation. I enabled the EPU relay by connecting the small EPU pin to the positive battery post, it clicked, the battery is good, the EPU relay is good. By connecting the big plus pin of the EPU plug to the positive terminal of the battery I can use the EPU relay as a temporary replacement for the BAT relay. I will hook a switch with a long wire between the battery and the small EPU pin and bring it into the cockpit so I can have an alternate method to power the plane and get it to a shop.

This is my plan, comments are welcome.

Ariel
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