Ovation battery problem

[rgpilot]

Battery 2 not supplying power. Checked battery and found it fully charged. Battery 1 powers Master. I'm thinking a solenoid problem or a battery switch problem. I checked battery terminals and solenoids connections and found them tight. Any thoughts on best way to diagnose problem?

[carusoam]

Clicking the battery selector switch triggers the loud solenoid…

Might need a second person up close to listen or use a volt meter…

Could be an old relay has gotten tired… may need some exercise…

Tap on the relay gently to see if it moves?

PP thoughts only, not a mechanic…

Best regards,

-a-

[mike_elliott]

THere is a battery switch relay in the radio bay that has a tendency to fail when switched often while engine running in some of the older M's and O's. Put this in your items to check.

 

[rgpilot]

I think I have found the problem. 10 amp slow blow fuse leading to solenoid for battery 2 was blown. I haven't replaced it yet but one is on order.

[atpdave]

Looking at the electrical schematic diagram for SN 29-0317 (800383 R7) the only 10A fuse connected to Master Relay #2 is for the trickle charge circuit.  It doesn't control the relay.  The wire that controls the relay is attached to Terminal 85, the small terminal that is farthest from the mounting bracket according to the relay drawing.  That wire goes to the battery selector switch, which is connected in series to the master switch, the other terminal of which is connected to a grounding plug.  There is no fuse in that circuit.  All it does is provide a path to ground for the battery relay coil.  The other side of the coil is connected to the battery through a jumper wire.  My bet is a loose or broken wire or bad connection in that circuit.  I've attached a couple of drawings for your reference.  You can test the relay by grounding terminal 85.  For safety I would put a fuse in the test lead.  You definitely don't want to ground the hot side by mistake!

The reason that 10A fuse is blown is most likely from a drawn-down battery sucking a high current through the trickle charge circuit sometime in the past.

Pages from MAN161.pdf Battery Relay Kissling 26.57.01.pdf

[Mufflerbearing]

All good information here.  I had a relay switch fry.  Simple to hear it or not hear it switch.  Follow up with voltage testing to verify.  Parts available and easy to replace, under the direction of your mechanic.

[rgpilot]

Thank you atpdave. That will be a great help in trouble shooting. I did have a very low battery 1 some time ago and your explanation makes sense.

I will ground terminal 85 and go from there. Maybe just a bad solenoid.

[rgpilot]

After further investigation I found that the blown fuse was a 10 amp fuse coming off terminal 85.  I see that it doesn't show in the wiring diagram. The fuse in the wiring diagram is a 1 amp fuse (Littel 313001) coming off terminal 88A.  Maybe they added the fuse and didn't update the wiring diagram. I'll replace it and see what happens.

[atpdave]

4 hours ago, rgpilot said:

After further investigation I found that the blown fuse was a 10 amp fuse coming off terminal 85.  I see that it doesn't show in the wiring diagram. The fuse in the wiring diagram is a 1 amp fuse (Littel 313001) coming off terminal 88A.  Maybe they added the fuse and didn't update the wiring diagram. I'll replace it and see what happens.

That is confusing.  The only 1A fuse I can find anywhere on that schematic is connected to the Starter Relay (mislabeled a solenoid on the schematic) and it feeds the START POWER annunciator circuit.  It is attached to terminal 88a but although it is the same type, that relay is not Master Relay #2.  If you see another 1A fuse on the schematic I’d appreciate knowing where it is.  How many wires do you see attached to Master Relay #2 terminal 85?  If there is more than one, then it is likely that something has been miswired and it could also explain the blown fuse.  Does the blown-10A fuse holder still have a label, and if so, what does it say?

It is unlikely that the battery selector circuit has an undocumented modification by the factory since schematics for later M20Rs are essentially the same with respect to that circuit.

[rgpilot]

I didn't see a label on the blown fuse holder. I'm not sure about the other wires on terminal 85. I don't think there were any others attached but I will look further next time I get to the plane.

[thinwing]

it is likely the relay it self....a german produced design..i think I read that Maxwell has replaced them with more reliable relays for cessnas etc

[LANCECASPER]

On 7/26/2021 at 9:00 AM, rgpilot said:

After further investigation I found that the blown fuse was a 10 amp fuse coming off terminal 85.  I see that it doesn't show in the wiring diagram. The fuse in the wiring diagram is a 1 amp fuse (Littel 313001) coming off terminal 88A.  Maybe they added the fuse and didn't update the wiring diagram. I'll replace it and see what happens.

Sounds like they did the Service Bulletin (M20-275) or maybe yours was made after the Service Bulletin and it came that way from the factory, but you looked at an older schematic before the SB.

 

 

 

https://www.mooney.com/wp-content/uploads/2020/12/SBM20-275.pdf

 

 

[rgpilot]

Purchased a new Kisslling 26.57.01 relay for $484.00 from Peerless Electronics. Buying from Mooney would be about twice that for the exact same part.

[StevenL757]

25 minutes ago, rgpilot said:

Purchased a new Kisslling 26.57.01 relay for $484.00 from Peerless Electronics. Buying from Mooney would be about twice that for the exact same part.

Unless Mooney lowered the price, those Kissling relays are about $1250 from the factory at last look.  I live 15 minutes from Peerless on Long Island, and have ordered several of them in the past...for myself, and other members over the last 10 years.  I remember paying $453 for mine a few years ago, so the price increase hasn't been unreasonable.  Peerless was good to work with.

[atpdave]

6 minutes ago, rgpilot said:

Purchased a new Kisslling 26.57.01 relay for $484.00 from Peerless Electronics. Buying from Mooney would be about twice that for the exact same part.

I hope that solves it for you.  At the risk of stating the obvious, disconnect the #2 Battery before doing anything else.

[rgpilot]

I'm sure I could do the work myself, but I work with an excellent A/P mechanic who will do it for me. I'm sure he will disconnect the battery and possible remove it to give better access.

Thanks for everyone's help. It's great to have this resource to help solve problems.