Intermittent high amperage

[gras747]

Amps spike to the redline and cause engine warning then immediately return to normal.

No breakers tripped

No smoke

Anyone?

[Tom Baker]

Check you grounds, and clean the connections on the shunt. 

[gras747]

Thank you

Will do

 

[Garrett Gee]

4 hours ago, Tom Baker said:

Check you grounds, and clean the connections on the shunt. 

Second this.  This seems to happen to me about every 12-18 months, and cleaning the small wires to the shunt and hitting them with a little dielectric grease has always worked for me.

[cdarza]

Every now and then the grounds/connectors need to be inspected and cleaned.   I recently have the CHT/OIL temps going from green to red when i PTT.   Usually the cleaning keeps this from happening for about a year.  

[Animosity2k]

On 10/2/2023 at 7:38 PM, garrettgee2001 said:

Second this.  This seems to happen to me about every 12-18 months, and cleaning the small wires to the shunt and hitting them with a little dielectric grease has always worked for me.

What is a shunt?

[Anticept]

A super low resistance bridge. It causes a tiny bit of the electrical flow to go into an ammeter without actually splicing it directly into the wire.

They look like this:

 

Below is the "water analogy" and a simplified electrical schematic:

[gras747]

I cleaned the 4 shunt connections and flew for 2 hours with no problems then the GREMLINS came back to haunt.  Both ammeter leads to the shunt have fuse holders that I cleaned the fuses also.  Why are these neccesary ?   I also cleaned all the stab connectors on the terminal block on the firewall behind the RH panel.  I don't have a schematic (any help there???) but do I need to start at the battery negative terminal on the engine side of the firewall and clean and treat every connection?  Yikes!

[gras747]

In re-reading my post I think I know that these fuses are to protect the Dynon ammeter in case there was some kind of surge of current from the shunt. IE a failed shunt

[FredG]

Those fuses prevent the ammeter sense wires from burning up if one were to short to ground (should the insulation abrade) or if either wire came loose from the plug into the Dynon and shorted to ground.  There is no other protection for them.