Bad Starter Relay?

[db1yg]

Hi Steve,

Agree with others--sounds like a bad battery. Put your volt meter on the battery, crank the engine, and note the voltage. I bet it will drop to 10 volts or less--even though it will read 12.4 or better without a load. About a year ago I got two bad new PC680's in a row. Between the first and second "new batteries" I thought it could not possibly be the battery since it was brand new, so I replaced both the master and starter solenoids---same problem. Then I learned you must "load" the battery to test--the "new" battery dropped to 10- volts. It, like the first, was tested and replaced by the vendor but it cost me time and taught me a lesson.

Cheers,

db

[RKellogg]

Sudden development of the problem makes me think that there is a loose or corroded connection in the starter loop. Check ground leg, too.

[ClayR_9A]

The same thing recently happened to me... haven't had a problem starting for a long time. Went flying, then landed and fueled up, and then just a click and a strange whine.

Bought and installed a new PC 680 battery. Exact same problem.

Bought and replaced the solenoid on the SkyTec starter (bought at auto parts store)... same problem.

Ordered a new starter relay from Vans -- still in my car, yet to install it yet, but I'll bet that's going to fix it.

Wish I knew that it was available at an auto parts store or I would have bought it at the same time. It looks exactly the same to me.

[Mich48041]

Slow or no cranking is caused by low voltage. Low voltage can be caused by a bad (or uncharged battery) or by a bad connection. A bad connection will have the same symptoms as a bad battery. A rapid clicking or chattering contactor usually indicates that the problem is the battery itself or a bad connection somewhere between the battery and contactor in either the positive or negative current path. Chattering does not mean that the contactor is bad. However, chattering could lead to premature contactor failure. Sometimes a bad connection will release a small amount of smoke when heavily loaded, as when engine cranking. And sometimes a bad connection will be warm to the touch. If a bad connection can not be found by observation, it can be found by measuring voltage drop while the circuit is heavily loaded. It is safer to disconnect the starter motor and to substitute another heavy load, perhaps an automotive headlamp. Headlamp current, being less than starter current, will allow longer voltmeter testing before the battery is depleted. A large voltage drop indicates high resistance from a bad connection.

[alpinelakespilot2000]

Indirectly, the battery seems to be the issue. However, after charging the battery up and getting the plane started, I found that my alternator was showing zero amps on my ammeter, which on my setup shows alt output. I checked the alt field breaker (ok), the big starter and alternator cables (ok), then tried the plug in the back of the Plane Power alternator. All 3 little wires, including their molex pins were loose, somehow having backed most of the way out of the plug! So, it seems that sometime on my last flight that alternator connection had failed, shut the alt down without me knowing it, and drawn the battery down just sufficiently to prevent the starter from having enough power today. Will have to figure out why my Dynon didn't warn me, maybe I had that warning turned off for some reason.

Thanks for the help so far. Will report back when I confirm things are back to normal.

[PCHunt]

Per Bob Nuckolls, voltage is what you should monitor/alarm. Amps don't really matter. A properly charging alternator should be putting out 13.5+ volts. A battery under even mild load will put out around 12.5 volts, and less as time goes by after an alternator failure.

So if you have a "low voltage" light, or EFIS warning, it should be set to warn at around 13v or so. I like a BIG RED LIGHT in my face for low voltage,( and low oil pressure). I want to know the instant the alternator fails, so I can take appropriate action.

B and C has one, as does Eric Jones at Perihelion designs.

YMMV

[ClayR_9A]

Originally Posted by ClayR_9A

The same thing recently happened to me... haven't had a problem starting for a long time. Went flying, then landed and fueled up, and then just a click and a strange whine.

Bought and installed a new PC 680 battery. Exact same problem.

Bought and replaced the solenoid on the SkyTec starter (bought at auto parts store)... same problem.

Ordered a new starter relay from Vans -- still in my car, yet to install it yet, but I'll bet that's going to fix it.

Wish I knew that it was available at an auto parts store or I would have bought it at the same time. It looks exactly the same to me.

Update - I installed the new starter relay - same problem.. So, now I have a new battery and new starter relay and new starter solenoid. Today, I sent my starter back to SkyTec. (It is the 149-12LSX model that they don't make any more, so I'm guessing I'm going to end up with something else)

Here's another piece of information that I discovered while changing the starter solenoid... I had the diode installed BETWEEN the S and I terminal and had a wire from the I terminal going straight to ground.

I've been flying for 11 years now and that didn't seem to be a problem, but as I look at the wiring diagrams, it obviously isn't correct. I really don't know how this didn't trip a fuse because it should be a short from the start switch. There must be some resistance out to that I terminal.

I changed the diode to go from S to ground and I is disconnected. Same symptom though.. still doesn't start.

EDIT: I also found this post http://www.vansairforce.com/communit...9&postcount=36 which leads me to believe that maybe the inside connection to the I terminal shorted out long ago so maybe it was still more or less working the same way since there was a path to ground through the diode from the S terminal. Interesting that someone else had their starter relay wired the same way as I did.

[erich weaver]

Originally Posted by PCHunt

Per Bob Nuckolls, voltage is what you should monitor/alarm. Amps don't really matter. A properly charging alternator should be putting out 13.5+ volts. A battery under even mild load will put out around 12.5 volts, and less as time goes by after an alternator failure.

So if you have a "low voltage" light, or EFIS warning, it should be set to warn at around 13v or so. YMMV

Yes, if you were forced to monitor either voltage or amps but not both, you would go with voltage as it provides good information on the overall health of the electrical system. Amp readings are useful however; if you turn on your strobes or other electrically driven device and you dont see a rise in your amps, they are likely not operating. Also, abnormally high or low amp readings are idnicators that you may have inadvertently left something on or failed to turn something on.

With respect to the setting for the low voltage light, be aware that a voltage reading at an EFIS or engine monitor may be somewhat lower than the available battery or bus voltage. EFISs commonly have multiple power inputs requiring voltage lowering diodes to be present to prevent power applied to one input flowing back out of the EFIS through a 2nd power input terminal. Thus while everything can be fine and dandy with 14+ volts at the battery or bus, your EFIS reading may be only 13.5 and perfectly normal. Clearly what you want to be aware of is the abnormal condition and have your warning light limits set to identify that.

regards
erich

[Rosie]

I learned many, many years ago that as a rule of thumb, with a GOOD battery, you should see 10v or more while cranking Rosie

[Mich48041]

Went flying, then landed and fueled up, and then just a click and a strange whine.

That strange whine might have been the starter motor spinning without the gears engaging.