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Old 11-02-2019, 07:33 PM
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DA Sensor Resistance

Playing with a hard to start DA100 that has about 400 flights on it and has been very reliable up until now. Main issue appears to be intermittent spark. Without getting into a long story does anyone know what an acceptable resistance measurement should be on a DA red (coil) pickup ?? I am waiting for a call back from DA but not likely going to happen until next week.

I measure the resistance on my sensor as 590 ohms. Have checked it with several digital VOM's. All within about 6 ohms of each other.

The FAQ for no spark on the DA site indicates sensor resistance should be above 169 ohms. But I do not know what normal range would be ie is 590 too high ??

I can hang a small screwdriver off the hub magnet so that seems fine. Unfortunately I do not have a spare sensor or I would swap it and try it. I have swapped the ignition to a known good one that I flew all summer.

I expect DA will call me next week but just looking for any quick answers if anyone has one. Thanks
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Old 11-02-2019, 08:36 PM
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I have no clue what the resistance should be but my new DA spare measures 254.3 ohms.
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Old 11-02-2019, 08:44 PM
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Originally Posted by Truckracer View Post
I have no clue what the resistance should be but my new DA spare measures 254.3 ohms.
Thanks for that. I have searched and read older posts about sensor issues and at least one mentioned mid 200's as being normal, but I have no idea if there is an upper acceptable limit. When I tested mine and got 590 I wondered if that was too high, but I have no idea.
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Old 11-02-2019, 09:17 PM
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That is a considerable resistance difference for a coil of wire. The only way I've tested DA sensors is by substitution with a known good one.
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Old 11-02-2019, 09:30 PM
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Originally Posted by Truckracer View Post
That is a considerable resistance difference for a coil of wire. The only way I've tested DA sensors is by substitution with a known good one.
That was my initial reaction but I do not know whether that indicates a problem in the coil sensor or not. When I saw the FAQ indicate more than 169 and mine is 430 ohms more than that I wondered if that was indicative of a problem. I have two other DA150's but I would have to take the cowls off and mess around to get at the sensor plug and I was trying to avoid dismantling other engines etc.

I also wondered if that might mean a partial break in the sensor wire lead but I am reluctant to cut the red shrink tube off to see what the wire looks like. If DA tells me there is something wrong with it then I will cut the red cover tube off for my own curiosity. I am going to order a new sensor but it will take several weeks to get it.
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Old 11-04-2019, 01:03 PM
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A few years back I had the hardest to start DA 150 in the SE United States. We went tuned the carb, new plugs, checked compression - nothing seemed to help. Then I borrowed a red sensor from a well starting/running DA installed it and tried to start it. Bam, it popped on the third flip! Choke off, throttle trim up three clicks and flipped the prop! Started on the third flip. This engine ran like a champ from then on especially since we had "specked" it!! Moral of the story is that the original sensor was bad!

Change or borrow a sensor from a well running DA and you will be in business. BTW all DA sensors are the same!
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Old 11-04-2019, 06:10 PM
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Change or borrow a sensor from a well running DA and you will be in business. BTW all DA sensors are the same!
I am hoping that a new sensor will help rectify the problem. Just on hold waiting for DA to call me about the ignition I sent in. Hopefully they will tell me the ignition is fine and when they send it back to me I can order a couple of spare sensors - one to fix the problem and one to have on hand in case one of my other DA's ever shows similar symptoms.
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Old 11-04-2019, 08:49 PM
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I just measured a DA sensor off a 120 and it read 250 ohms.

DA uses an inductive coil instead of a hall sensor, so frankly I wouldn’t worry about 590 ohms since they said anything above 169 is OK.
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Old 11-05-2019, 01:18 PM
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Originally Posted by billpilotca View Post
I am hoping that a new sensor will help rectify the problem. Just on hold waiting for DA to call me about the ignition I sent in. Hopefully they will tell me the ignition is fine and when they send it back to me I can order a couple of spare sensors - one to fix the problem and one to have on hand in case one of my other DA's ever shows similar symptoms.
That's what I have done too! I also ordered some carb kits just in case i need them!
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Old 11-05-2019, 05:17 PM
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Quote:
Originally Posted by jack01 View Post
I just measured a DA sensor off a 120 and it read 250 ohms.

DA uses an inductive coil instead of a hall sensor, so frankly I wouldn’t worry about 590 ohms since they said anything above 169 is OK.
Thanks to all for feedback and especially those who took the measurements. I decided I had to remove the cowl from one of my 150's so I measured the sensor and got 251 ohms. Based on feedback here it seems mid-200's is pretty normal.

I appreciate that the FAQ said anything above 169 is fine but I still have to wonder if a sensor measuring more than twice the normal resistance indicates a problem in the coil or wire.

Still waiting for a call from DA re my ignition but I expect that they are backed up. Supposed to get snow here this week so I may have lots of time to figure this out.

I also have a question as to what the location of the sensor should be on the hub. Not that I have ever intentionally moved it but mine is what I would describe as mid range in the adjustment for the DA100. Hope that location is about right.
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Old 11-05-2019, 05:40 PM
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On your sensor there is a raised embossed line in the front.When engine is at TDC that line needs to be lined up with the leading edge of magnet.
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Old 11-06-2019, 04:57 PM
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On your sensor there is a raised embossed line in the front.When engine is at TDC that line needs to be lined up with the leading edge of magnet.
Thanks, the pickup sensor is off the engine at the moment but I think I see what I would call a raised ridge on the front, that , if it was on the engine, would be a few mm in front of the metal point of the pickup.
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Old 11-06-2019, 06:31 PM
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You got it,the way DA moves these around seems any where in the adjustment slot they run.
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