Should I replace my tach generator

[PMcClure]

My Ovation 2 is going into annual next week. I have had an intermittent problem with the tach not working. I have had the Avionic shop chase it down, replaced connectors, etc...It just goes out sometimes and works others. A new generator is $1200 (TCM part no. 653141). I can't be sure this will fix the problem. Any suggestions before we just spend $1200 plus labor to "see" if it fixes the problem?

 

 

[carqwik]

I put the EI tach in my Bravo in the 2" hole where the OE part went...works great.  I think it was $500 for the tach plus labor...

[N201MKTurbo]

I have had both Horizon and UMA electronic tach's. Both were rock solid and both cost about $500

[PMcClure]

Thanks Carqwik, but I don't think this is a good option for me. The Ovation has the smaller under dash engine gauges. I think the factory tach is probably required equipment too. 

[N222VS]

We have the very same problem with the tach in our 02. Our annual isn't due until march and we were going to look into a tach generator overhaul?? I don't know if overhaul is available but we have pretty much narrowed it down to the tach generator. We have been having issues since we purchased in 06 , & it is getting worse as of late. We have sent inst cluster off for bench test & checking history in log book so did the previous owner & it checked out OK.

Our issue seems to be time/temp related usually either on long climb to 10-14k ft it will just go crazy "needle straight down & #'s way out of wack" but after level off when things start cooling down it will slowly come back in & then about the 1 hr in cruise it will start acting crazy again.... Very interested in what you find!

[PMcClure]

http://mooney.free.fr/TCM/SB02-3.pdf

[N222VS]

Perfect , thanks

Is $ 1200 the best price you have found??

I'm going to check the #'s ASAP & get that rolling

Thanks again!

[PMcClure]

Perfect , thanks

Is $ 1200 the best price you have found??

I'm going to check the #'s ASAP & get that rolling

Thanks again!

Haven't looked much but will this week. I'll report back what I find. 

[Marauder]

Thanks Carqwik, but I don't think this is a good option for me. The Ovation has the smaller under dash engine gauges. I think the factory tach is probably required equipment too.

The EI tach is legal to be primary. Reading over the service bulletin you posted, it is to address an issue with the tach magneto sensor. The EI tach obtains it's information the same way.

[carusoam]

Since it appears to be temperature sensitive and the sensor part is on the engine. That makes sense. The instrument in the panel is digital with an analog needle.

I would expect to have to replace the parts mounted on the engine, not so much the parts in the ( temperature controlled) panel.

PMc, Thanks for posting the service bulletin. That was very helpful!

Best regards,

-a-

[PMcClure]

I agree the problem is most likely not the original tach or panel. It is most likely the sensor on the mag (even more likely since I found the service bulletin. Could be a connection, but the wiring has been replaced/checked many times. My issue is not temp. related. The best description is "erratic". It can work or fail at start-up, taxi, cruise or decent.  The real question becomes how many hours does my engine really have since this is probably an issue since it left the factory. 

[tascher]

"The real question becomes how many hours does my engine really have since this is probably an issue since it left the factory."

I had a few flights in my Ovation 2 a couple of years ago with the same symptoms; tach readings which, if real, would have spelled the end of my engine and Hobbs readings significantly higher than expected. The Air-Mods guys @ N87 traced it to a connection behind the ignition key. All tach and Hobbs readings have been normal since they repaired the connection.

I have had the 310hp upgrade installed since those bad readings and subsequent repair. The STC requires a 2700rpm primary tach, for which I'd believe both the horizon and the EI are certified. I called Moritz about the possibility of having the original equipment tach recallibrated and relabeled for 2700. They couldn't/wouldn't do it unless they recertified the entire instrument strip. If every single Ovation, Bravo, and Eagle driver with Moritz strips banded together and said lets do it, maybe Moritz would take the bait. So now I've got an EI.

The Moritz consistently reads 20 to 40 rpm higher than the EI, but they are both counting pulses from the same junction behind the ignition switch - I watched Matt at Midwest Mooney wire the EI. All of which is a long-winded way of saying that there's a lot going on back there at that connection. If I were checking connections related to the tach, I would have started at the engine. Maybe it's obvious to everyone else, but the ignition switch connections wouldn't have made the list. Make certain that they've been checked before springing for a new tach or tach generator.

[carusoam]

There are definitely nicer tachs available. They even calculate rpm drop during run up. My interpretation and math skills are good, but slow...

I kept the OEM tach, recalibrated and repainted. Looks original and occupies the same small orifice.

2700 rpm is the nice part. How you read it is somewhat optional.

Best regards,

-a-

[Cruiser]

There are definitely nicer tachs available. They even calculate rpm drop during run up. My interpretation and math skills are good, but slow...

I kept the OEM tach, recalibrated and repainted. Looks original and occupies the same small orifice.

2700 rpm is the nice part. How you read it is somewhat optional.

Best regards,

-a-

Pictures would help......

[carusoam]

Tom,

I'll try, but I'm a couple days from being able.

Best regards,

-a-

[PMcClure]

There are definitely nicer tachs available. They even calculate rpm drop during run up. My interpretation and math skills are good, but slow...

I kept the OEM tach, recalibrated and repainted. Looks original and occupies the same small orifice.

2700 rpm is the nice part. How you read it is somewhat optional.

Best regards,

-a-

 

 

There are definitely nicer tachs available. They even calculate rpm drop during run up. My interpretation and math skills are good, but slow...

I kept the OEM tach, recalibrated and repainted. Looks original and occupies the same small orifice.

2700 rpm is the nice part. How you read it is somewhat optional.

Best regards,

-a-

But if the problem is the tach generator, I would still have the same problem even if I replaced the tach with a new one? Does the tach generator come with the new tachs?

[Marauder]

Does your tach look like this? If so, I can understand why you are struggling for a solution. Your tach and MP are integral to the panel and changing it out to aftermarket gauge would require installing the replacement somewhere else in the panel. If you want to maintain the current integrated gauge, unfortunately I think you are stuck going down the path you are on.

[PMcClure]

Does your tach look like this? If so, I can understand why you are struggling for a solution. Your tach and MP are integral to the panel and changing it out to aftermarket gauge would require installing the replacement somewhere else in the panel. If you want to maintain the current integrated gauge, unfortunately I think you are stuck going down the path you are on.

 

 

Does your tach look like this? 

That is the same set-up (some funky readings on that picture!!). Looks like my plan is to order the $1200 part and check the ignition switch connection Tascher mentioned before installing it.

[carusoam]

PMc...

Sorry, That's my version of thread drift...

Sounds like the tach generator is the issue. But, if your are considering the 2700rpm "upgrade". You can consider both ends of the rpm gauge system (generator and indicator).

Anything that works sometimes and not another is worthy of checking all related connections.

Best regards,

-a-

[N601RX]

But if the problem is the tach generator, I would still have the same problem even if I replaced the tach with a new one? Does the tach generator come with the new tachs?

The EI tach does not use a tach generator. It hooks directly to the P Lead on the Mag lead through a resistor.

[carusoam]

As far as Hobbs time in Ovations.....

My Hobbs meter is in the baggage area and probably actuated by an oil pressure switch. It's electric and actual time. Not rpm related.

My C had the hobbs on the rpm gauge. The tach "generator" was a spinning cable off the back of the engine. Much easier to verify.

Best regards,

-a-

[PMcClure]

Update - out of annual and replaced the tach generator. We found a replacement for about $900. I have done three tests runs and it seems to be working fine.