Mychron 3 CHT quit working - wild numbers???

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Mychron 3 CHT quit working - wild numbers???

Postby kegracing » Sun Aug 09, 2015 6:21 pm

Robbie and or ALL,

I have a Mychron 3 - 660. Was sent back to Mychron over the winter of 14/15 for firmware upgrades and check out, all good.

Have been running it all summer, 7-8 races, and worked great. Then all the sudden the CHT numbers have gone crazy. Either no number at all, or 1000 degrees and up. EGT numbers seem to still be accurate and fine.

I have checked and trimmed wires on all clamp leads. All wires seem to be good. I have tried a proven CHT ring probe from friend. Same thing. Put mine back on, same thing. No change. Tried flexing all the wires while running, does not help. Have put new batterys in it.

Ideas? Have not found a complete Y cable setup to try yet.. Not sure where to buy stuff either?

thanks,
Ken
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Re: Mychron 3 CHT quit working - wild numbers???

Postby WILD BILL » Sun Aug 09, 2015 11:07 pm

Easiest way to check the Y cable is to plug the CHT sensor into the EGT port and the EGT into the CHT port.

I'd bet one or both wires broke inside the square end of the Y cable. Easy to fix
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Re: Mychron 3 CHT quit working - wild numbers???

Postby kegracing » Mon Aug 10, 2015 12:23 pm

Thanks Wild Bill.

Traveling with work for a couple of days, will try this when I get back... can't remember if i did that already or not.
I did check all the wires, but will look again, especially if switching them works, or shows me anything.

I would much rather have the CHT working than the EGT if I only have one...

thanks again,
Ken
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Re: Mychron 3 CHT quit working - wild numbers???

Postby robbie@aim » Mon Aug 10, 2015 1:04 pm

kegracing wrote:Thanks Wild Bill.

Traveling with work for a couple of days, will try this when I get back... can't remember if i did that already or not.
I did check all the wires, but will look again, especially if switching them works, or shows me anything.

I would much rather have the CHT working than the EGT if I only have one...

thanks again,
Ken


Wild Bill is right, switching the sensors around will let you know if it a continuity problem that can easily be fixed. If the problem follows the CHT sensor then we can assume the issue is on the sensor side of the cable, if it stays on the CHT channel even after switching them then we can assume that the issue is on the Y cable.

Either issue can usually be resolved by disassembling the k-type connection. This is the 2 prong blade connector, male and female. Remove the phillips screws and pop the cover off. under the cover is two additional phillips screws that connect the sensor wire to the connector. Remove the wires and make sure that the wires are not exposed and touching each other. Also make sure that they are not broken. (give them a little tug) If you need to cut the wire back then go ahead, it will not harm the sensor or its output in any way. Make sure to make a mental note about which wire is for + and which is for -. Re-install the wires, making sure they are not touching each other, and replace the cover.

You should only need a pair of wire cutters/strippers and a phillips. Let me know if you have any issues.


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Re: Mychron 3 CHT quit working - wild numbers???

Postby kegracing » Sat Aug 15, 2015 6:31 pm

OK, switched the probes, and it looks like the problem follows the lead - pointing to the Y cable. Car is in the trailer on hanger, so could not crank it, but when swapped I get good number on CHT probe and still getting a 1100+ number on the now EGT probe. When I unplug that lead, it goes to dashes --- no number. Plug it back in, 1100+ number, again with motor off.

Robbie, can you provide a drawing or tell me which pin on the connector to the unit itself go to which wire on the Y cable, etc. I could then check with a meter for each pin to cable end... I have pulled the cover off and checked as instructed, trimmed wires, and do not see a problem.

No race this weekend, but final points race next week, and he is leading the points at the TX Motorplex, so pressure is on (on the tuner) ! :)

Thanks again.

Ken
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Re: Mychron 3 CHT quit working - wild numbers???

Postby WILD BILL » Sat Aug 15, 2015 7:49 pm

I would bet you do have a broken wire inside the square plug. Might not be all the way but enough to raise the resistance value which could be giving you the high readings.

I don't recall exactly which color goes to which blade but it should be fairly easy to figure that out. Or remove the cover from the other plug for reference.

I suggest snipping the wires off the offending plug, stripe back the insulation and reconnect them and see if it works correctly.
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Re: Mychron 3 CHT quit working - wild numbers???

Postby kegracing » Sun Aug 16, 2015 2:24 pm

Thanks Wild Bill

Will trim them, reconnect and try and see.

Ken
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Re: Mychron 3 CHT quit working - wild numbers???

Postby kegracing » Sun Aug 23, 2015 7:14 pm

OK, guys, need help.

Not working. Clipped all the plugs. Checked all the wires, all have good connection.
Pulled the Y-cable. I checked the wire leads to the pins. All seem to be good.
BUT, when I plug either probe into the top temp lead - where I had CHT, it immediately goes to 1100 or so, but not a set number. Unplug it and it goes to blank --- dashes.
I tried to use CHT ring to the bottom lead, but that did not give good readings either.

Tach and playback seem to work fine.

Does this sound like a Y-cable issue or a problem with the unit?

Good news is that we went a few rounds last night, and he won the season points championship at the Tx Motorplex! Now I just need to get this fixed before the Div. 4 Jr bracket finals in 3 weeks.

thanks,

Ken
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Re: Mychron 3 CHT quit working - wild numbers???

Postby WILD BILL » Sun Aug 23, 2015 9:10 pm

Is the issue following the head temp ring?

What happens when the EGT probe is plugged in to either cable lead?
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Re: Mychron 3 CHT quit working - wild numbers???

Postby kegracing » Mon Aug 24, 2015 9:06 am

Either probe gives a bad number on the top. 1100+ If nothing is plugged in, then get the ---.
EGT probe works fine on the botton number position - lead. At ldle, during run, EGT is fine.
Tried putting the CHT ring into the bottom lead, thought it was ok, but numbers did not look right. It did work ok on the log of the run, with CHT ring in bottom. But at idle it flashed around.
I tried a proven good CHT ring lead from a friend, and it did same thing. So looks like the CHT ring is ok.
I have checked all 4 plastic connectors, wires all good. From plug to pin shows good on meter.

Ken
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Re: Mychron 3 CHT quit working - wild numbers???

Postby WILD BILL » Mon Aug 24, 2015 8:29 pm

Sounds like it may have issues outside our expertise then.

See what Robbie has to say about it. Sounds like it may have to go in though.
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Re: Mychron 3 CHT quit working - wild numbers???

Postby robbie@aim » Wed Sep 02, 2015 11:43 am

kegracing wrote:OK, guys, need help.

Not working. Clipped all the plugs. Checked all the wires, all have good connection.
Pulled the Y-cable. I checked the wire leads to the pins. All seem to be good.
BUT, when I plug either probe into the top temp lead - where I had CHT, it immediately goes to 1100 or so, but not a set number. Unplug it and it goes to blank --- dashes.
I tried to use CHT ring to the bottom lead, but that did not give good readings either.

Tach and playback seem to work fine.

Does this sound like a Y-cable issue or a problem with the unit?

Good news is that we went a few rounds last night, and he won the season points championship at the Tx Motorplex! Now I just need to get this fixed before the Div. 4 Jr bracket finals in 3 weeks.

thanks,

Ken


Ken,
You can find the pinout for the y-cable at: http://aim-sportline.com/download/doc/eng/mychron4_2t/Cavo_MyChron4-2T_2Termocoppie_100_eng.pdf. If you find that the cable has good continuity then please box up the 660, y-cable, and temps sensors and ship it to me. I will be happy to take a look at them.
31889 Corydon St. Suite 130
Lake Elsinore, CA 92530

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Re: Mychron 3 CHT quit working - wild numbers???

Postby kegracing » Fri Sep 04, 2015 3:09 pm

Thanks Robbie.

I will double check cables. Will have to run as is next weekend for the Div. 4 finals, at least the tach works. Will not do any major tuning changes.

Will then get back with you if still having issues, and let you take a look at it.

Ken
A country boy can survive... but the same can not always be said for those who cross him or his family!
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Re: Mychron 3 CHT quit working - wild numbers???

Postby kegracing » Fri Mar 11, 2016 1:14 pm

Robbie,

I sent the tach to you, along with the cables, as requested. Will try to call and touch base with you also.

Tried fresh battery. I also swapped cables with a set off of another car that were working. Same issue with known good cables, and my cables worked on the other car. Been busy, and now behind, like normal.

Not sure what is wrong. Need your assistance.

thanks for the help,

Ken
A country boy can survive... but the same can not always be said for those who cross him or his family!
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