Accord 93 TCU went bad again

[orangeclockwork]

Hello guys
I am new in the forum, so following the rules I wont post this question on the thread I would like to, http://www.cb7tuner.com/vbb/showthread.php?t=185004

I live in Argentina, and I have recently bought a 93 Accord EX A/T, in very nice condition which drove fine for a couple of weeks until its D4 light came up and stayed lit no matter the position of the lever.
The only available gears were 2 and D4, if shifted manually.

So I have done the DIY rebuilt found here http://www.cb7tuner.com/vbb/showthread.php?t=185004 with great care on soldering, and voila! the car drove smooth and fine for 3 or 4 days, until the D4 light came on again.

Opened up TCU again and found the two resistors with blackish aspect as a sign of overheated.

Replaced again the 2 resistors, and just in case C28 diode for a new one.

Yesterday, put everything back on and the car drove fine again....for just a couple of hours, I did not open TCU again but I suspect it is all over again the same.

The question is, could it be any other component inside the TCU the culprit of the burnout or should I look for somewhere else? maybe solenoids?

Just after buying the car I replaced the ATF twice (3 quarters Honda ATF each time) just to be sure I wont have any AT issues, never expected a problem like this...

Hope anyone can help or give me a clue.
Thanks in advance
Julian

[Jarrett]

Julian, I'm not very familiar with TCU issues as I try to stay away from automatic transmissions in general. But I would like to thank you for conveying your issues and the measures you've taken to rectify them in a clear, concise manner. All too often it seems that people who live here and claim to speak the language can't get out of their own way to put their thoughts into text without filling it with Internet abbreviations, slang and spelling/grammatical mistakes. To be from Argentina and still have a firm grasp on the English language and forum ettiquette is a welcome respite. Thank you.

[illinois_erik]

Perhaps higher wattage resistors are in order

[Bad_dude]

I have a little electronic background, but your resistors blew most likely due to bad capacitors. Bad capacitors will shunt too much current through the resistors and blow the resistors. Replacing the resistors alone won't help you as they will blow again. You need to trace the path of the resistors back to where they flow. I would replace all of the capacitors with a little bit of higher ratings, higher uF and volts. The older board tend to have higher resistance.
My advice would be to replace the 5 capacitors with good brand names if possible like Nichicon. If not, find capacitors that at least have the brands on them for quality.
The 2nd option would be, to find another TCU, then replace all 5 of the capacitors, then install it. Leaking or blown capacitors are not always shown on the top, look on the bottom and some time they will leak there.

Good luck and keep us updated.

[orangeclockwork]

Julian, I'm not very familiar with TCU issues as I try to stay away from automatic transmissions in general. But I would like to thank you for conveying your issues and the measures you've taken to rectify them in a clear, concise manner. All too often it seems that people who live here and claim to speak the language can't get out of their own way to put their thoughts into text without filling it with Internet abbreviations, slang and spelling/grammatical mistakes. To be from Argentina and still have a firm grasp on the English language and forum ettiquette is a welcome respite. Thank you.

Thank you Jarret for your words. I like to write the way I like to read. Honestly I didn't expect such fast responses for a new member, it's great.

Perhaps higher wattage resistors are in order

I thought it also, but preferred to stay with 1/2 watt to avoid further damages.

I have a little electronic background, but your resistors blew most likely due to bad capacitors. Bad capacitors will shunt too much current through the resistors and blow the resistors. Replacing the resistors alone won't help you as they will blow again. You need to trace the path of the resistors back to where they flow. I would replace all of the capacitors with a little bit of higher ratings, higher uF and volts. The older board tend to have higher resistance.
My advice would be to replace the 5 capacitors with good brand names if possible like Nichicon. If not, find capacitors that at least have the brands on them for quality.
The 2nd option would be, to find another TCU, then replace all 5 of the capacitors, then install it. Leaking or blown capacitors are not always shown on the top, look on the bottom and some time they will leak there.

Good luck and keep us updated.

Hello bad_dude, your original post was epic for me, since it was of great help as it did actually fixed the problem, but as you suggest maybe the capacitors quality I put into is not good, I have replaced all 5 caps and 2 resistors with the values you pointed in your thread, some of them of higher voltage rating and the exact uF match.
I will give it a new try with better quality caps, and get back with the results
Thank you very much!

[Bad_dude]

Thank you Jarret for your words. I like to write the way I like to read. Honestly I didn't expect such fast responses for a new member, it's great.


I thought it also, but preferred to stay with 1/2 watt to avoid further damages.


Hello bad_dude, your original post was epic for me, since it was of great help as it did actually fixed the problem, but as you suggest maybe the capacitors quality I put into is not good, I have replaced all 5 caps and 2 resistors with the values you pointed in your thread, some of them of higher voltage rating and the exact uF match.
I will give it a new try with better quality caps, and get back with the results
Thank you very much!

I would try getting the higher uF as well. There's a limit to tolerance so don't go too high up. The higher the capacitance the bigger the capacitors and also increase heat. Heat is nothing more than unuse energy.
Another thing I just thought of is quality of soldering as well. If it's not tight and it's loose then you will have movements which can cause shortages. If the resistors burned out, they could have cause a path discontinuity and short out again once replaced. So keep that in mind.

[10thAnnivCB7]

look up the TCU fix thread here ,, its pretty cool and u can pretty much make ur own TCU and make it last long.

I put holes on my box so it can be cooled

[orangeclockwork]

I would try getting the higher uF as well. There's a limit to tolerance so don't go too high up. The higher the capacitance the bigger the capacitors and also increase heat. Heat is nothing more than unuse energy.
Another thing I just thought of is quality of soldering as well. If it's not tight and it's loose then you will have movements which can cause shortages. If the resistors burned out, they could have cause a path discontinuity and short out again once replaced. So keep that in mind.

I don't think that soldering is the problem, I have some skills in soldering as it is not the first time I do some of them.
As for the uF what would you suggest to go for? I guess C28 capacitor is the culprit, it is 220uF 35V, I will check first with Nichicon brand to see what happens, I will buy all 5 caps from that brand and reinstall.

[orangeclockwork]

look up the TCU fix thread here ,, its pretty cool and u can pretty much make ur own TCU and make it last long.

I put holes on my box so it can be cooled

Thank you, but what thread do you mean? I cant see the link.

[cloudasc]

Thank you, but what thread do you mean? I cant see the link.

The one that's in my signature that says DIY: 90-93 Tcu Fix

[orangeclockwork]

Hello everyone
Just to add a happy end to the story, I replaced the burned resistors for a couple of "real" 1/2 watt type, I say real because the ones I have put before weren't of the appropiate wattage it seems. I have been told so when I showed them to the salesman in another electronic shop I went to.
The new ones are noticeable thicker, and so far they have performed very well for a couple of weeks since, now the car drives great as it should.

Thank you very much guys, greetings from Argentina!

[illinois_erik]

Perhaps higher wattage resistors are in order

Hello everyone
Just to add a happy end to the story, I replaced the burned resistors for a couple of "real" 1/2 watt type, I say real because the ones I have put before weren't of the appropiate wattage it seems. I have been told so when I showed them to the salesman in another electronic shop I went to.
The new ones are noticeable thicker, and so far they have performed very well for a couple of weeks since, now the car drives great as it should.

Thank you very much guys, greetings from Argentina!

cool bro glad you got it sorted out

[8ball]

I used a CD5 TCU when I had a auto. the light will blink but meh it didn't mess any thing up