Cat 143h missing gears

[Nige]

11267hr they had the motor out about 8000 hours they said they did All harnesses in rear of machine.

If the transmission control valve harness was replaced at that time then it should still be nice and soft and relatively flexible. Worth a close look anyway. If it has the appearance of being hard and with crusty insulation draw your own conclusions whether it was replaced or not.
That harness suffers a lot from heat and is usually works most of its life soaked in oil.

 

[ahart]

I went through the same thought process of the 921 wire being to blame between the splice and the solenoid, had it typed out and everything and bailed at the last minute because I decided that the only way it could affect only solenoid 7 was if the wire was broken between the solenoid and the splice which would be showing an open circuit. I’m just not sure if any situation on that side of the solenoid could trigger a current above normal code.

 

[ahart]

Part of my brain wants to say that it is possible if there’s high resistance on the 921 wire between the solenoid and the splice, that could cause a current above normal only in the solenoid 7 circuit due to it being a parallel circuit and the resistance on that particular leg only would have a relatively low effect on the total circuit resistance therefore the other solenoids would not be affected. It is also possible that this is a flawed theory, I’m open to correction.

 

[Nige]

I agree. Put simply I try to look at everything that it could possibly be and test for it before condemning the ECM, and I’ve seen enough issues with that control valve harness before to make me want to test it thoroughly before moving on.

The power for the solenoids comes from the driver circuits in the ECM so it’s always possible that one of them is fried. The thing I can’t get past is the Code change from -6 to -5 if you disconnect the solenoid which suggests the ECM is working correctly.

 

[ahart]

I agree 100%, even if I couldn’t prove beyond a reasonable doubt that the harness was bad, I’d still probably change it before I threw an ECM at it. I wouldn’t hesitate to put a known good ECM on it for testing if the option were available, but it likely isn’t or would probably have already been tried.

 

[Nige]

Bang on. If I had any doubt whatsoever I’d throw a new harness on it before replacing the ECM.

 

[Nige]

I wouldn’t hesitate to put a known good ECM on it for testing if the option were available, but it likely isn’t or would probably have already been tried.

Ah, the benefits of working with a fleet of equipment…..

 

[Mason harris]

I wish I had another ecm to try. I would have already. This is just one of them ass whoppers. So from here would y’all just throw a harness in it and see what happens.

 

[ahart]

I think that would be my move, yes.

 

[Nige]

I think that would be my move, yes.

Agreed. A harness probably costs maybe $150 vs $2000+ for an ECM. I'd go for a harness first as well.
At the end of the day if a harness fixes the problem you're a hero versus a zero if the customer spends $2k+ for an ECM that DOESN'T fix the problem.

 

[Nige]

So I was way out on my prices but not so far on the relation between them. Harness a hair under $500, a new ECM $5k. The new ECM would also need to be flashed with the appropriate software for which the dealer Service Dept would problaby charge for since it was the Parts Dept who sold it to the customer and not them.

 

[Mason harris]

Ok is there 2 separate harnesses for transmission control? There is one that runs from the ecm to the back of machine and the one that runs from that harness down to each solenoid. Im having a hard time finding part numbers for them.

 

[Mason harris]

I guess what I’m trying to ask is if I get the transmission control harness from cat is it just the little spider harness at the solenoids? Or is it the hole harness from the ecm to the back of the machine?

 

[Nige]

The transmission control valve harness, the short one with the internal splices that we were talking about above, is a 147-1771 for your machine S/N 1AL00505. That's the one that generally gives all the problems.

An easy way to get harness Part Numbers is this....
Look back at that snip I posted on the previous page. Above the 10-pin harness connector CONN 4 and slightly to the left is the letter "N", slightly to the right is the letter "F". These are the references for the two harnesses that meet at that connector. If you go to the ECM you'll find the harness plug at the other end of Line L46 from CONN 4 is also labelled "F".

Go to Grid E-1, Page 2 of the electrical schematic and you'll find a Table with wiring harness letter identifiers and Part Numbers.
Harness "F" (RH Frame - XMSN) is listed as 143-3433.
Harness "N" (XMSN) is listed as 147-1771.
Asking a dealer for the numbers above might actually get you newer numbers but when that electrical schematic was drawn up those were the correct harness Part Numbers.

 

[Nige]

I guess what I’m trying to ask is if I get the transmission control harness from cat is it just the little spider harness at the solenoids? Or is it the hole harness from the ecm to the back of the machine?

See above.
I assume that you do have access to an electrical schematic.?

 

[Mason harris]

Yes I do. Would you replace both harnesses N and F see what happen. If nothing changes replace ecm.

 

[Mason harris]

And I found the part numbers on the schematic. Thank you

 

[Nige]

I'd only replace harness N for a kickoff because that's the one with the splices in it. It's also the one that gets most of the heat and the oil contamination.
The updated Part Number for harness N is 147-1771 that was installed starting with transmission S/N 4NY00458, about 100 Serial Numbers lower than the transmission in your machine.
The difference between 137-1120 & 147-1771 is the steel "ladder rack" in the illustration. If the rack is on the transmission in your machine is still good then why not re-use that one and a few new cable ties plus a 137-1220 if it reduces the price.?

 

[Nige]

The difference between 137-1120 & 147-1771 is the steel "ladder rack" in the illustration.

Here's the breakdown of the 147-1771, just for confirmation.

 

[Mason harris]

Yes harness is ordered should be here in the morning. I will let you know what happens.