Error Code 73 - 2012 John Deere 4720

wacummins · Apr 25, 2013

mjncad said:
Be careful taking the roof off and putting it back on that you don't damage the seal. That is a common problem that will affect your AC system's ability to pump out cold air when you need/want it. There are numerous posts on TBN and elsewhere about damaged roof seals.

Thanks for the heads up, I have seen the many posts about the seals but most were suspect before removal of the roof. Anyway mine had its seals mostly in tact, except back above the filter there was an installation error that allowed dirt to enter the cooling coils.

As for the error 73 problem
I think I may have found the cause but I have not discovered exactly where it is.....

So the other day when the machine arrived I noticed that there was a antifreeze smell in the cab and now that I have the roof off I see that there was in fact a leak ( might still be leaking ) on the left hand side of the roof. It appears to have also involved the left hand side blower/motor and possibly the front lighting wiring too. I will post some pictures of it later. I'm thinking that it was/is leaking from the heater hose in that area. This appears to have sprayed into the blower and then on to other locations.
Hopefully my cd-manual will arrive soon so I can have a wiring diagram of the roof to use in tracking this down.

I guess I should really think about how hard I want to fix this vs a warranty repair as the machine still has 6 months left on it

William.......

mjncad · Apr 25, 2013

Under warranty...let the dealer fix it, unless the dealer is too far away.

wacummins · Apr 27, 2013

Well I'm glad to say that my Error 73 adventure is over!!!!

So for a synopsis of the problem

I talked to the local dealer's technician and he looked on the Deere computer system and found another ground site to check. The suggestion was to look at the ground point under the steering wheel enclosure. He recommended that I grind the attachment site to insure good contact. Well I removed the cover and then took off the retaining nut holding the grounds down. Only problem was that Deere had changed?? the design of the mounting and used a stud welded through the cab bottom and it has a small stand off on the bottom of it. That prevents it ever touching any thing that you could grind! I did notice that the rather thin metal of the ground terminals were getting bent/smashed over the stand off so I placed a hardened washer under them to prevent that. Long story short that site was not the problem.....
So next I decided to check if this was a ground problem at all! So I took out the old jumper cables and attached one end to the neg on the battery and the other to the cab floor stud, started it up and full load ( lights and fan high) no error, remove cable and bammmmm error, reattach no error! Also I see a spark from the disconnect. Now I'm getting some progress! Its got to be the cab ground! So I removed the loader so I could get a look at it. I fight my way into the space behind the engine firewall and get a socket on the motor side of the braided lead and start to remove it.... Dam that dose not seem right, the dam thing isn't even tightened down!!! 5 seconds later the problem is SOLVED!

William......

sd455dan · Apr 27, 2013

WOW that sounds like the Main Engine to cabin ground, As an added bonus maybe your fan will run quicker and your headlights will be brighter, anyway good job:thumbsup: