Automatic Transaxle Interlock Electrical Problem

[chemman]

I have a 2005 Craftsman DYT 4000, Model Number 917.275642, lawn tractor with a B&S 18.5 I checked the seat interlock and the brake/clutch interlock switches and both are operating normally. I checked them out using a DVM on ohms setting and there was no indication of high resistance or dirty contacts. It does not matter if the ignition switch is in the run or reverse operation location. I also ohmed out the ignition switch and it is fine. HP engine (Model 31P777, Type 0348-E1, Code 0411037E, Date Code 08082400) that has developed a strange problem related to whether or not the automatic transaxle is in neutral or engaged. When I pull the transaxle disconnect rod out and "lock" the transaxle in neutral so I can easily push the lawn tractor around, the lawn tractor starts, runs, the blade engages with the electric PTO, etc. even when I let the brake/clutch pedal up just like it is supposed to.

However, when the transaxle disconnect rod is pushed back in, that is when the fun begins. The lawn tractor starts normally. However, just as soon as I release the brake/clutch pedal, the tractor begins to move and dies. If I press the brake/clutch pedal down fast enough, the engine recovers and runs great.

I looked at the electrical schematic for the lawn tractor and I do not see an interlock switch for the transaxle.

After I mowed 2 weeks ago, I changed the oil and I "locked" the transaxle in neutral so I could move the mower around to take advantage of my driveway's slope when draining the oil and then in removing the oil filter. After I finished, I took the transaxle out of neutral and all worked well, and I put the lawn tractor away in the shed until I again mowed last week with zero problems. Today, I got the lawn tractor out, parked it in front of my garage for my pre-mowing check, and when I went to start it, it started up, but when I let up on the clutch/brake pedal, the tractor died. If I put the transaxle in neutral by pulling out the disconnect rod, all is well except for motion.

So, is there a hidden switch I'm missing? As a thought is the Reverse Operation Switch somehow involved?

Any help would be appreciated.

Thanks

 

[eljefino]

Your switches can ohm okay but not pass much current.

How do they work, do they ground the coil to cut spark or are the on the positive side of things?

 

[chemman]

The switches are on the positive side of things. The interlock switches I can find are working OK. I am looking for a "hidden switch" tied into the transaxle manual disconnect rod that the manufacturer left out of the owners manual. The interlock switches are relatively low current switches that I double checked with an analog VOM to see if they were flakey. There was no wavering of the needle.

I appreciate your response, as I have seen that before myself.

Thanks again!

 

[chemman]

Problem fixed.

Just to update this thread, I finally tracked the problem down to a faulty Reverse Operation Switch (internal contacts were not making a good electrical connection) AND corroded wire to crimp connection on all the Packard Type 56 male and female connectors in that circuit. I replaced the 2 male and the 2 female crimp connectors with new Packard Type 56 connectors that were both crimped and soldered.

 

[JTK]

^ Good find!

I was going go suggest looking into goofy stuff like the seat switch. Glad you got it.

 

[chemman]

Thanks. I'm glad I still have an old style analog Volt-Ohm-Multimeter (VOM) with a large meter face as it makes tracking down intermittent connections a little easier. By using it and and thumping the various connectors with small tool, my sanity was saved!