7XXX Series Starter Problem - Again

[Duke4AZ]

I realize this is a topic that has been bantered around quite a lot, but I need some specific information and am not able to find it by searching through the thousands of posts that are out there on this site.

So I have a mid-90's model 7194 (19 hp, 4WD, diesel) made by Mitsubishi that I am having start problems with. I have done all of the usual stuff to trouble shoot it and the problem still exists. I am NOT interested in a lot of theories on what is wrong. What I am looking for is very specific information on the start circuit modification I have read about where a by-pass relay is inserted down circuit of the safety switches but ties the starter switch (key) to the start solenoid. If you don't know what I am talking about you probably don't have the information. If you do have this information, could you please email it to me at the email address on this site. Specifically, I would like the wiring diagram, any OEM or shade-tree installation instructions, and specifications on the parts, i.e. relay specs, part numbers, sources of supply, etc.

Again, this problem has been solved numerous times on this forum but I can not seem to find the detailed information I am looking for. I am not interested in starting a new diagnostic thread, just get the information I need to install the by-pass relay in the start circuit.

Thanks in advance for you help.

Duke

 

[MajMac392]

Duke, this is more info on the problem but it isn't the exact story. This may help some. I thought I had a copy of the diagram but I couldn't find it. If I find I will send it.


Electrical Starting Problem catname=Cub%20Cadet

 

[Gator6x4]

Purchase a five (5) spade terminal relay. I like the type with a tab. This allows the placement of the relay near the starter with a sheet metal screw. Some like the type that mounts through the use of a bracket. The relay needs to have the following terminals, 30-85-86-87-87a. A auto parts store can supply. Or, if you want to spend big bucks purchase one from MTD/Cub Cadet. The part # for the Cub Cadet relay is 925-1375.
Remove the wire from the key switch to the starter solenoid. (Remove the wire at the solenoid - pull from the spade terminal)If you are lucky, install this wire on terminal # 85 on the relay. If unlucky splice a wire onto the wire so it will reach where you have mounted the relay. Connect a wire to terminal # 86 and attach the other end of the wire to a good ground. Install a wire on the terminal on the starter where you previously removed the wire from the switch, attach the other end of the wire to terminal # 30 on the relay. Install a wire with a 20 amp inline fuse on the main battery wire at the starteer or another 12 volt source. Connect the other end of this new 12 volt source to terminal # 87 on the relay. No wires should be connected to terminal # 87a. Now when you turn the key to start, the voltage from the switch collapses the relay and the new 12 volt source engerizes the starter. This no start or clicking problem started when safety switches where added to the start system.

Good luck - Happy starting.

 

[Duke4AZ]

Thanks, guys. I picked up the relay at Radio Shack ($6.79) as opposed to $26.95 + shipping with CC along with a 20-amp inline fuse. Got all the parts and I probably have enough electrical knowledge to get it done from here. I would still like to find the electrical schematic if it is out there somewhere. Otherwise i will just red-line the wiring diagram I have for the tractor. Again, thanks for the information. I will post later when I have finished the implementation and let you know how it turned out.

Regards,
Duke

 

[Duke4AZ]

Remove the wire from the key switch to the starter solenoid. (Remove the wire at the solenoid - pull from the spade terminal)If you are lucky, install this wire on terminal # 85 on the relay. If unlucky splice a wire onto the wire so it will reach where you have mounted the relay. Connect a wire to terminal # 86 and attach the other end of the wire to a good ground.
Good luck - Happy starting.

Gator
Looking at the solenoid I bought and reading your description, are you certain that you have terminals 85 and 86 in the correct orientation. The reason I ask is that the relay I bought has a schematic on the package and it says "86 - on/off switch" with an arrow to blade 86 and it has "86-ground" with an arrow pointing to blade 85. I am not electrical, but I am not certain this agrees with your narrative. Am I reading something wrong or could you have reversed terminal 85 and 86? Let me know what you think.

Thanks again,
Duke

 

[MajMac392]

Duke, see attached diagram. I re-scanned it. I believe the telephone number in the right hand corner is of the TBNer that sent it to me.

 

[Gator6x4]

The wiring narative provided is identical to the information in the diagram provided by MajMac392. Learn something new everday, I was unaware Radio Shack sold relays used in an automotive application.

 

[Duke4AZ]

Once again, thanks for the information. Went to Napa first for the relay before I got Gator's original narrative on the installation so I did not know exactly what relay I was looking for. The guy at Napa recommended RadioShack. They do have some standard auto type stuff but not a lot. Looks like they had what was needed. The one difference is it does not have the 87a terminal, which I am not sure I need anyway since it does not connect to anything. I am going to wire the circuit in accordance with the diagram MajMac392 sent as it seems to be the way to go. I will repost when I have completed the exercise and let you know how it turned out. It sure looks a lot more simple than I had imagined.

Thanks again,

Duke

 

[Gator6x4]

Just my thoughts:

I would take the relay back to Radio Shack and get a relay with a 87a terminal. All relays I have installed or seen installed had a 30, 85, 86, 87 and 87a terminal. The diagram provided by MajMac392 if memory serves is the wiring diagram developed by Cub Cadet to address the no start problem. This diagram shows a relay with the 87a terminal, so it has some function. At the least I would use a VOM meter and bench test my wiring theory prior to actually installing the relay on the unit. Once the smoke starts we tend to become very excited.

 

[Duke4AZ]

The difference between the relay that CC provide and the RadioShack unit is that the RS unit is a single pole, single throw relay, SPST, and the CC unit is a Single Pole, Double Throw relay, SPDT. The SPST is either normally closed, NC, or normally open, NO. Mine is normally open, NO, meaning the relay
needs to be energized/thrown to make the electrical contact between the supply and the output. In contrast, the SPDT relay has one set of contacts in the NC state and on set in the NO state. With the SPDT you can actually route a common supply to either of two devises by throwing a single switch. Which means you can have the switch in the OFF (non-energized) position and the supply voltage is normally closed on the 87a terminal, but when you throw the switch to the ON position, the normally open contacts are closed and the voltage is switched to the 87 terminal.

For example, say you had two electric signs for a business, one OPEN and one CLOSED, assuming you could get a DC sign and it worked on a 12 VDC circuit that is. You would wire the supply to terminal 30 on the relay, the closed sign to terminal 87a which is your NC contact set and the OPEN sign to terminal 87 which is your NO contact set.. This is backwards from the way our tractor relay is set up, but bear with me on this. So, supply in on 30, CLOSED sign on 87a and OPEN sign on 87. Terminals 85 and 86 are to the relay coil as with either of the two relays in discussion here. With a 12 VDC supply voltage to terminal 30 and the relay in the non-energized state, power is going to terminal 87a, the NC terminal which is wired to the CLOSED sign and the CLOSED sign is lit. Now when you want to change to the OPEN sign, you just throw the relay and the contact switches from the NC contacts to the NO contacts, sending power to the OPEN sign.

With the SPST relay like the one I picked up at RadioShack, there is no second set of contacts and no terminal 87a. My relay is a NO relay meaning I have to throw the relay to close the contacts and thus completing the circuit to whatever I am wanting to energize. In this case the start solenoid of my tractor. In this scenario, I do not need the second contact set. Obviously, with the Cub mod, no one else does either because terminal 87a is not wired to anything. My opinion is that they had that part in their inventory list and instead of defining a SPST relay, they just decided to use the SPDT relay they already had and thus avoid the cost associated with creating, purchasing, storing and distributing a second part number. I am not certain, but the cost difference may be in part due to the SPDT configuration.

So much for the function of relays in general. I did install the relay in the tractor this evening. After consulting one of the electrical engineers where I work, of course. He pretty much substantiated what I just wrote above so I felt I was not at risk with the SPST solenoid. The installation took about 2 hours with trying to find everything and get organized. The installation was real clean. I located the relay on what could be considered the firewall just above the starter on the engine side of the firewall. One #10 screw pretty much did the job. Wired the 20Amp fuse between the battery side terminal of the start solenoid and terminal 87. Wired the key/ignition safety wire to terminal 85, terminal 86 was chassis ground, and the lead off of terminal 30 to the start solenoid relay blade terminal. After reconnecting the battery, I did a voltage check on both the load side and the coil side of the relay. I was getting 9+ VDC across the relay coil when energized (the relay is has a 6 VDC pull-in voltage) which was adequate to throw the relay. I was getting 12+ VDC across the load side of the relay which was quite adequate to start the tractor the first time and every time there after. Needless to say, this is one very happy tractor owner. It has been over a year that I have been fighting with this starter issue, just not getting around to be able to take the time to research and fix the problem. The job got done this evening and it was done successfully the 1st time. Which is not always common practice around here.

I greatly appreciate the input and advise you provided. It made the difference between getting the tractor fixed and fighting with the thing further. So, thanks again for your information, experiences and advise.
Best regards,
Duke.