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Mechanical Troubleshooting

Brand: Caterpillar - Model: 7FG SERIES

Number of messages: 7

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Dave_C
Arizona, United States

I am looking for some advice/help with an intermittent code F&5 on this Cat unit. We have had several experienced electric forklift techs including our local Cat dealer attempt to repair this problem. No one can seem to get a handle on this one. Is there any one out there that my have an idea of which direction to go ? Maybe something thats not in the trouble shooting manual.

Posted 3 Jan 2005 04:26 AM

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Pick
Ohio, United States

Dave: I was essentially the creator of your
MicroCommand system, and received about 19 patents. The F5 should be reasonably easy to find. Suggest that you call me at Daewoo, 216-595-5626, or e-mail me your number at [url/email removed] AM the EXPERT

Posted 4 Feb 2005 01:49 AM

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RogerR
Arizona, United States

Dave, From past experence on the Cat truck I have found problems like yours to be a short in the drive motor field. The F & 5 is a short in D4D which also a short in the Drive Motor Field looks the same to it. If it is intermittent you may try removing the battery and washing the motor off real good. Perhaps Battery Acid is causing this. But in most instances these motors were not the best and it is a monster to remove.

Posted 4 Feb 2005 05:45 AM

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Pick
Ohio, United States

RogerR could be right, but I think if this was a motor short you would have found it long ago! Generally motor shorts result in other happenings. D4D failures are permanent, and dead short, and are pretty easy to find. I imagine this is intermittent. Suggest that you check wires 31 and 32 at power resistor, skin them back if they are rubber molded 1/4" blades, get to the crimp joint and inspect. Next go after the current sensor, P2-6 and P2-8. And if someone has stuffed a male probe into the female two pin connector, these pins will have expanded, and will make intermittent contact dependent on heat. It is definitely NOT your transistors or diodes, they are never intermittent. Driver board maybe, logic maybe, but I doubt it. If you monitor the voltage on P2-8, it should always return to approximately 6.5 volts. If it ever goes to lets say 10.5 volts, without current in the drive motor, you have an open circuit on P2-8, or a failed current sensor. Please call 216-595-5626 for further details.

Posted 4 Feb 2005 06:27 AM

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Dave_C
Arizona, United States

Thank you for all the advice on this subject.
One of the first things we did was have the drive motor rebuilt because the shunt fields were shorted. We had the battery cleaned and tested by our local battery vender while the drive motor was being rebuilt. We also replaced some worn contacts. After that we tuned the logics and returned the unit to the customer. After about 2 days the F&5 returned. We returned the unit to our shop. After Exhausted tedting and alot of labor invested we dupilcated and created a perment F&5 by disconnecting the current shunt connector. With that we tested the current sensor once again and it passed both ohms and voltage test. What we did next was replace the current sensor at $150.00. The money was well spent because the unit has been operating fine since. The suggestion by Picks to check the connector sockets for seperation makes sense. We really apprecate all the good advice. I have one more question; I was told when a F&5 occurs its caused by the negative heatsink becoming more positve than negative and the same is true for F&6 on the pump side. I don't completly understand how that works.

Posted 4 Feb 2005 12:45 AM

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Pick
Ohio, United States

The negative heatsink becoming more positive is a bunch of hogwash - can't happen! F5 & F6 (not to be confused with F"b") is checked during power up only. Drive transistors are turned on, and wire 37 is reviewed for positive voltage (motor armature is not even connected, contactors are open). If voltage is not seen, then one gets an F5. The same for the pump side, yet in this case the motor is in circuit, and wire 45 is looked at. So anything that stops the drive transistors from turning on can result in an F5. Inclusive of: Transistors blown up, driver board blown, wire 31 or 32 disconnected, power resistor R312 open circuit. POT1 dialed too low, POT3 dialed too low (these shut off the pulse within the logic, so it never gets to the transistors), current sensor failure, open wire on P2-8, or at two pin current sensor connector corresponding to P2-8. Open ciruit at logic card P2-8 connector. And last but not least, S1 cable connected to battery negative (this would be some sort of short within motor, possibly to the shunt field, or frame which is also connected to battery negative). Oh, if the negative wire of the current shunt breaks off the negative heatsink, you will also get an F5. Have fun troubleshooting!

Posted 5 Feb 2005 00:46 AM

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RogerR
Arizona, United States

Pick, Can you give your email again? Mine is desertagv@aol I work on these sometimes and you are the expert. If I run into something tough I would like to be able to get your opinion. I have your phone number just in case.

Posted 5 Feb 2005 02:21 AM

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