Foton FT404 Voltage regulator failure

   / Foton FT404 Voltage regulator failure #1  

philtyler

New member
Joined
Nov 22, 2019
Messages
22
Location
S.W. Western Australia
Tractor
Foton 404
One day when using my 2007 Foton I noticed that the battery charge lamp failed to go out. When back in my shed I grabbed a multimeter and sure enough the battery voltage stayed at around 12V and didn’t climb up to 13.8V as I would normally expect. What to do?

The electrical circuit diagram which came with the tractor wasn’t easy to read. I soon realised that some items on the diagram were described incorrectly. According to the diagram, among other things I had two items both labelled Alternator.

I tried to work out what the terminals on the alternator were but 14 years of muck on the back of the alternator motivated me to pull the alternator off and check it out. It didn’t ‘take long to remove and I could see lots of dirt in the alternator itself, so I stripped it down and cleaned it out. Amazing how much dirt an get into an alternator over 17 years. Having not found anything wrong, once clean I reassembled it and fitted it back onto the tractor. I know knew that the four terminals were positive output to the battery, field positive, field negative and the W (Warning light?) terminal. I have to say that an alternator clean and check had been well overdue.

Nest step was to check out the voltage regulator. There was nothing that I could see that looked like a voltage regulator, but I eventually worked out it was the 5-pin plug in thingy near the fuse panel. Again the fuse panel area was very dirty and oily, so I ended up cutting out a large piece of the front bulkhead cover giving me the opportunity to give everything a thorough clean and also easy access. I later remounted the cut part of the bulkhead on a hinge.

The Foton manual states that the regulator is a JFT-125-1500W voltage adjuster. Nowhere could I find one of these including a comprehensive search on Ali Express. I did however find a 5 pin regulator in Australia being advertised as suitable for Foton tractors, a HL-1101, so I spent almost AU$60 to get one delivered to me. Although it was smaller than the existing regulator it had the correct pin pattern. I plugged in the new regulator and started the engine. Before I could get around to measuring any voltages or currents I noticed that the new regulator was smoking. Crikey!

I stopped the engine and pulled the very hot regulator out of its base. Had I done something wrong? Or was the new regulator just not up to the job? It was after all only 1/5th the size of the original. I had no idea. All I could be certain of was that I was $60 poorer and still no working voltage regulator. Fortunately it didn’t stop me using the tractor because once started there is no load on the battery.

I then set about identifying the wiring on the regulator base to see if I could fit an older style, cheap, 3-wire regulator. Something I should have done earlier. Identifying the pinout that is. Oh well! I worked out that the 5 pins on the base were 12V from the ignition switch, alternator field positive, alternator field negative, alternator W (Warning Light) terminal and 12V via the battery charge light. So a 3-wire regulator connected to the 12V from the ignition, Field +ve and Field -ve should charge the battery. I am guessing that the W terminal and the charge light terminal are somehow connected via the regulator when the ignition is on. With a 3-wire regulator, the battery charge light circuit wasn’t going to work. I would try and work that out later, once the alternator was charging the battery again.

The 3-wire regulator I decided to use was a Chinese JFT-14V-1500W unit purchased on Ali Express. At a cost of under AU$10 including postage it was certainly at the cheap end of regulators. Also here in country Australia I have found that most purchases direct from China can be in my hands in 14 days. When the new 14V regulator arrived, I connected it into the existing wiring. Here goes….. I turned on the ignition and the regulator LED illuminated. Okay, time to fire up the engine. Once the engine was running I checked that the regulator didn’t get hot and also checked the battery voltage. The battery voltage quickly rose to 13.9V and stayed there. Now that the 3-wire regulator was working I manufactured a bracket and permanently fixed the regulator.



Now to the battery charge light. I presumed that in the original regulator there would be some electronics that connected the two remaining wires together. I had no idea what but as the wires went to separate pins on the base I imagined that they weren’t just connected together. When the ignition was off there was zero volts at the battery light terminal and 8V DC at the W terminal. When the ignition was on and the engine not running. There was 12V at the battery light terminal and 9.8V DC at the W terminal. Were the two terminals connected via a resistor, a diode or something more complex? I had no idea.



For the remaining two terminals I tried various connections using diodes, relays and resistors. Eventually I decided that to design a custom circuit was frankly above my ability. I did however find a device that was used on some cars which has a W input, a battery input and a frame connection to monitor voltages and turn the battery light on and off. It would cost me about $100 so I decided against buying one. I then thought maybe I should check what other Chinese tractors do. I realised that many Chinese tractors don’t have a battery light but fit an ammeter. I then had the choice of fitting an ammeter, a voltmeter, or both. I decided to fit a digital readout voltmeter. I connected the positive wire to an ignition switch terminal so that the voltage is displayed when I turn on the tractor. My thinking was that if I can see the voltage in the system then I know that the alternator is working. This meant that the remaining original two wires were unused. This new unit again came from China at a total cost of just underAU$10. Once fitted, this worked well.



On my original regulator there were no markings to identify the terminals. The smaller HL-1101 regulator has terminals marked B, N, L, F, E. After research, although I may well be wrong, it appears that the HL-1101 requires different base wiring that what is on my tractor. Hence the smoke. So although the two regulators do have the same pin pattern, they are different and are not interchangeable.

I hope my experience helps someone else in TractorByNet land.
 
   / Foton FT404 Voltage regulator failure #2  
Whew! I had to draw that out while following along but a great post none the less. I'm sure it will help someone with a Foton charging problem.
 

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