1988 Jcb 3cx Alternator/Tachometer

[Sailor57]

Hi, I have recently bought a 1988 Jcb 3cx with the electric tachometer. I've already posted a reply to a previous thread on this subject but still haven't solved this, hoping someone may be able to help by uploading a photo showing the back of their alternator wiring connections. I would really like to get the tachometer working, it's either a fault with the unit itself or maybe the wiring is wrong? Thank you, Garry

[agrimax]

Hi Garry, That brown to green wire is running to earth on your alternator for some reason. The tacho would be connected to the w stud and I see nothing going to it. I'd guess the wire to earth should really be going to the w stud instead.
In your other post you say the transmission oil is milky pink. There's water in it which just might be from condensation over time but is possibly from a leak in the oil cooler.I'd assume your cooler is below the radiator. A tiny leak in the cooler would contaminate the oil but may not be particularly noticable in the radiator for some time.Would be best checked out and the oil changed. The TC would also need drained. There's a big squarish rubber grommet between the engine and bell housing that you can access the TC drain bolt through after turning the engine by hand.

[essexpete]

I would second Agrimax on the t/con oil. Most important to avoid damage.
Do the 3cxs have combined coolers/rad?

[agrimax]

At that age the cooler is more or less below the radiator but not part of it. Early models had a cooler radiator in front of the coolant radiator.

[Sailor57]

Thank you so much for your replies, I really appreciate the time you've given me. Lots to investigate. I've just finished changing the transmission oil and filters, engine oil and filter and rear axle oil yesterday and fuel filters. The transmission filler pipe/dipstick tube was completely loose and not sealed, so I thought the problem had been water running down the outside of the dipstick tube. (I've ordered the special male nut and seal from ebay for that). In the meantime I found the existing nut had been cross threaded and jambed solid. Managed to free it with a chisel, (it had been chiseled before!) It was only screwed in by about half a turn so fortunately hadn't damaged the casting threads.
I cleaned the threads on the old nut and found that the old seal was still there. Lightly greased I was then able to tighten the old nut fully and the tube is now solid. Will replace once I get the new one. I've also ordered that rubber grommet/ seal that you mention, as mine was missing. I did notice about draining some coolant from this area in my manual, but wasn't sure it applied to my machine (342628), I will need to check this as I hope it's not what you say ! Will also check the alternator wire out.

[Sailor57]

[essexpete]

That is a bit gunky! I reckon after you have run it for a few hours I might be tempted to change the oil again.

[Sailor57]

Thank you for that advise, you've confirmed what I felt was a good idea but thought I was being over the top. Must check that I'm not leaking coolant into it as advised though. No joy with changing the brown alternator lead though. Surprisingly the machine started without that lead connected and with a blip of the throttle the charging light went out and the buzzer stopped, I tried connecting to the w terminal but it sparked when 1st touching it but no tachometer movement.

[Sailor57]

Dear Agrimax, you kindly mentioned that I may have a leaking transmission oil cooler causing water in the transmission fluid, I'm a little confused about this. Is it water or oil that circulates via the small oil cooler radiator? Thanks, Garry

[agrimax]

I think your machine will have a cooler like in the picture. Engine side,below the radiator.


Water hoses go on each end and oil hoses to the small fittings.Water circulates through the outside of a matrix of tubes which are filled with transmission oil.If the matrix leaks,water gets in the oil but tbh,I'd maybe think oil could then get into the water system as well.
Do you have a cooler like above or is there a second radiator in front of the main coolant rad? If there is one in front,it'll be full of oil and is cooled by the fan and has no connection with the coolant.