HJ61 Electrical saga

[cross_country]

Hi,

I've got an 87 HJ61 with a 24V system. A year ago I left the lights on, draining both batteries. About a month later I left it sitting in a field for 7 months while I was away. Upon my return the batteries were dead.

I got a boost and went to the shop and bought one new battery, and got a used battery from a friend. While I was driving to the shop the volt-meter in the dash was bouncing from 16 to 32 with the engine RPMs.

With the new/used battery combo I was sweet for about 2500km. During this 2500 km I noticed a bit of belt squeak.

Then the Filter/Battery/Turbo lights all came on and off intermittently for a few days. Then the batteries went flat.

The alternator belt was super loose so I replaced it, but still the light show and dead batteries.

I bought a second new battery and charged both of them up. Still have the light show on the dash. When I put on the brights on and the fan on high the alternat puts out 15amps. I haven't had dead batteries since I put the two new ones in.

I put in a new voltage regulator, but I still have the light show on the dash. volts are slightly above 24 at idle, and get up to 28 with rpms.

I suppose it's time to pull the alternator and bring it in. Anyone have any other ideas?

[goldchaser]

I'd check your fusible links off your batteries first,they can look ok but be buggered.Start there first before blowing money on alternators etc.
cheers goldchaser

[Fantom]

I had similar issues with mine but it is 12Volt. I would occasionally have the light show and the batteries would not hold a charge but the alternator was outputting 14-14.6 volts. I first replaced all the ground cables with 2/0 welding cable, the problem went away for a bit, then I bought an aftermarket voltage regulator and noticed some corrosion on a couple of power cables, replaced the stuff and it has been fine for the longest time. I had the lights freak out on me recently and it turns out to be a short in the rear harness where water damaged the wires and the stop, turn and back-up lights were shorting and causing more chaos. Now it's all fixed. See how all your grounds look, engine, body, battery, etc. check to see if you have any shorts, corroded cables, voltage leaks. Troubleshooting electrical is a PIA. Good luck.

[Ron R]

Cross_country,

Do like Fantom suggested. Look for all the groundings you can find related to engine-body-chassis-batteries-alternator.
Do not forget the interconnection of the batteries. Clean all poles and clamps and make sure the clamps fit snug.

[Frode S]

In 24v systems, it is vitally important that you change bouth batteries at the same time, and that the new batteries are identical (age, specks and brand). If they are not, one of them will be overcharged and boil, the other will get no power at all...

Remember that the alt. sees the two batteries as one 24 volt battery. If the internal resistance is different in the two, of if you tak out ANY 12 volt from either battery, bouth will die... I know this from experience...

[Ron R]

Yeh, Frode S,
I second that.
Manufacturer even advises to use two batteries from same batch if possible.
And never, NEVER, NEVER draw 12 V from one of the two, not for an alarm, not for the memory of a radio, not to jumpstart a 12V rig....NNNEEEVVEEEERRRRR.

If this happens for one reason or another, disconnect both batteries, switch them to parallel (minuspole to minuspole and plus to plus) and charge them with one (electronic regulated) charger untill charging stops.

[cross_country]

I had checked all the battery connections and the ground from frame to engine and battery to frame and all were tight and had low impedance.

Both batteries are (now) the same model and started from a full charge.

I went for a 800km drive this weekend and was constantly entertained by the electrical system! volts at 24, 28, 32 (and higher!), dash lights on and off etc and eventually something must have popped because the volts settled at 24.

I pulled the alternator and left it at the shop and they say the bridge rectifier is blown. Whether this is the cause of all my problems or just a symptom of another problem I don't know yet.

Soooo, Alternator is a Nippon Denso ND 24V 40A 100213-0520 and a new one is $650 NZD. I haven't had any joy yet finding a used one at the wreckers here in New Zealand so I am expanding my search to the world.

Has anyone ever got a new rectifier or am I looking at replacing the alternator with a different model and getting a seperate vacuum pump?

I haven't seen the bridge rectifier yet but if the whole thing needs to be replaced it must be an IC and not 6 seperate diodes. Maybe I can get 6x 15A diodes and build a new one?

[Ron R]

Are you sure one (or more) of the diodes are gone? From your description it sounds more like an intermittant contact.
If you can, just replace the rectifier. Or try to find comparable diodes and replace the old ones.
Maybe 15A is a bit tight. 20A will be better (if they fit and you can get them)

[cross_country]

Yep there are definitely a couple of diodes that are totally blown. They are the round button type ones where there is only one lead as the package is the other lead which is soldered directly to a metal surface.

The shop says they can't solder new ones in because they always get the diodes to hot and fry them, so I am looking for someone who is a bit more confident in their soldering skills. Surely someone must be able to solder in a diode without melting it.

[Ron R]

Trick is to use a 'massive' and hot soldering iron. 200-300Watts. 450 if available
Prepare the surfaces well and use a good quality raisin core.
Press the diodes in the plate and then with a short, quick touch of the iron solder the lead and cool with compressed air or a cooling spray. Best is to do it one by one, cooling inbetween
How do the think the manufacturer would do this?

[cross_country]

Is a butane soldering iron got enough grunt?

Thanks for your ideas! Here's a picture of the beast. the top 1/2 ring is the negative side and the bottom is the positive bus.

It looks like the two diodes on the right of the negative bus have been replaced already. The connection on one of them is poor and the left most diode was blown and has been removed.

Why are there four diodes on each side though?

[Ron R]

Looks a bit messy in there!!
Propane heated soldering iron is fine, as long as the flame doesn't get near the spot you have to solder.

If you just have a torch, heat a piece of iron (well cleaned -sanded or filed) and use that as soldering iron. Heat it, take the flame away and check or it is hot enough to melt a soldering wire instantly. Then quickly do the job and cooool the diode.
Be carefull with that hot piece of iron!!!! Don't burn yourself.