Perkins engine help

kkcomp · Sep 6, 2022

I have a JCB 1400b and none of the gauges work. I am looking to put after market ones one for cost but could use some help. It is a 4236 engine.
1. What type of tach should I use and where is the RPM pick up taken from?
2. Same with Oil pressure and temperature?
3. Any other recommendations for things to monitor besides alternator?

Delmer · Sep 6, 2022

Have you tried to diagnose the current gauges? I'd guess they're all electrical, and if none work, then it's not likely that all the gauges are broken, more likely all the gauges are disconnected.

The tachometer is almost always fed from the "W" terminal on the alternator.
The oil and temp gauges are fed from sensors, oil will be low on the block near the oil gallery, temp sender will be on the thermostat housing usually. Ground those to the block with the key on, if the gauge now works, then the sender is bad, not likely. More likely there is no power going to the gauges, in order to go to the senders, in order to turn the gauges on.

kkcomp · Sep 7, 2022

Delmer said:
Have you tried to diagnose the current gauges? I'd guess they're all electrical, and if none work, then it's not likely that all the gauges are broken, more likely all the gauges are disconnected.

The tachometer is almost always fed from the "W" terminal on the alternator.
The oil and temp gauges are fed from sensors, oil will be low on the block near the oil gallery, temp sender will be on the thermostat housing usually. Ground those to the block with the key on, if the gauge now works, then the sender is bad, not likely. More likely there is no power going to the gauges, in order to go to the senders, in order to turn the gauges on.

Thanks for the feedback but I am sure the gauges don't work because they were vandalized as in smashed with a hammer. What I need to know is are the gauges supposed to be electrical and what the voltage range would be.

hookedondiesel · Sep 9, 2022

Like Delmer said, The "W" terminal on the alt gives off an AC pulse for the tach. If your looking for a tach, find one with those spec's. The alt light on the dash "excites" the alt to start a charge on the battery. Without it, your battery won't charge. Using a voltmeter you can check battery voltage, 12.5 (usually) when not running and 14.4 (around) when running. Find where the wires go from the old senders and you should see where they hook-up. They should be all electrical.

Tinkerer · Sep 9, 2022

Sorry to read about the vandalism to your tractor. I also have been a victim of vandalism to my tractor. It infuriates me when that happens.
You have a 12 volt system.
Are you wanting aftermarket gauges that fit in the instrument panel ?
Or, a kit that has all the gauges and a mounting bracket that they mount in ? That style can be purchased in any auto parts store.
There is an alternative to your OEM tachometer called a TinyTach.
https://www.tinytach.com/diesel-tinytach
Did they smash your torque convertor temp gauge to ?

kkcomp · Sep 10, 2022

Tinkerer said:
Sorry to read about the vandalism to your tractor. I also have been a victim of vandalism to my tractor. It infuriates me when that happens.
You have a 12 volt system.
Are you wanting aftermarket gauges that fit in the instrument panel ?
Or, a kit that has all the gauges and a mounting bracket that they mount in ? That style can be purchased in any auto parts store.
There is an alternative to your OEM tachometer called a TinyTach.
https://www.tinytach.com/diesel-tinytach
Did they smash your torque convertor temp gauge to ?

Some people act like if they can't steal it then bust it up so the owner can't use it. I bought the backhoe knowing it needed work but this just adds to it. On the bright side there was 1 light the missed but I just opted to replace all of them. I am going with low cost after market and just replacing the entire plastic shroud and instrument cluster. Got a universal tach and gauge set off of EBay. Just going to monitor RPM, Alternator, Oil Pressure and engine temp. Lights came with their own switches so I will use them. Have had a hell of a time figuring out the wiring and have spent about 5 days on chasing wires one by one. Started to build a frame for the cover today so hopefully I will be back in operation next weekend or so. Thanks for the help and any suggestions are welcomed.

Tinkerer · Sep 10, 2022

Sounds good KKcomp !
If you need the service manual I have one. FREE !!
It may not be in the serial number range as yours. But they all have a lot in common.

kkcomp · Sep 19, 2022

If anyone is still following this a few more questions. Hooked a cheap Amazon Tach to the alternator W terminal not getting any readings. Also hooked a volt meter up, With engine off meter reads 12 volts, With engine running meter reads 11 to 11.5 volt. Could the two combined indicate a bad alternator?
Also hooked up a temperature sensor with gauge (yes Amazon again) but it isn't giving a reading any thoughts on why?

Delmer · Sep 19, 2022

Where did you check the volts? The big threaded terminal should have close to 14V DC when running. The W terminal should show some AC voltage. If the voltage doesn't go up on the threaded terminal when the engine is running, then check the other terminals. You'll have to look up the wiring diagram for the alternator type you have. The alternator needs excite voltage from the ignition switch to start charging, so it probably isn't getting that with what you've described so far. For testing purposes, those terminals can be hooked to the big threaded terminal, but that will drain the battery if left like that with the engine off.

I'm assuming you don't have a Lucas style, that wouldn't have a big threaded terminal, it would be all spade terminals usually.

edit: better answer, yes those two things could indicate a bad alternator. But check that the alternator is getting excite voltage, lack of excite voltage would cause those things also.

kkcomp · Sep 20, 2022

Delmer said:
Where did you check the volts? The big threaded terminal should have close to 14V DC when running. The W terminal should show some AC voltage. If the voltage doesn't go up on the threaded terminal when the engine is running, then check the other terminals. You'll have to look up the wiring diagram for the alternator type you have. The alternator needs excite voltage from the ignition switch to start charging, so it probably isn't getting that with what you've described so far. For testing purposes, those terminals can be hooked to the big threaded terminal, but that will drain the battery if left like that with the engine off.

I'm assuming you don't have a Lucas style, that wouldn't have a big threaded terminal, it would be all spade terminals usually.

edit: better answer, yes those two things could indicate a bad alternator. But check that the alternator is getting excite voltage, lack of excite voltage would cause those things also.

Well of course I have the Lucas type with spade terminals (3 on the back in a plug) The B+ terminal reads nothing and the W reads nothing. How and where do I check for excite voltage?

Delmer · Sep 20, 2022

The B+ terminal on the alternator must have battery voltage at all times, unless there is a disconnect switch for the battery. That should not go through the ignition switch. The excite voltage goes through the ignition switch to the alternator, and will be the small spade terminal, so check or make that turn on with the ignition switch. On an old diesel with a cable shut off, that is sometimes the only thing the ignition switch turns on.

Some of the Lucas alternators had two spade terminals for the B+, sometimes two spade terminals AND a threaded stud? so don't be surprised if there are more terminals than needed, some of them are connected and just extra because one spade terminal can't handle the full amperage.

Here's the simplest diagram I could find, third post from the bottom first page. don't worry about the lotus elan forum, the same alternator went into tractors as cars. https://lotuselan.net/forums/viewtopic.php?f=51&t=37766&start=

JL Sargent · Sep 20, 2022

As I recall the W terminal should be around 7 volts AC.

kkcomp · Sep 21, 2022

Thanks to all for the help. I will try to get some pictures of the alternator to post. A few things making it more of a challenge is the system was vandalized and many of the wires were cut and removed so I can't tell exactly what went where. Add to that a previous owner repainted the machine and had a philosophy of it it don't move paint it, if it moves paint it too so every wire, nut, bolt, screw etc. is the same yellow.

kkcomp · Sep 25, 2022

Here are some pictures. Every wire except W has 12volts always. W is about 0.3 AC with the engine running at any speed

Delmer · Sep 25, 2022

How about the threaded terminal on the bottom left, what's hooked to that one? or does that have continuity with B+ or the spade terminals under the connector and show 12V also even with nothing hooked to it.

Don't worry about the .3V AC on W, that should be higher, and it will be once the alternator produces electricity, like 13.5-14V.

If you don't have any wiring directions that came with the alternator, then you'll need to find a alternator model that looks similar and hope it functions similar.

kkcomp · Sep 25, 2022

Delmer said:
How about the threaded terminal on the bottom left, what's hooked to that one? or does that have continuity with B+ or the spade terminals under the connector and show 12V also even with nothing hooked to it.

Don't worry about the .3V AC on W, that should be higher, and it will be once the alternator produces electricity, like 13.5-14V.

If you don't have any wiring directions that came with the alternator, then you'll need to find a alternator model that looks similar and hope it functions similar.

That bolt is one of the ones holding the alternator together

Tinkerer · Sep 25, 2022

Is there a reason the wire bail that retains the rectangular plug isn't in the latched position ?
The plug doesn't appear to be fully seated.

kkcomp · Sep 26, 2022

Tinkerer said:
Is there a reason the wire bail that retains the rectangular plug isn't in the latched position ?
The plug doesn't appear to be fully seated.

That was just while I was taking the picture, I was going to take volt readings and said oh I need to get a picture. The terminal block has 3 wires two brown and one brown/ black. B+ and both browns go to starter to 12V, have not been able to chase the brown/ black through the wire harness and continuity checks suck when you are by yourself

So here are the readings I am getting:
B+ 12 volts always
3 plug ignition switch off both browns 12V switch on 12V I assumed these would be output wires and should have zero but that is not how the wiring is.
Brown/black 12v with switch on.

Last night I found some wire diagrams so I will use them to try and help and am posting them to maybe help someone else in the future

Vetech63 · Sep 26, 2022

I wonder if a Delco SE alternator would replace that POS. One wire out of that mess of wires and you're done.

Tinkerer · Sep 26, 2022

Vetech63 said:
I wonder if a Delco SE alternator would replace that POS. One wire out of that mess of wires and you're done.

A big amen to that, Vetech63 !
It was the best thing I ever did on my old TLB. I put the self-exciting regulator in it to.

Perkins engine help

Active Member

Senior Member

Active Member

Senior Member

Senior Member

Active Member

Senior Member

Active Member

Senior Member

Active Member

Senior Member

Senior Member

Active Member

Active Member

Senior Member

Active Member

Senior Member

Active Member

Senior Member

Senior Member