Perkins 4108 senders part deux

[BigAl.NZ]

Hi Guys,

I am trying to track down what senders are what on my motor which is a 1986 Perkins 4108.

Can anyone help identify whats what?

The top right hand zoomed image has two senders

1. Sender (two pin) - i have traced wires to over temp alarm

2. Sender (two pin) - comes out of the same pipe work as coolant temp alarm. The wires from this sender I have traced down the side of the engine to another sender which is in the second inset (see sender 3). So to be clear sender 2 and sender 3 seem to be wired in parallel?

3. Sender on side of engine. 3 pin but only two wires connected. As previous these wires seem to be in parallel with sender 2.

4. Two wire sender come out the top of the engine block.

Cheers

Al

[jimbunyard]

Originally Posted by BigAl.NZ

Hi Guys,

I am trying to track down what senders are what on my motor which is a 1986 Perkins 4108.

Can anyone help identify whats what?

The top right hand zoomed image has two senders

1. Sender (two pin) - i have traced wires to over temp alarm

2. Sender (two pin) - comes out of the same pipe work as coolant temp alarm. The wires from this sender I have traced down the side of the engine to another sender which is in the second inset (see sender 3). So to be clear sender 2 and sender 3 seem to be wired in parallel?

3. Sender on side of engine. 3 pin but only two wires connected. As previous these wires seem to be in parallel with sender 2.

4. Two wire sender come out the top of the engine block.

Cheers

Al

Do you have a shutdown system as well as an alarm? An electric temp gauge?

Without better pictures, using the parts manual, I'd say that 1 is the temp alarm sensor, 2 is the temp shutdown switch, 3 is the oil pressure alarm/(possibly)shutdown sensor/switch, and 4 is the temp gauge sensor.

This is just a guess, pending better information...

[BigAl.NZ]

Hi Jim

I think you are right about the temperature sender for the engine being number 4. I will get some better pictures and maybe just disconnect those wires as a isolation test.

Any thoughts on why/how 2 and 3 are in parallel?

Al
PS: are you in Louisiana?

[BigAl.NZ]

PS: If I have a two wire temperature sender, one wire presumably goes to the sender terminal of the temp gauge. Where does the other wire go?

[Lepke]

2 wire senders usually are for operating 2 gauges. The other option is one wire is an alarm, one wire to the sender. That would explain 2 senders with a connecting wire that probably goes to the alarm.
I have a 1972 4108 running a generator. The over temp and low oil pressure sensors go to the stop solenoid.

[BigAl.NZ]

Originally Posted by Lepke

2 wire senders usually are for operating 2 gauges. The other option is one wire is an alarm, one wire to the sender. That would explain 2 senders with a connecting wire that probably goes to the alarm.
I have a 1972 4108 running a generator. The over temp and low oil pressure sensors go to the stop solenoid.

I have done some googling. My two wire senders appear to have a terminal for
1. Sender
2. Isolated Earth Sender

Like here: https://www.parts4engines.com/perkin...ge-sender-12v/

I also have a 3 terminal oil alarm. Only two wires connected tho. Not sure what 3rd terminal is for.

I think the senders are as follows:

1. Coolant Alarm
2. Unknown
3. Oil Alarm (2 of 3 terminals connected)
4. Engine Temp

[SeeMonstrEd]

Doing research on my Perkins 4.236 saw your post and I think I can help with the 3 wire oil press sender. 1= oil press alarm, 2= oil press gauge sender, 3= Isolated Earth Sender. Many of the older Perkins engines came with Isolated Earth wiring for senders so the engine was not carrying current.

[waterman46]

Originally Posted by BigAl.NZ

Hi Guys,

I am trying to track down what senders are what on my motor which is a 1986 Perkins 4108.

Can anyone help identify whats what?

The top right hand zoomed image has two senders

1. Sender (two pin) - i have traced wires to over temp alarm

2. Sender (two pin) - comes out of the same pipe work as coolant temp alarm. The wires from this sender I have traced down the side of the engine to another sender which is in the second inset (see sender 3). So to be clear sender 2 and sender 3 seem to be wired in parallel?

3. Sender on side of engine. 3 pin but only two wires connected. As previous these wires seem to be in parallel with sender 2.

4. Two wire sender come out the top of the engine block.

Cheers

Al

Hard to see anything useful in the picture.
You may need to look more carefully at the wiring and draw a diagram for your future use. Number of terminals on the sender doesn't tell us much unless you can trace the wires connected to each, and tell us where they go at least within the engine compartment. Some senders rely on their threads for ground, others require a wired connection from a terminal to ground.

In general, there may be two senders low on block for the oil and two up high connected to the thermostat area.

Two senders (these are switches) will be connected in parallel - oil pressure and coolant temperature - because if either of these normally open switches get closed, there is one alarm that will sound. When you turn the ignition key but don't actually crank the starter, you should hear this alarm until she starts up and provides oil pressure. You can temporarily disconnect the oil pressure switch down low on block) and test to see if that stops the alarm.

The other two senders will be variable resistors to operate the coolant temperature and oil pressure gauges. Oil pressure sender should be very close to oil pressure switch on block and coolant sender close to top of thermostat next to coolant alarm switch.

As long as you know the engine is running fine, you can temporarily disconnect any of these wires from the senders and observe the effects on your gauges to convince yourself of the function of each.

I don't know about 1986 but on my 1982 Perkins here is no auto shutdown on these old engines, as the injection pumps are completely manual and shutdown is by pulling a kill knob connected to the pump. Unless somebody installed an aftermarket solenoid.

[Wulf]

Originally Posted by waterman46

no auto shutdown on these old engines

IMHO that is a good thing. I’m not a fan of taking control away from the operator regardless of equipment involved. I’d much sooner have an alarm blaring in my ear than have the engine shut down automatically (remember, Murphy typically strikes at the most inopporune moment). An overheat alarm tells you it’s running hotter than desired, should activate prior to the point of imminent damage. Same for low oil pressure alarm, it’s called LOW rather than NO for a reason.
Automatic shutdowns on equipment (I.e. mining, construction) typically only shut down when specific parameters have been met...for example gearshift selector in neutral or park, zero ground speed, park brake applied....implying that the equipment has safely pulled over and stopped, thus control is not being taken away from the operator.
Sorry for the thread drift.

[BigAl.NZ]

Originally Posted by waterman46

Hard to see anything useful in the picture.
You may need to look more carefully at the wiring and draw a diagram for your future use. Number of terminals on the sender doesn't tell us much unless you can trace the wires connected to each, and tell us where they go at least within the engine compartment. Some senders rely on their threads for ground, others require a wired connection from a terminal to ground.

In general, there may be two senders low on block for the oil and two up high connected to the thermostat area.

Two senders (these are switches) will be connected in parallel - oil pressure and coolant temperature - because if either of these normally open switches get closed, there is one alarm that will sound. When you turn the ignition key but don't actually crank the starter, you should hear this alarm until she starts up and provides oil pressure. You can temporarily disconnect the oil pressure switch down low on block) and test to see if that stops the alarm.

The other two senders will be variable resistors to operate the coolant temperature and oil pressure gauges. Oil pressure sender should be very close to oil pressure switch on block and coolant sender close to top of thermostat next to coolant alarm switch.

As long as you know the engine is running fine, you can temporarily disconnect any of these wires from the senders and observe the effects on your gauges to convince yourself of the function of each.

I don't know about 1986 but on my 1982 Perkins here is no auto shutdown on these old engines, as the injection pumps are completely manual and shutdown is by pulling a kill knob connected to the pump. Unless somebody installed an aftermarket solenoid.

Thanks for the reply.

I have confirmed through wire trace that:

1. 2 wire switch - coolant temp alarm
2. Still unknown
3. 3 wire switch - Oil Pressure alarm
4. 2 wire sender - Engine Temp

In respect of number 4 - I was getting readings on my gauges (one analog one digital - seperate gauges - but from same sender) that were about 10 degrees higher than was I was reading with a IR gun on the engine freeze plug.

I have now replaced sender for Engine Temp and its still 10deg higher than IR gun reading.

So I also temporarily ran two wires from sender to gauge to eliminate wiring and its still 10 deg too high.

Whats left if its not wiring, sender or gauge? A dodgy earth somewhere or the IR gun is not calibrated?

Cheers

Al

[BigAl.NZ]

Here is some better pictures.

In the photo of the top of the engine - where there is the copper pipe with one set of wires coming out the top, and one send of wires coming from another sender/switch towards the camera - that set of wires are also wired into the oil switch/sender in the second and third photos.

Cheers

Al

[waterman46]

Nice pix! Wish my motor was half that clean.

Since senders 2 and 3 are in parallel, those must be your oil pressure and water temperature alarms. Its possible the 3 wire sender contains both the oil temperature switch and the oil temperature gauge sender. Disconnect one by one and observe results.

As for IR measurement, I would not be surprised to see a few degrees difference (though 10 is kinda high) between the internal temperature of the oil or water, and an IR meter measurement on the outside of the engine - maybe also affected by the surface condition where you are measuring. I would first calibrate the IR meter by placing a piece of metal in a pot of boiling water such that just a small part of it is sticking up into air, and measure that with your IR meter. And see if different metal surfaces cause different temperature readings. I have used IR meters on electrical components and always found the readings to be somewhat flaky.

[BigAl.NZ]

Originally Posted by waterman46

Nice pix! Wish my motor was half that clean.

Since senders 2 and 3 are in parallel, those must be your oil pressure and water temperature alarms. Its possible the 3 wire sender contains both the oil temperature switch and the oil temperature gauge sender. Disconnect one by one and observe results.

That makes sense about the IR gun. I could measure the temp on the body of the sender, but there might be quite a lag?

Is the wiring as simple as this? Note the dotted line represents a temporary wire I ran between Earth on the gauge and negative terminal of the battery to confirm a good earth, but its not normally present (made no difference anyway).

Also could I put a 40 ohm resistor across the Sender and Earth on the gauge - should give a reading on the gauge of 100deg right?

Cheers

[BigAl.NZ]

Originally Posted by waterman46

Since senders 2 and 3 are in parallel, those must be your oil pressure and water temperature alarms.

Why parallel - do they share the same alarm "speaker" ?

[BigAl.NZ]

My temperature gauge is still 10 deg out from what the IR gun says.

I have replaced the 2 wire sender. So its not that.

I have two gauges in the circuit and they both read 10 deg higher than the IR - so I think the gauges are OK.

So I am thinking it must be the wiring, and I am very suspicious of the common earth wire.

I am going to measure:

1. Any voltage between disconnected earth wire from back of gauge to -ve terminal of battery. There should be close to 0?

2. Is there any point to measuring resistance between the same as above?

3. Back probe resistance between sender and earth wire with the wires in circuit. If I start the engine I assume this resistance should drop according to temperature.

What other checks can I do around the earth situation?

I know the IR temperature wont exactly match the gauge but they should be close? I am wondering about drilling out a old temp sender and threading a K type thermo couple through and measuring temp with my DMM - but not sure how to seal the hole up where I thread the wire through?

Cheers

Al