Clusters, Gauges, Speedo & Odo meters

[bj40green]

Very nice.


Post #2:

Oil lamp and charge lamp were not used on 1965 and later USA trucks, iirc.

I have no idea where these photos were taken. Can be in Japan, the Middle East or who knows.
My EPC starts in March '69 for the USA and in Sept. '73 for the EUR and GEN market and I don't have the micro fiches so it's difficult for me to trace these back to which model and market.
If any of you can reproduce the info from the micro fiches and post it here I'll add it to the Gallery.

Rudi

 

[bj40green]

That looks really fantastic, Rudy. Would you be able to make those decals out of white stickers? I would think that there would be some demand for those.

Thanks for putting all of this together.

Josh

Yes, why not? The important thing is to use a laser printer.
Printing with an ink jet can result in fuzzy pictures when the humidity goes op. Ink jet prints are not water proof. If you don't have a laser jet, print it with your ink jet printer in the highest resolution/quality mode, then take it to a good copy shop and ask for a proof print first to see if the black is everywhere the same. Some shops do a low maintenance on their machines which will not show on a regular copy but will show on a large black area.

Rudi

 

[Trollhole]

Very very nice job. Perfect job.

 

[bj40green]

Cluster and Gauges 12 and 24V set up

Let's dive into the gauges and start with the differences between the 12V and 24V clusters.
A 24 Volt cluster is the same as a 12V clusters except for:
- The OIL pressure gauge
- A resistor 30Ω 20Watt
- The PCB board
- The light bulbs of course
Here is a pic which explains the above mentioned exceptions.
I used my gauges ('73 till end '78) for this example.

The 12Volt set up:
The OIL and FUEL gauges are getting 12Volt from the ignition key.
The FUEL gauge has a build in Voltage Regulator which reduces the voltage from 12Volt to 7Volt for the FUEL and the TEMP gauge.
The AMP meter is seperatedly wired between the alternator and the battery. More about the differences in AMP gauges between this one and the later one (for '79 and later) in a later posting.

Now the 24Volt set up:
The OIL gauge gets 24Volt from the ignition key.
The FUEL gauge gets 12Volt from a dropper resistor.
The dropper resistor gets 24V from the ignition key.
The FUEL gauge has a build in Voltage Regulator which reduces the voltage from 12Volt to 7Volt for the TEMP gauge. Same story as above.
The AMP meter is seperatedly wired between the alternator and the battery. More about the differences in AMP gauges between this one and the later one (for '79 and later) in a later posting. Same story as above.

How does that look on the back of a cluster?
The arrows shows the track where the OIL and TEMP gauge both getting their 12V.



This is how a 24V cluster looks.



Here you see the gap in the track, so that the OIL gauge gets 24V and from there the resistor reduces the voltage to 12V for the FUEL gauge.



This is a 24V cluster modified for 12Volt. The resistor is removed and bridged by a piece of wire.




Of course you have to replace the OIL gauge for a 12V type (or not?). More about this in a later posting.

Rudi

 

[bj40green]

The gauges - how do they work?

How all the gauges works you can read in posting #7.
I just want to show you with a few videos what's happening inside those gauges.


(NOTE: This gauge is the FUEL gauge with the Voltage Regulator on the right side. On the top of this VR you'll see the "breaker")

A heating element is wrapped around a bi-metal. The heat is determent by the resistance of the sender. If the resistance is high, the current is low, so the heat is low, so the needle is in the left position. When the oil pressure goes up or the fuel is full or the temp is high the resistance of those senders are low, the current is high, so the needle goes to the right position. Because of the heat the bi-metal will bend and move the needle. As simple as that.
Here is a video of the TEMP gauge. Especially for you folks I drilled the tiny rivets off and removed the face plate (which I dropped while recording the video - sorry).
Watch the blackish vertical arm bend at the bottom that moves the needle.
As per the FSM the gauge is connected in series with a 3.4 watt light bulb (in my case a 3W because I don't have a 3.4W light bulb).
Here is another one from an OIL pressure gauge for a BJ40 24 volt.
For the tech guys: The markings on the OIL gauge represents: 0 28.4 56.8 and 85.2 psi or 0 2 4 6 kg/cm²

The AMP meter is a different story. There are 2 models.
The pre '79 model and the '79 and later model.
See posting #9 bottom pictures.
The pre '79 model is an INTERNAL shunt type and is a magneto meter. The '79 and later is an EXTERNAL shunt type. Actually it's a mV (milli Volt) meter.
At the first the full current (except the starter current and for diesels the glow current) will flow through the AMP gauge.
At the later model the current stays under the hood and the gauge reads the voltage drop over the Fusible Links.
For a full explanation on the pre '79 model go back to posting #7.

Rudi

 

[73tlcv8]

I wired a simple 7v 3 terminal voltage regualtor in place of the bi-metalic regulator in the fuel gauge. I never could keep the thing working reliably, it would stick and peg the fuel and temp gauges. No problem with the solid state version for over a year.

 

[bj40green]

The Voltage Regulator

So the FUEL and TEMP gauge work on 7 Volt but where is that coming from?
In the picture below you'll see the VR on the left.
A wire wound resistor is wrapped around a bi-metal switch (It's the same principle as for the gauge needles).
The resistor heats up, the bi-metal strip bends and the switch opens. The current flow stops, the bi-metal strip cools down and the switch is closed and this process repeats itself. Now here is the kicker..... heating up/opening and cooling down/closing takes each ± 1 second or so. So one second 12 Volt, one second 0 Volt means an average of 6 Volts or when the engine is running 50% of 14 Volts is 7 Volts.
This 7Volts is the value the FSM (posting #7 pages 12-27 and 12-28) is speaking of and also says:
[QUOTE:] -Caution- Do not check the 7V terminal at 12V or 24V. [END QUOTE] because you'll measure only an intermittent 0 and 12Volt.
This "switching" behaviour is also responsible for the "flashing" of the light bulb when you test the FUEL or TEMP gauge with a test light as per the FSM (see posting #7 page 12-26 of the FSM).

If you look at the pic in the previous post you can see an adjustment screw on the rights side of the "breaker" points. Here you can adjust the interval time for the VR. The problem is that you can do this only when you have it all apart and in a test situation on your work bench. I don't see the need to change this setting unless your gauges are really off spec. BTW the screw is sealed/fixed with a greenisch ....... I call it "nail polish" but if somebody knows the right word, please tell me.

Rudi

 

[bj40green]

The OIL gauge and sender / 12 and 24Volt

As mentioned before in this thread, there are 2 models of OIL gauges and senders. The 12Volt and the 24Volt model (for BJ's only). The difference is the internal resistance for each model.
44Ω for the 12V model and 66Ω for the 24V model.
Of course the senders are different too.
Here is how it works. As we've seen before, the FUEL and TEMP gauges are fed 7Volt by the internal Voltage Regulator from the FUEL gauge.
The OIL gauge works on the same 7Volt principle but now the Voltage Regulator is inside the OIL sender.
The (pressure) membrane is moving the working point from the VR to a higher level.
If there is no pressure the VR is open, the gauge shows Low (= 0 kg/cm² or 0 psi).
If the pressure is low the VR will open after a short time of heating up the bi-metal and the gauge will show at the second mark (= 2kg/cm² or 28.4 psi).
If the pressure is high, the membrane moves the VR (and so the bi-metal) to a higher working point which will result in a longer time (heating up) before the VR opens up. The gauge will show at the third mark (= 4 kg/cm² or 56.8 psi)
The fourth (H) mark = 6 kg/cm² or 85.2 psi.
As you can see in the FSM test procedure (posting #7) the gauge is tested by grounding through a 3.4 Watt light bulb. There is no mentioning of "flashing".
The sender is tested by applying 12Volt to a light bulb which is connected to the sender. The test shows the light bulb "off" when the engine is not running and "flashing" when the engine is running.

Rudi

 

[Tanker120]

Thanks for taking time to post this information, this is great stuff and will be a great resource!

 

[lostmarbles]

This thread is almost enough to tempt me into getting out my spare combination meter to see if I can get a bulb to blink too.

Actually I'm surprised my gauges have all worked so flawlessly for over 30 years (excluding my stubborn/lazy ammeter of course) ... considering how dodgy their technology appears to be.

Thanks for all your efforts here Rudi

 

[Hugh Heifer]

Thanks for all your efforts here Rudi

Ditto. Good tech.

Now we need a thread on after market gauges and usable electrical or mechanical sending units.

 

[John McVicker]

Rudi,

Suscribed.

This is a great thread & we really appreciate your work.

I am biased as I am currently trying to repair my non working fuel/temp gage. Have gone back to this thread several times. Hopefully I will finish up tomorrow.

Thanks for your efforts.

John

 

[bj40green]

Thanks guys for all the kind words.

[John wrote:] Have gone back to this thread several times.
Aha! That's why the counter is going up so fast. Just kidding!

@John: If you need any help let me know and I'll talk you through it.
These gauges are pretty indestructible. I just finished my second spare cluster (24V but easy to convert for 12V) with an almost toasted FUEL gauge. The back side of the face plate was black with sooth but it didn't burn down. Amazing.
Here are some pics:

The one on the right is the 24V model with the dropping resistor in the right bottom corner.

For testing I use an adjustable power supply with an adjustable current limiter. I set the current limit at 300mA for testing the VR. The VR pulls 200mA intermittent after a 3 second warm up. When testing the gauge with the test light bulb I set the limit at 500mA. The VR and the gauge together are pulling some 400mA when everything is working correctly, so you see the amp meter swinging between 200 and 400mA.

Rudi

 

[John McVicker]

Thanks guys for all the kind words.

[John wrote:] Have gone back to this thread several times.
Aha! That's why the counter is going up so fast. Just kidding!

@John: If you need any help let me know and I'll talk you through it.
These gauges are pretty indestructible. I just finished my second spare cluster (24V but easy to convert for 12V) with an almost toasted FUEL gauge. The back side of the face plate was black with sooth but it didn't burn down. Amazing.
Here are some pics:
View attachment 591385

The one on the right is the 24V model with the dropping resistor in the right bottom corner.
View attachment 591386

For testing I use an adjustable power supply with an adjustable current limiter. I set the current limit at 300mA for testing the VR. The VR pulls 200mA intermittent after a 3 second warm up. When testing the gauge with the test light bulb I set the limit at 500mA. The VR and the gauge together are pulling some 400mA when everything is working correctly, so you see the amp meter swinging between 200 and 400mA.

View attachment 591387

Rudi

Rudi,

Thanks for the offer of assistance w/my fuel gage. Today, I was unable to resolve my issue so your knowledge would be helpful.

I don't want to mess up your thread, so would you prefer a PM to discuss, or do you want to do it in this thread. I will wait for your reply. This is for my 2/'75 40.

Thanks, John

 

[bj40green]

Hi John, let's start here. I think other people can learn from what we're doing. If necessary we can always side step to PM or EM.
So tell me what the problem is and what you've done so far.

Rudi

 

[John McVicker]

Hi John, let's start here. I think other people can learn from what we're doing. If necessary we can always side step to PM or EM.
So tell me what the problem is and what you've done so far.

Will do. Don't know what time it is where you are but it will be about 2 hrs. before I can post a pic. Until then I will try to describe my problem.


Am trying to repair the broken wire on my 2/'75 40 fuel gage, going from the upper middle post over to the VR. This may/may not be my entire problem...but I know this must be fixed b/4 going any further.


Don't know if this wire also acts a a fuseable link, but it seems to NOT take solder, for a quick/easy repair. It appears that the end attached to the VR is welded and not soldered. The other end, I think, is brazed, not soldered.

If all this is accurate can you suggest a repair method ? (if a resistor, what size ?) I may have blown this wire while trying to determine my problem over the last several days. So this may not get my fuel gage working again, but like I said, this must be fixed b/4 going further. This gage has been discontinued for my year.

Thanks and let me know if you want me to post that pic I mentioned.

John

 

[bj40green]

Hi John, If you mean the twisted wire with the arrow in this pic

then we're talking about the same wire. This is a PO job.
It's the VR output to the TEMP gauge. It's just plain copper wire. Any wire will do. I had to replace that one myself. I used a piece of telephone installation wire.

Don't know about your soldering skills but here is some advice:
* Use a small (40 - 80 Watt) soldering iron.
* Use rosin core solder wire.
* Prepare your wire by adding some solder on both ends.
* Prepare both terminals by applying a bit of fresh solder.
* Solder the wire in place.
* Don't solder to long, the plastic will melt.
* Just let it cool down by air. Don't apply a moist cloth or water to cool it. The solder will crack by cooling down too fast.

Good luck and maybe you can post pics before and after.

Rudi

 

[John McVicker]

Thanks Rudi,

Yep, that is the wire. Will attempt soldering tomorrow. Thanks for the tips.

My broken wire being for the temp gage...would of course be the reason my temp gage doesn't work. But would that same broken wire explain why the fuel gage doesn't work ?

Thanks, John

Edit: By the way, I saw that pic in one of your post. So, the PO just twisted some wire around the original wire & then soldered/joined it ?

 

[bj40green]

Thanks Rudi,

Yep, that is the wire. Will attempt soldering tomorrow. Thanks for the tips.

My broken wire being for the temp gage...would of course be the reason my temp gage doesn't work. But would that same broken wire explain why the fuel gage doesn't work ?

Thanks, John

Edit: By the way, I saw that pic in one of your post. So, the PO just twisted some wire around the original wire & then soldered/joined it ?

Yes that broken wire is the "power" for the TEMP gauge.

The twisted wire: It looked like that. I took it out and replaced it. As you can see the left stud was broken and the one on the VR side was also very weak. I glued it back in place with 2 component glue.

Do you have a multi meter? So we can do some meassuring.

Rudi

 

[John McVicker]

Yes, I have a meter, so we can do some testing. Is this to determine if my fuel gage has other problems ?

And my face plate of the gage is still attached, so I will be attempting this repair w/o removing it.

Thanks, John