Clusters, Gauges, Speedo & Odo meters

[amaurer]

So 1.1 A is flowing through the meter and bypassing the fusible link.

I think this meter DOES affect the circuit it is "testing" then.

If you think of it as a millivoltmeter (and sorry to revert to that), then I think when it's drawing 1.1A it will be lowering the voltage drop across the fusible link.

In other words, if you were to disconnect the ammeter/millivoltmeter, I think the voltage drop across the fusible link would rise by a significant percentage.

Actually no, probably not that much.

To explain why in a rigorous way would force me to write a very long post, which would expose me as the insufferable pedant that I am. Plus you probably wouldn't read the whole thing anyway.

I'll just present the math - @50A through the circuit, with a proper 0.006 ohm shunt (18"), connecting the .27ohm meter across the shunt will drop the shunt voltage by only 3%.

With a "OEM" shunt (about 3") its more like 4%.

EDIT:

Also - keep in mind that this effect is already "calibrated in" to the gauge - the markings are positioned accordingly.

 

[lostmarbles]

Heck! Here I am trying to give people the benefit of my intuition and everyone keeps responding with science.

I guess I was confused with what would happen if you tried to measure the voltage of a little watch battery with a meter that drew more than 1 amp. But these things are not really similar because a high current draw-off would stress a battery to lower the potential difference between its terminals whereas the potential difference across the fusible link is far more robust.

I promise you guys I'll start thinking more scientifically (and studying posts more fully) in the future

 

[amaurer]

I guess I was confused with what would happen if you tried to measure the voltage of a little watch battery with a meter that drew more than 1 amp. But these things are not really similar because a high current draw-off would stress a battery to lower the potential difference between its terminals whereas the potential difference across the fusible link is far more robust.

What will really bake your noodle is that the numbers above assume a perfect battery that can deliver unlimited current - the numbers above just reflect the changed distribution of power dissipation in the circuit.

If I included the discharge characteristics of the battery as well the number would be different still (but not by much - a car battery doesn't care between 50A and 51.1A). But I didn't care to do that level of calculation.

 

[bj40green]

The SPEEDO face plate

Time to finish this thread with the last item: the SPEEDO face plate.
I've tried to find as much as possible photo's of clusters for this thread and I'm sure there are more models out there but this is what I have figured out up till now.

Until the end of 1979 the Land Cruisers came with 4 different models of face plates. This depended on the markets.

From 1980 there were all kind of, mostly cosmetic, changes.
Most changes were country related.
Here is an example were there is a small 55 inserted in the miles range. Also a little decal was added at the bottom with the text [DO NOT EXCEED 55 MPH]. At this point the counter is still 5/6 digits.

From 1981 the mph range changed from: 0-20-40-60-80-100 into 0-15-25-35-45-55-65-75-85.
The counter changed into 6/7 digits. International symbols were added under the gauges. The turn indicators changed from triangle into arrow.

Note that the range now ends at 85 mph at (almost) full scale instead of 100 mph compared to clusters from before 1980.
I'm told that this is because the Cruisers came with different wheel sizes for different country's.
Also the differential changed from 4.11 into 3.73 (or the other way around). I've no idea what I'm talking about but I can use your help here. So if any of you have the correct info on wheel sizes and differential changes, please post it here.

Rudi

 

[AlexJet]

4.11 were changed to 3.73 for highway fuel efficiency. Not sure what OEM tire size was at that time.

Funny part, many of us changing 3.73 and 4.11 to 4.56 and 4.88 for off-road "efficiency" with 33, 35 or 37s.

 

[bj40green]

Here is another one. This from a 1982 BJ42 Canadian market.
Note that the range ends at 140 km/h compared to the pre 1980 which ends at 160 km/h.

Now for the tech's under us. Here are a few calibration numbers.
1978 BJ40 general market. 60kmh = 637 rpm

Unknown. 60mph = 1026 rpm

If any of you have additional info please post up.

Rudi

 

[lostmarbles]

....1978 BJ40 general market. 60kmh = 637 rpm

Unknown. 60mph = 1026 rpm

Rudi

So these are figures used to check the calibration of the speedometers Rudi? (ie. RPMs of the speedo cable that should give those readings.)

 

[BANDICOOTII]

Great Thread Rudi! Cheers on all the research and work!

 

[bj40green]

So these are figures used to check the calibration of the speedometers Rudi? (ie. RPMs of the speedo cable that should give those readings.)

Hi Tom,

My understanding is that this is the rpm's of the drive shaft with the factory differential, wheels and tire sizes.
It's also my understanding that Cruisers for Canada had bigger tires then the rest of the world, but I don't know the full story.
So the moment you change the differential and/or the wheels and tires sizes your speedo is out of calibration and I think that "Biscuit" here on Mud made it his business to supply adjusted face plates. As said before this is out of my league, but hey, I still learn every day a little at my old age. I'm sure there are some Mudders here who can give a better explanation on this subject.

Note: In theory it's possible that you buy a "Canadian" cluster to replace a "US" cluster (or the other way around). If you don't pay attention to the range of the speedo, you're in for a speeding ticket?

Rudi

 

[Biscuit]

I believe it is the RPM of the speedo cable. Some quick math for 29" tires and 4.11 diffs would put the drive shaft at ~2858rpm, which would make sense given a 1:1 ratio through the highest gear and the high range of the transfer case.

Also the calibration numbers seem consistent regardless of the speedometer scale presented. I recently put a kit together for "whats the deal" and he let me know that his BJ42 speedometer face (which is the same as the top one in post 106) is printed with 60km/h=637rpm.

 

[lostmarbles]

I believe it is the RPM of the speedo cable. .

That makes more sense to me.

I seem to recall people changing the nylon speedo drive gear(s) at the transfer case output (that drive the speedo cable) when they change diff ratios (and perhaps tyre sizes). But perhaps I'm wrong there. (I've never had to do it.)




Edit: Just did a bit of research and found that there were three GEAR SUB-ASSY, SPEEDOMETER DRIVEN (MTM) (or "speedometer drive gear assemblies" in my language) available for my 1979 BJ40 (with 15, 16 or 17 gear teeth)

 

[Curtice]

Great info. Helps me interpret FSM. For someone like me who has little to no experience in this stuff, reading FSM sometimes doesn't make sense. Very helpful.

Quick question...what is the easiest (cheapest) way to get a 12v source for testing? I don't have a nice adjustable power supply. Can I just use a 12v battery? Or can I jump to something in the vehicle?

Thanks.

 

[bj40green]

Great info. Helps me interpret FSM. For someone like me who has little to no experience in this stuff, reading FSM sometimes doesn't make sense. Very helpful.

Quick question...what is the easiest (cheapest) way to get a 12v source for testing? I don't have a nice adjustable power supply. Can I just use a 12v battery? Or can I jump to something in the vehicle?

Thanks.

The BEST way is a adjustable power supply with a current limitter.
The CHEAPEST way is a battery with a (in-line) 1Amp fuse because with a car battery, without protection, you can do some nice welding (or toast your cluster).

Rudi

 

[Pearly]

Great thread Rudi et al! Many thanks for all the input. I am just renovating my cluster, so the testing is about to start.

I've sprayed the black parts and just ordered some Letraset rub-down lettering, so will wait and see how that turns out. Now working on the silver face plate, ready for paint.

 

[bj40green]

Good luck Pearly. Please post some pics from your renovation project.

Rudi

 

[Pearly]

Still playing with it at the moment..

Temporarily rigged up the EL light to see the effect...

Still need to fine-sand and re-spray the cover, put the glass back in, redo the lettering, paint the needles....

The speedo needle had actually broken off when I bought the car - found it when I took the cluster apart! Glued it back on and waiting to paint it.

 

[bj40green]

Looking good!
Question: Why don't you remove the blue high beam indicator lens?
If you remove the rubber on the back you'll see a black stretched C clip that you can slide to one side, then the blue plastic lens comes out.

Rudi

 

[Pearly]

Is that all it is? Mine looks like it has some black glue around it, so I was thinking I would have to cut it out.

 

[bj40green]

I have no pic ready but will take one and post here tomorrow to show you how easy it is.
I have 2 clusters for sale. One 12V and one 24V, both sept. '72 till dec. '79 so I only have to lift the front to take the picture.

Rudi

 

[Pearly]

JEEZ!!! I need to get my eyes tested!!! Got home, had a look and TA-DAHHH!!! There it is!!

Thanks again Rudi! Got the little blighter off and ready for the next coat!