Moore_rb's 66 Ebay Patrol (re)build thread

[moore_rb]

I have 2 Patrols, and 3 Multi-guages (2 later style, one early style) and two speedos (one early style, one later style)

Here's how they all looked at about 10am this past Sunday:





By Sunday afternoon, I had one later style gauge all cleaned up and reassembled to go in the Green 66 (matches up with the later style fuel sender I installed in that Patrol):




and lucky for me I had the spare - One face glass piece didn't make it I have to be extra careful with the 3 lenses I have left - I still have another gauge, and 2 speedos to reassemble




Here are a couple detail shots of the differences- From the rear (early style on left, later style on right)




on from what I saw, the early style gauge looks more robust - compare the difference in the fuel guages (later style on top, early style on bottom)

[Esteban]

We're going to keep the first picture as "Exhibit A"

Great work with the gauges, and the pictures side by side.

I have one question regarding the early style gauges, specifically the temperature one, now that you have them out. Do you see any means of calibrating it?
The reason is that in mine, once the engine is at normal operating temperature, goes to the upper mark (212°F or 100°C) while the engine itself is at 180°F.
As the engine is warming up it goes through all the range, so the sender is working properly. Thanks.

[RiverPatrol]

FYI - the later style gauge cluster used an inline regulator in the dash harness. I am not sure what it did, but it was connected to the temp gauge and (I think) the oil pressure gauge. The temp gauge won't work without this regulator.

Esteban - I have seen instrument clusters that had resistors attached in line on the wires that connect to the gauge. I always figured that was to calibrate the gauge.

[faux40]

FYI - the later style gauge cluster used an inline regulator in the dash harness. I am not sure what it did, but it was connected to the temp gauge and (I think) the oil pressure gauge. The temp gauge won't work without this regulator.

Esteban - I have seen instrument clusters that had resistors attached in line on the wires that connect to the gauge. I always figured that was to calibrate the gauge.

I'd guess that the regulator normalizes the voltage at the gauge. To continue my guess -- If the input voltage swings, the reading on the gauge should swing as well. In this case, the gauge regulator simply supplies a constant voltage for the gauge & sender to work with.

I think you're right on the inline resistor. Depending on the error type (too high/low everywhere but always the same error such as if the oil pressure gauge always reads 20psi high regardless of how much there is vs. a non-linear error such as if the gauge is correct at 140 degress, but only reads 190 when the engine is melting down on the trail from being way too hot) it shouldn't be too hard to calculate the resistor size needed to move the scale a bit.

I'd have to think about it for a bit -- but if we know the voltage the gauge can take BEFORE the needle leaves the the min reading, and the voltage it takes to reach the top of the scale we can compare that to what is sent from the sender at both extremes (min/max) and then calculate the appropriate resistor (or other circuit) to align the gauge scale closer to what the sender outputs... Hmmm. Perhaps I need to do some experiments... I like this stuff... now where did I put that schematic?


John

[miksum56]

FYI - the later style gauge cluster used an inline regulator in the dash harness. I am not sure what it did, but it was connected to the temp gauge and (I think) the oil pressure gauge. The temp gauge won't work without this regulator.

Esteban - I have seen instrument clusters that had resistors attached in line on the wires that connect to the gauge. I always figured that was to calibrate the gauge.

I'd guess that the regulator normalizes the voltage at the gauge. To continue my guess -- If the input voltage swings, the reading on the gauge should swing as well. In this case, the gauge regulator simply supplies a constant voltage for the gauge & sender to work with.

I think you're right on the inline resistor. Depending on the error type (too high/low everywhere but always the same error such as if the oil pressure gauge always reads 20psi high regardless of how much there is vs. a non-linear error such as if the gauge is correct at 140 degress, but only reads 190 when the engine is melting down on the trail from being way too hot) it shouldn't be too hard to calculate the resistor size needed to move the scale a bit.

I'd have to think about it for a bit -- but if we know the voltage the gauge can take BEFORE the needle leaves the the min reading, and the voltage it takes to reach the top of the scale we can compare that to what is sent from the sender at both extremes (min/max) and then calculate the appropriate resistor (or other circuit) to align the gauge scale closer to what the sender outputs... Hmmm. Perhaps I need to do some experiments... I like this stuff... now where did I put that schematic?


John

Mine does the same thing as Estebans.

[moore_rb]

Here's the additional info I have regarding the electrical differences in the gauges themselves-


1) The temp gauges:
The older one reads 36 ohms between the terminals
The 2 newer one read 48 ohms

This implies that there is either a unique temp sender that is correlated to each style of gauge, or that Nissan adjusted the sender's signal inline when they went to the new stye gauge (Leslie's comment above would seem to support this) -OR -- it would imply that my older style temp gauge is damaged.

2) Fuel guages:
The older style one reads 48 ohms
one of my newer ones reads 48 ohms, and the other reads 52 ohms - I think this is just a normal variance.

my old style fuel sender sweeps from 20 to 100 ohms, and my newer style sender sweeps from 10 to 90. so it seems that any fuel gauge would work with any sender, as long as you add the additional 10 ohm resistor inline if you use the newer style fuel sender (as Faux40 points out above), or if you have the regulator that Leslie mentions.

3) Oil gauge:

This is the big one- My old style oil gauge has 120 ohms of impedance (I measured 5 times to be sure) and the newer style gauges are 48 ohms. This implies that there is either a unique oil sender that goes with each, or that there is a BIG adjustment made to the oil pressure circuit in the later style gauges, or it means that my older style oil gauge is damaged.

4) Ammeter-

The ammeter is identical in both styles - but in the newer style gauge, the ammeter is attached to a steel backing plate that mounts it to the housing. If you removed the ammeter from a new gauge and unscrewed it from this backing plate, it would fit and work perfectly in an older style gauge housing, and vice- versa- the ammeter from an older gauge could be attached to the newer style backing plate, and it would work just fine in the newer style housing.


One last point about the newer style gauges --- Noting that the impedance between the later style water and fuel gauges are identical, and that they are both physically oriented so that the needles swing the same way, means that these gauges are totally interchangeable in the housing- the face plates are removable, so if your fuel gauge does not work, and you know it is the gauge that is broken, you could swap the little black face plate with a working water temp gauge and it would work just fine as a fuel gauge. Ditto the opposite- you could replace a broken water temp guage with a fuel guage just by swapping the faceplates as well.

Unfortunately, the same can not be said for the older style gauges - the faceplates are not removable, and the gauges each seem to be purpose- specific.

Great discussion - thanks all for your comments !

[IrishPatrol]

Wow I feel like I just accidently walked into the smart kids class. I'll come back when I need some tutoring.

[miksum56]

Wow I feel like I just accidently walked into the smart kids class. I'll come back when I need some tutoring.

No @#$% me too!

[moore_rb]

Mine does the same thing as Estebans.

I suspected that the water gauge in my red Patrol was also high- it would read 200 degrees when I could hold my hand on the radiator while it was running

I'll be taking this sender off the red patrol and re-using it on the green patrol, so I will take some measurements and do some calculations and will let you guys know what size 15 cent resistor from radio shack should bring it into calibration...

[Esteban]

Excellent compilation Robert. This will be a must for anyone toying around with the gauges.

One comment: I know that the sender unit is different -in operation- from the early style temp gauge to the other, and will not be interchangeable. Maybe if you have the two senders out, you cant take some readings. I will try to find a newer style that I have floating around to check it also.