Autogauge Stepper Motor Series and Smoked Series Gauge Install and Review

From left to right: Oil temp, Oil pressure, Water temp.

The Oil temp gauge is an Autogauge Stepper Motor Series and the other two are Autogauge Smoked Series.

The Stepper Motor Series does the whole Defi start up ceremony where the needle does the full sweep and the lights flash upon start up. It also makes a loud, prolonged beep noise upon start up which can be a bit annoying. The Smoked Series are silent on start up.

Prior to fitting

The Stepper Motor Series oil temp gauge has a small white (2mm or 2.5mm allen) calibration screw at the back of the gauge. So before I installed the gauge to the car I checked the calibration by hooking it up to a spare car battery I have and placing the sensor in a pot of water. I boiled the water and adjusted the screw so that the gauge would read 100 degrees Celsius to ensure accuracy.

The Smoked Series do not have calibration screws, at least not exposed in its case - I have not opened them up to inspect internally.

The Install

First, I checked the combined current draw of all three gauges with a multimeter and found that it is around 0.3 - 0.4 amps. This was surprising as I was worried I'd have to split the wiring for the three gauges to spread the current draw to prevent exceeding the amperage rating of the 180sx's interior electrical circuits (eg cig lighter, audio unit, etc). I can't guarantee that this is the case for all after market gauges so check the current draw of your particular gauge!

With this knowledge, I tapped into the wires of the audio unit power supply: Permanent 12V (battery+ive), Accessory, and Illumination. And earthed it to the body. 

Automotive 8Pin connectors are your friend here:

Illustration from the Narva Website

What you have is three gauges, meaning three earth wires, three +ive, three sender wires etc etc.

You need to combine each category into one pin. Each pin of the Narva connector is rated at 20amps so its more than enough to handle the current draw of these gauges.

Note: the stepper motor series has a permanent 12V+ wire for peak recall memory so you'll need add that, if you are just installing the smoked series then the above diagram can be followed 100%.

This is the neatest way to install these gauges. Hard wiring them by soldering the wires into your existing electrical circuits means you need to cut the gauge out if you wanted replace them or remove them for whatever reason. Using connectors means you can replace each gauge (if one of them fucks out) efficiently and neatly - just like factory.

Senders

Im running a JAB design coolant neck sandwich plate (which is exactly the same as the Gktech coolant neck sandwich plate [I believe is a "JAB" design originally]) for the water temp sender and a Shadow Pro oil filter sandwich plate for the oil temp and pressure senders. Best thing for pressure senders is to isolate them from vibration - that means installing it OFF the engine (ie on the body somewhere) and use a braided oil line coming off the sandwich plate and onto the sender. This will prolong the life of your sender unit. 

Use thread sealant (I used Permatex thread sealant and it seems to work quite well) for all the sender threads.

Sandwich plate between head and coolant neck. (Easier to view if you download the image and zoom in)

Pressure sender mounted remotely. I still need to get a braided line 1/8NPT male and female fittings.

Completed Install:

Leaking Water Pump

SR20 water pumps are not too bad of a job to do. Easily do-able at home with basic tools. 

A quick run down:

1. Drain coolant
2. Remove top hose (to allow shroud to be removed)
3. Remove radiator fan shroud (from the top)
4. Back off the clutch fan bolts (x4) but do not remove them
5. Back off the alternator/waterpump belt
6. Remove clutch fan and pulley
   [Steps 4-6 is done in this order so that you can undo the 4 clutch fan bolts while the pulley is held stationary by the belt/engine]
7. Unbolt the water pump, give it a gentle tap with a rubber mallet or pry with screwdriver making sure not to score the mounting surfaces of the water pump. There will be a lot of coolant in there that comes rushing out so using a big tray underneath while you do this is a good idea.
8. Remove as much coolant from block as you can, just soak it all up with rags.
9. Raise the front of the car a bit more so that no coolant can seep out and interfere with the setting of the sealant
10. Clean the mounting surfaces well, remove all old sealant with a razor, use some scotch brite and brake cleaner/grease wax remover. How well the new sealant sets and the longevity of the seal itself is dependant on how clean these surfaces are, this is not an area to skimp on.
11. Transfer the studs of the old water pump to the new water pump
12. Apply sealant to the mounting surfaces of the water pump and tighten bolts to torque specs. (IIRC I just did it with a 3/8 ratchet by feel, didn't have a torque wrench at the time but it is a good idea to do this and also do the bolts in sequence - from the inside to the outside). I used Permatex Ultra Grey and followed their directions, which was to mount the water pump finger tight and let it set for a while before applying full torque to the water pump bolts.
13. Let the sealant fully set (time depends on sealant) before putting coolant back in.
14. Remember to re-install the drain plug on the radiator.
15. Refit water pump pulley and fan.
16. Refit all belts
17. Refit radiator shroud
18. Refit top hose
19. Undo the top radiator brackets and remove them
20. Slip a large cut out of cardboard (or similar) to block air flow to the radiator while bleeding the cooling system (so that it can reach normal operating temperature thus opening the thermostat and cycling the cooling through for air bleed purposes)
21. Fill coolant up to the top of radiator and run the engine
22. No need to turn the heater on as there is always coolant running through the heater core on S chassis vehicles - don't run the fan as you'll be cooling the coolant
23. Once the lower hose gets hot that means the thermostat has opened and coolant is circulating
24. Undo the bleed bolt at the top hose to head junction until coolant comes out and reinstall
25. Fill the radiator to the brim and close the cap
26. Remember to remove the airflow blocking cardboard and reinstall the top radiator brackets
27. Fill coolant reservior about 1cm above max
28. Check for leaks

Trick here is to make sure the area is bone try and drop the rear end of the vehicle down or raise the front up so no coolant situates itself on the sealant while it sets. There is one little bleed screw on the top hose to the head junction for when you put the coolant in. I use Nissan genuine and wouldn't use anything else, its not expensive, and easy to get.. so why get anything else that may shorten the life of your water pump or offer compromised corrosion protection of your cooling system.

Take note, not all SR water pumps are the same. S13 black/red top run different water pumps to S14/S15!