HowTo: Replacing Fuel and Oil Gauges on a New Holland TC30

The Project:

This project took one afternoon (4 hours.) Parts cost Roughly $70. Parts & tool list at the end. Click on any photo to see an enlarged view.

I was gifted a 2007 New Holland TC30 tractor by a neighbor. It is basically sound, but many of the gauges/warning lights don't work and at some point in the past, it had a small engine fire and the portion of the wiring harness above the engine block was damaged.

After my third time running out of fuel & having to prime the injection pump, I decided it was time to fix the fuel gauge. (I can't just "stick" this tank because the fill neck has a right angle turn in it.)

The warning light for the oil doesn't work either. I want to preserve the idiot light so I can fix it up later. However, I want a gauge right now because I prefer gauges and I really shouldn't be running without knowing if I have pressure.

The goal is to end up with working fuel & oil gauges.

Safety notes:

Issues to be aware of-

• Consider disconnecting the hot side of the battery during most of this project to avoid shorts or accidentally starting the tractor.
• At one point, you'll want to start the engine while everything is partially disassembled and you're standing beside the tractor instead of in the seat. Take care not to accidentally roll over yourself while doing this. 
• Working on heavy equipment is inherently dangerous. Don't depend on my list of hazards to be complete and never be complacent.

The overview of where everything lives:

Blue arrow = Oil pressure sender. On the front of the engine block, under the radiator bracket.
Green arrow = Water temperature sender. Marked so you don't confuse it with the oil sender.
Red arrow = Fuel level sender lives under this panel.
(I'll explain the moon pies later...)

Diagnosing the fuel gauge & getting replacement parts:

A fuel gauge sender is essentially a float attached to a variable resistor (potentiometer) in the tank and  hooked up to an ohmmeter on the dashboard. That understanding makes it easy to troubleshoot, because you can check out the sender & dashboard gauge separately. If one fails, there's the answer. If both are good, start checking the wires that connect them.

The first step is diagnosing the existing sender... 

The secret hidden bolts!

The fuel level sender lives under the panel that separates the dashboard from the cowling. (The piece of sheet metal just in front of the steering wheel.) When removing that panel, note that there are a couple of bolts hidden under the top of the dashboard, so you must remove all of the dashboard bolts, and pull it up slightly to get to those two hidden bolts. You can see that this panel is bent because a previous mechanic didn't look for those bolts before applying force.

The lip that prevents pulling the panel straight up.

There's also a lip under the panel so you can't pull it straight up, but if all the bolts are removed, there's enough flex in the side panels to wiggle it free.

The fuel sender.
The connection you need to put your ohmmeter
on is under that rubber cap in the middle.

Disconnect the fuel sender from the rest of the system and hook an ohmmeter between the frame ground and the terminal in the middle of the sender while the tank is almost empty, then watch the ohmmeter while filling the tank. In my case, I got a  smooth reading of 10 -115 ohms as the tank filled. That meant the sender is working fine. Note- It's not a big deal to just pull the sender unit out of the tank, so don't hesitate to take out the 5 screws and pull it out if you'd like to do the testing on a bench instead of in your tractor shed.

The next step is to check out the meter on the dashboard. I didn't take any helpful pictures of the dashboard removal, but since you've already removed the four bolts holding it in so you could get to the fuel sender, all that's left is to remove the red throttle knob, disconnect the wiring harness, and the dashboard comes right off with a little wiggling.

After the dash panel is out, take it to your workbench and remove the Philips screws on the back to get to the gauges.

As soon as I got my fuel gauge out, the problem was obvious. It appears to have two coils, and both were visibly broken & hanging loose inside the meter. So... simple fix, right? Just order a replacement and it fits right in. ….Except that replacements aren't available, and this gauge is custom-made to fit the fancy dashboard, so a standard replacement gauge won't fit.

Plan B is to mount a standard gauge elsewhere & hook it up to the working sensor... Except there are no standard gauges made to work with a range of 10-115 ohms.  Sigh. 

Plan C then! Replace both the sender and the gauge...

I pulled the sender to measure the opening and tank depth. The opening turns out to be standard at 1-1/2 inches with 5 bolts around the perimeter. The depth of the tank is 13-1/2 inches. You *must* know the depth of your tank before you go shopping for a new sender. After a bit of research on eBay & Amazon,  I came up with this generic fuel sender/gauge set that was inexpensive and worked well.

Selecting a new oil gauge & fittings:

While shopping for the fuel gauge set, I picked out an oil gauge & sender. There are both mechanical and electric options. I went for electric because wire is easier to route than tubing. Here's the oil pressure sender & gauge I chose, which worked well.

BUT... The sender for the new gauge is a lot bigger than the old sender, because it's got a pressure-actuated lever and a potentiometer inside. The original pressure sensor is in a tight space, so I had to get an oil fitting that'll extend the oil port far enough to give me room. The other issue is that all of the generic oil gauges have 1/8 NPT threads... But this Shibaura engine uses 1/8 BSPT threads. These are close enough to force a fit, but if I'm buying fittings I might as well do it the right way. 

A few Internet searches turned up an adapter that looks like it was custom made for my problem- A T-Fitting with BSPT threads on both ends of the straight part, and an NPT thread on the side. That'll let me keep the switch sensor for the idiot light, and the gauge sensor can stick out to the side, where there's room. Expensive, but $20 is well worth the frustration this will save.

Attaching the new oil pressure sender:

Top view.
Green Arrow = Radiator Bracket
Red Arrow = Oil Pressure Sender 

There's a support bracket for the top of the radiator that attaches to the engine block right above the existing oil sender, so step one is to remove that, bearing in mind that it will have to be modified to make room when everything goes back together.

Side view of oil pressure sender.

Next, the old sensor comes out. It's 23mm, so an 11/16" wrench grips it nicely. 

Everything dry-fitted on the adapter without teflon
tape to make sure the threads are right.

Holding the assembly in place to make
sure there will be enough clearance.

When the old is sender out, dry-fit the adapter into the block & then try the two senders as well to make sure the threads are all correct and there's enough clearance. 

Adapter installed with side opening
pointed forward.

Now it all goes together. The only real challenge is figuring out which revolution to stop on so the hole on the side of the adapter faces forward and the adapter is tight enough. To do that, assemble it in this order:  1) Adapter into block. 2) Old sensor into op of adapter. 3) New sensor into side of adapter. Teflon tape goes onto all of the threads, which helps provide a little leeway on aiming the side hole forward.

New sender screwed into the side and
old sender into the top.

Once everything is screwed into place, pause here, start the engine, let it warm up & run it up to 3,000 RPM while checking for oil leaks around the adapter & senders. No use hooking everything up if you're going to have to come back & tighten up one of these connections. If there are no leaks, continue to the next steps.

Radiator bracket.

Grumble... The bracket that supports the top of the radiator won't go back on without interfering with the old sensor. 

Red arrow: Loosen this bolt bolt, pivot bracket out.
Green arrow: Drill a new 3/8" hole through both brackets here.
Blue arrow: Put a shorter bolt in the old hole.

Fortunately, if you rotate the bracket a little to the right, the engine end lands flush on the top of the power steering tank bracket. It's easy to drill a hole through both brackets, and bolt them together there. The old bolt that used to hold both brackets to the engine block will bottom out without the thickness of both brackets, so replace the original M8 1.25 X 25mm bolt with a 20mm bolt. 

Replacing the fuel sender:

The only tricky part of replacing the fuel sender is making sure the generic sender is adjusted for the size of the tank. The new sender comes with instructions for measuring the tank depth & adjusting the pieces. The tank depth for the TC30 is 13-1/2".

Old sender (on left) and new sender (on right) 

with floats in the empty position.

Senders in full position.

I followed the manufacturer's instructions, but before trimming off the excess from the float lever, also set the new & old senders side-by-side on the bench to make sure their floats ended up in the same place at each end of the range.

The hole size and bolt pattern in the top of the tank where the sender bolts in is apparently standard in most vehicles, because the generic replacement fits right in. Leave one of the five bolts a little loose so you can come back later & use it for a ground connection. Don't assume that with years of corrosion you can depend on the tank to have a good electrical connection to the frame.

Mounting the new gauges:

Here's my solution for mounting the gauges- yours will almost certainly be different, depending on what you find in your cache of resources (junk pile.)

When it came to placement for the new gauges, I ran into a dilemma- The TC30 dashboard is a plastic piece that is custom-molded. There is no room to add generic gauges easily. There's plenty of room on the piece of sheet metal below the dashboard, but that's well out of my line of sight, so not good for an oil gauge that I want to notice quickly. 

After a little thought, I decided to mount them externally in a little box above the dashboard. My first thought was to use a plastic food storage box with a snap on lid, but I worried that the plastic would deteriorate in the sun. A little prospecting in the barn for containers I'd saved to store small parts in turned up an old metal tin big enough to hold three gauges.  

Back view of gauges mounted on the tin box cover.

The metal lid was very thin & soft metal, so I risked using my wood hole-saw at low speed to cut 2" holes for the two meters. That worked fine without damaging the hole saw. I wired the gauges up with power, ground, and two sensor wires coming out, then drilled holes for the wiring to run though, and mounted the whole thing on the panel that lives right in front of the dashboard and covers the fuel tank.

Hooking up the electrical part:

The instructions provided by the manufacturer
for the new gauges.

The panel on the right side of the tractor that has the key switch on it comes off easily with about 5 bolts, so I pulled that off and did a little testing with the voltmeter to figure out which wire became hot when the key is in the "on" position.

The Red wire with the blue stripe is
hot when the key is in the "on" position.

It turns out to be the red wire with the blue stripe, so I spliced a connector in there, and attached it to the hot side of my new gauges with a bullet connector so it would be easy to disconnect if needed later on.

Red Arrow = Oil Pressure Sender
Green Arrow = Ground

Since I already had the bolt off that attached the support brackets to the block near the oil sender, it was an easy place to get a solid electrical connection to the frame, so that's where the ground wire for the both the gauges and the fuel sender got attached. Liberal use of zip ties here to keep wires away from hot areas and the fan.

Red Arrow = Sender 
Green Arrow = Ground

The other end of the ground wire that got attached to the engine block in the last picture terminates on one of the bolts holding the fuel sender into the tank, and a second ground wire goes up to the box holding the new gauges. The blue wire is the sender connection to the fuel gauge.

The moment of truth:

After hooking up all of the wires, the panel that covers the fuel tank and now holds the box with the new gauges is bolted in loosely while the engine is started to see how it all works. Not only does it work nicely, I see that the oil gauge came with its own warning light feature that gives me a red light if the pressure falls below 40PSI. I'll still probably fix the old idiot light, but that task is less urgent now that I see this cool feature. I turned the dash power back on after stopping the engine to enjoy watching the pressure fall back to zero on the new oil gauge. A most satisfactory way to spend a rainy afternoon.

Tools:

Wrenches:

• 10 mm for cowling, dashboard panel and replacement fuel sender.
• 12 mm for radiator/power steering support brackets.
• 13 mm for the panel below the dash board that the key switch is mounted on.
• 23 mm (15/16") for the old oil sender.
• 19 mm for the oil fitting adapter.
• 18 mm (11/16") for the new oil sender.

#2 Phillips Screwdriver for dashboard & old fuel tank sender.

5/16" Drill to modify the radiator support bracket.

1/4" drill for holes to mount the gauge box to the cowling.

3/8" drill for holes in the Cowling and gauge box to run wires through.

2" hole saw for gauge mounting holes

Volt/ohm meter.

Wire stripper.

Terminal crimper.

Materials: 

(Prices from 8/22, links to Amazon):

Generic fuel sender/gauge set. ($30)

Oil pressure sender/gauge. ($20)

NPT/BSPT T-adapter for the oil senders. ($20)

M8 1.25 X 20mm bolt for power steering support bracket.

M8 1.25 nut & a lock washer to re-attach the brackets using the old M8 1.25 X 25mm bolt.

Some crimp Terminals and wire ties.

An old Moon Pie tin or similar box to mount the gauges in.