The Massey Ferguson MF 150 is a classic utility tractor from the 1960s–70s, featuring a simple but robust instrument cluster with a handful of essential warning lights. Most indicators are mechanical or electromechanical, reflecting the tractor's vintage design.
Massey Ferguson MF 150 Warning Light Symbols
| Symbol | Name | Color | What it means | What to do |
|---|---|---|---|---|
| Engine Oil Pressure | RED | When the engine is running, this light indicates dangerously low oil pressure, often caused by low oil level, a failed pump, or worn bearings in the MF 150's Perkins diesel. | Stop engine immediately, check oil level with dipstick, and add SAE 30 oil if needed; if light stays on, do not restart. | |
| Battery / Charging | RED | Illuminates when the generator or alternator is not charging the battery, common on MF 150 if the belt is loose or the generator has failed. | Check the drive belt tension and connections; if light persists, test charging output with a multimeter or replace generator. | |
| Coolant Temperature | RED | Indicates the engine coolant has reached an unsafe temperature, often due to a stuck thermostat, low coolant, or a clogged radiator—typical on older MF 150s working in heavy PTO applications. | Stop engine, allow to cool, check coolant level in the radiator (only when cold), and look for leaks or debris in the fins. | |
| Glow Plug / Preheat | AMBER | Lights when the preheat system is active to aid cold starting; on MF 150 it typically stays on for 10–15 seconds in cold weather. | Wait for the light to go out before cranking the starter; if it flashes or stays on, check the glow plug relay or individual plugs. | |
| Low Fuel | AMBER | Warns that the fuel level is low; the MF 150's fuel tank holds about 15 gallons, and running dry can introduce air into the fuel system. | Refill with diesel fuel immediately, and bleed the system if air is suspected (use the hand primer on the injection pump). | |
| High Beam | BLUE | Indicates the headlights are set to high beam; on the MF 150 this is controlled by a floor-mounted dimmer switch. | No action needed; use the dimmer switch to toggle between high and low beams as needed. | |
| Parking Brake | RED | Lights when the parking brake is engaged; on the MF 150 this brake is mechanical and locks the rear wheels. | Release the parking brake lever fully before driving; if light stays off when engaged, check the brake switch. | |
| PTO Engaged | AMBER | Indicates the power take-off (PTO) is engaged; on MF 150 the PTO is live (continuous running) or independent, and this light reminds the operator. | Disengage PTO before working near the shaft or when not needed; engage only at low engine speed. | |
| Differential Lock | AMBER | Shows when the differential lock is engaged on the MF 150 to provide equal traction to both rear wheels. | Disengage diff lock when turning on hard surfaces; engage only when extra traction is needed in soft ground. | |
| Work Lights | GREEN | Lights when the rear or auxiliary work lights are switched on; useful for night field operations on the MF 150. | Turn off when not needed to save battery; use switch on the dashboard. |
10 symbols shown. Icons follow ISO 2575 dashboard standards; exact graphics vary by model year.
Most Important Warning Lights
Low Oil Pressure
Common causes
- Low engine oil level
- Worn oil pump or bearings
- Clogged oil filter
What to do
For the MF 150, check oil level with the dipstick and top up with SAE 30; if light stays on, replace the oil filter and inspect the oil pressure relief valve on the block.
Engine Overheating
Common causes
- Low coolant level
- Stuck thermostat
- Clogged radiator core
What to do
Let the engine cool, then remove radiator cap (only when cool) and add 50/50 antifreeze; check thermostat operation by feeling the upper radiator hose and clean debris from the radiator fins.
Charging System Failure
Common causes
- Loose or broken alternator belt
- Failed generator/alternator
- Bad voltage regulator
What to do
On the MF 150, first tighten the alternator belt (adjusting slot on the bracket); if light persists, test the generator with a voltmeter (should read ~14V running) or replace the mechanical regulator.
Glow Plug Malfunction
Common causes
- One or more glow plugs burned out
- Faulty glow plug relay
- Corroded wiring connections
What to do
For the MF 150's diesel, test each glow plug with an ohmmeter (should read ~0.5–1 ohm), replace any open ones, and check the relay under the dash for proper clicking.
Fuel System Air
Common causes
- Running out of fuel
- Loose fuel line connections
- Dirty fuel filter
What to do
Bleed the fuel system on the MF 150 by loosening the bleed screw on the injection pump and operating the hand primer until diesel flows without bubbles; replace the filter if necessary.
Frequently Asked Questions
Why does my MF 150 oil pressure light come on at idle but goes off when revved?
This is common on older MF 150 tractors and usually indicates low idle oil pressure due to worn main bearings. Check oil level and pressure with a mechanical gauge; if below 10 psi at idle, internal wear may require a rebuild.
How long should I preheat the glow plugs on a cold MF 150?
In cold weather (below 40°F), preheat for 10–15 seconds as indicated by the glow plug light. For very cold conditions (below 20°F), you can cycle the key twice but avoid exceeding 20 seconds to prevent glow plug damage.
What does it mean if both the battery and coolant temp lights come on while running?
This could indicate a slipping alternator belt shared with the water pump on the MF 150's Perkins engine. The belt drives both the generator and water pump, so a loose belt causes both charging and cooling issues. Tighten or replace the belt immediately.
Can I drive with the PTO engaged light on?
You can drive, but avoid engaging the PTO to implements unless needed. The light reminds you that the PTO shaft is spinning, which can be dangerous if someone approaches the rear. Disengage when not in use.
My MF 150 fuel gauge doesn't work; how do I check fuel level?
The MF 150's fuel gauge is mechanical and often fails due to a broken float or corroded sender. As a workaround, use a clean stick or dip the tank through the filler neck. The tank holds about 15 gallons.
Why does the parking brake light stay on even when the brake is fully released?
The mechanical brake lever likely has a defective switch or the lever is not returning to its full off position. Check the switch adjustment under the lever; if the light remains, unplug the switch temporarily to avoid distraction.