A warning light has come up on the dashboard im not sre whether its the brake fluid cylinder or supposed to represent the engine

Is the brake fluid low ? This will cause that light to come on , if it is low check brakes ! This can mean brake pads need to be replaced ,disc brakes ! Do you know where the brake master cylinder is ?

CHECK OR HAVE SOMEONE CHECK BRAKE FLUID LEVEL, BE SURE PARKING BRAKE IS NOT ON!

From Fiat LOW Brake Fluid / Parking Brake Either the exclamation mark symbol or the 'BRAKE' dashboard symbol may be used on various models of the Fiat 500. Light should illuminate until engine has started. If light remains on, it signifies the parking / hand brake is on, or that there is insufficient brake fluid in the reservoir. If light illuminates and the handbrake is not applied, braking may become defective. Seek assistance from a Fiat technician immediately.

Check to make sure your parking/hand brake is fully released, sometimes the spring that pushes back on the mechanism isn't strong enough, doesn't push back all the way, and the brake indication switch isn't engaged.
The other possibilities are that the float in the master brake cylinder is stuck (if it has one), or the level sensor has failed.

Your post gives the year of the truck as a 1993 and 1985...
The light on the dash may be your parking brake.

It sounds like the master cylinder may have failed, check for brake fluid leaks at wheels also vacuum line to the brake booster

what kind of warning light do you mean and what illuminating color is RED or AMBER is it check engine light,brake light,temperature, if is (!) then you have either worn brakes,low brake fluid due to brake ware. Check in your engine compartment the brake fluid level by the servo side and see whether the level is on Maximum if is not then surely check your brakes.

Brake warning light.

If the light is on all the time, it could mean you simply forgot to release the parking (emergency) brake. The brake warning light remains on when the brake is set as a reminder. If the brake warning light remains on when the parking brake is released, then something is amiss.
In some cases, the brake warning light may remain on if the switch on the parking brake pedal or lever is misadjusted. Nothing is wrong with the brakes and a simple adjustment should fix the problem.
If the brake warning light comes on when you apply the brakes, or is on continuously, it means that hydraulic pressure has been lost in one side of the brake system or that the fluid level in the master cylinder is dangerously low (due to a leak somewhere in the brake system). In either case, the fluid level in the master cylinder should be checked. Adding brake fluid to the master cylinder reservoir may temporarily solve the problem. But if there's a leak, the new fluid will soon be lost and the warning light will come back on.

http://autos.yahoo.com/maintain/repairqa/warning_lights/ques010_0.html

Check the brake fluid first.is it low or no brake fluid at all.is the brake fluid got dried up or leaked out. Sounds like the power brake booster is bad, that is what the master cylinder is bolted too. There is a rubber hose that has a plastic valve in it were it snaps into the booster, Pull that rubber hose out of the booster and off of the engine, Now the end that you took off the engine. You should be able to **** through the line, but not be able to blow through it. If you can then replace the valve, It is a one way valve.
If that is all right then hook hose back up to the engine and start engine, You should hear a major vacuum leak at the valve end, put you finger over the valve and it should stop making noise and engine should smooth out. If it don't the rubber hose must be leaking or the tube on the engine were the hose hooks to is stoped up. Also check the master cylinder if power booster is replaced. If the brake light is coming and going check the brake light switch. check fig for the internal assembly parts:--

To check engine vacuum, connect a vacuum gauge to the supply hose that runs from the intake manifold to the booster. A low reading (below 16 inches) may indicate a hose leak or obstruction, a blockage in the exhaust system (plugged catalytic converter, crushed pipe, bad muffler, etc.), or a problem in the engine itself (manifold vacuum leak, bad valve, head gasket, etc.).
The condition of the diaphragm inside the booster is also important. If cracked, ruptured or leaking, it won't hold vacuum and can't provide much power assist. Leaks in the master cylinder can allow brake fluid to be siphoned into the booster, accelerating the demise of the diaphragm. So if there's brake fluid inside the vacuum hose, it's a good indication the master cylinder is leaking and needs to be rebuilt or replaced. Wetness around the back of the master cylinder would be another clue to this kind of problem.
To check the vacuum booster, pump the brake pedal with the engine off until you've bled off all the vacuum from the unit. Then hold the pedal down and start the engine. You should feel the pedal depress slightly as engine vacuum enters the booster and pulls on the diaphragm. No change? Then check the vacuum hose connection and engine vacuum. If okay, the problem is in the booster and the booster needs to be replaced.
Vacuum boosters also have an external one-way check valve at the hose inlet that closes when the engine is either shut off or stalls. This traps vacuum inside the booster so it can still provide one or two power assisted stops until the engine is restarted. The valve also helps maintain vacuum when intake vacuum is low (when the engine is under load or is running at wide open throttle). You can check the valve by removing it and trying to blow through it from both sides. It should pass air from the rear but not from the front.
Replacing a vacuum booster is a fairly straight forward job. All you have to do is disconnect it from the brake pedal on the inside and unbolt the master cylinder. The pushrod that runs from the booster into the back of the master cylinder must have the specified amount of play.
You will typically find the power brake booster mounted on the firewall attached to the master cylinder. The master cylinder is connected to the brake pedal.
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I believe it's the washer fluid light

Here's a list of your dash lights and their meanings

Left
1. Door-ajar warning light
2. Oil pressure warning light
3. Check engine warning light
4. Tour or Sport for the ECS
5. Security indicator

Center Warning Lights
1st space down
Left: 4-wheel steering oil level warning light
Right: Brake warning light
2nd space down:
Left: Anti-lock brake warning light
Right: Active Exhaust Tour indicator
3rd space down
Left: cruise control indicator
Right: cruise control ON indicator
4th space down:
Left: charging system warning light
Right: High-beam indicator

Right Warning Lights
1st down: Not used
2nd down: Seatbelt warning light
3rd down: Washer fluid (2 storage containers)
4th down: Supplemental restraint system (SRS) warning light

You have one of two problems.

The most common issue it low brake fluid in the master cylinder. As the brakes wear down, the brake fluid level drops proportionally. On the side of the master cylinder is a sensor, that measures the fluid level. Open the hood and check the level. If is is anywhere close to the "MIN" line, you may have some brakes that need replaced.

The second issue, and it is more rare, is the park brake cable rusting, and hanging up.

Easy way to check either: When the light comes on, open the hood and unplug the wire going to the sensor on the side of the master cylinder. If the light goes out, your fluid level is the issue.

Thnaks for choosing FIxYa for advice!