I lost the instructions to my voltage tester. Does the red probe goes on the ground and the black on the black wire to test for voltage?

have you checked voltage and ground for blower motor? At the blower motor, red wire is voltage, black wire is ground. You can take two wire connector loose from blower motor, use both ends of testlight on connector wire terminals, Key on--hvac controls on--hi speed. If the lamp comes on, you have voltage and ground good enough for test lamp. If you have good voltage and ground for blower motor and the motor doesn't run, suspect the blower motor. If the lamp doesn't come on, your missing either voltage or ground? In stead of using wire connector ground, you could use chassis ground, clean metal spot, probe red wire, If lite doesn't come on, your missing voltage and you'll have to backtrack circuit. See the top right fuse, 40 amp fuse, that fuse is only for hi speed. Not only check the fuse, use a test light check fuse for voltage, hot all the time. If you follow that wire down, in diagram, you see it goes to switch side of relay, left side in diagram. When that relay is energized that short line moves to other terminal carries voltage for hi speed. The control side of relay, right side in diagram, needs voltage and ground in order to energize. If it doesn't energize, no voltage hi speed. Orange wire is voltage for control side, black wire is ground. I can only help with testing, good luck.

normaly red is alive and black is the neutral

Hi, 1.connect the trailer connector to the vehicle connector. 2. Make sure your tester is on DC volt selection. 3. Take black test probe (usually negative) to the frame of you trailer. (You want to have a good contact with metal so you'll be able to get a good negative polarity; no rust or paint between the test probe and the metal.) 4. Turn on lights and check the DC volt between the metal frame of your trailor (black probe) and the wires which goes to the lights (red probe).
...if you got voltage (12V or 24V depending of your system voltage) it means that the bulb is gone. (you should have 12V or 24V only on one (1) wire). If you do not have any voltage on one or other wires it probably means that you got cut wires... It might be the case if it was working before.
If its a new installation make sure that voltage is coming out of the plug. (you do the same test but you place the negative probe on metal from vehicle and the red probe into the pins of the connector.)
*** In a DC system we usually get Red as Positive (+) and Black for Negative(-) ***
hope it will help

best regards

K4221C photo cell page at Intermatic:
http://www.intermatic.com/products/photo%20controls/commercial%20%20industrial/stem%20%20swivel%20mount%20-%20thermal%20type.aspx

Photocell has black, white and red wires on photocell.
Black goes to Hot from breaker.
White goes to Neutral from breaker box
Red goes to Load (light)

Electricians don't guess, they test.
You should have one wire coming from breaker box, and another set of wires going to light.
Separate wires for testing.
Since you are outdoors, stand on dry boards and tape tester leads to wood sticks to keep hands away from power.
Turn power ON
Test each wire to bare ground wire.
Tester lights up on hot wire. This wire should be black.
Hot wire connects to photocell black

Hot is identified.
Test Hot wire to all wires except bare ground.
Tester lights up on neutral. This wire should be white.
Neutral wire connects to photocell white

Now the other cable goes to Load. This cable has a black and white wire.
Connect photocell red to black Load wire
Connect white Load wire to Neutral, along with photocell white.

Ground wires are twisted together.

Add a comment for more free help.
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For a price, expert speaks with you over phone while you work on any do-it-yourself project.
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Are you trying to wire a pool pump?
I found manuals at the Haywood site > I saw nothing for K48m2n11b or anything close to that number
http://www.haywardnet.com/inground/products/manuals.cfm

But lets work on the problem and see if I can give you some help:

After opening a few manual and searching for the word 'volt' and 'pump' ... each manual talks about 'pumps' generically, as if the pump is a separate purchase item.

Lower down on the manual page they have a list of pool pumps. A search for the word 'volt' inside the pump manuals says 'match supply voltage to motor nameplate voltage.'

As you know, each electric device has a label showing voltage, wattage, etc. Your pump should show 120Volts or 240V. I didn't see any mention of 3 phase wiring, so I assume your Haywood pump runs on typical residential wiring? And that you are not using 440Volt or 3 phase.

The 120Volt pump will have a black, white and bare ground.
The 240Volt pump will probably have a black, white, red and bare ground
The 240Volt pump could have a black white and bare ground

First the 120V pump:
The 120Volt line from your breaker box will have a black Hot wire, white Neutral wire and bare ground >>> this wire connects color-to-color with pool pump

Next the 240V pump with black, white, red and bare ground
a) The 240Volt line from your breaker box can have the same 4 wires, in which case they connect color-to-color
b) The 240Volt line from your breaker box could have a black white and bare ground, in which case the black goes to black, the white goes to red, the bare coppers are connected, the white pump wire is capped off and not used. If pump does not operate with this wiring, another line from the breaker with wires that match pump might be necessary.

The 240V pump with black white and bare ground
a) The 240Volt line from breaker can have black, white, red and bare ground, in which case the black goes to black, the red goes to white, bare grounds are connected, the white wire is capped off
b) The 240Volt line from from breaker can have black white and bare ground, and this connects color-to-color to the pump

HOW do you know if line from breaker is 120V or 240V?
If you know which breaker wire is connected to, then it's easy
If you do not know which breaker
-turn off power
-separate wires so they can be tested
-use ordinary tester
-stand on dry boards
-tape tester leads to sticks so hands are away from power

-turn on power
-test each wire to bare copper
-tester lights up on Hot wire
-120V line will have 1 Hot wire
-240V line will have 2 Hot wires

EJ341 has 2 wires

Review:
Black goes to Hot wire from breaker box
Red wire goes to Load (light, fan, motor)
White wire goes to Neutral
Green to bare copper ground wire

Orientation:
Your original switch had 2 wires plus bare ground.
One of these wires is Hot, the other goes to Load.
You said original wires are Red and Black

How do you find Hot wire?
-Your original switch had 2 wires.
-Remove timer from box.
-Pull original 2 wires out where you can test them
-Turn on power
-Use regular tester
-Tape tester leads to wood sticks so your hands stay away from voltage
-Power is on
-Test each original wire to bare ground wire
-When tester lights up, that is Hot wire ... this wire connects to Black wire on timer
- The other wire goes to Load so it connects to Red wire on timer

How to test for Neutral wire
Test Hot wire to your white wires - No need to untwist them.
When tester lights up, that is Neutral
White wire from timer connects to Neutral.
Green goes to ground wire.

How to reset timer
I'm not sure which timer you have. Probably GE 15086. Reset is small round button below HOUR button. Use paper clip and push-in reset until timer flashes 12 o'clock.

Yes the voltmeter measures the voltage.
When you power up the computer to test the voltage on the 4 wire connectors.
Test the voltage red and balck wire should read 5 volts.
Test the voltage yellow an black wire should read 12 volts
If the burning smell is from the power supply then most likely a capacitor has blown in the switch mode power supply.
I would advise you purchase a new power supply, do not try and repair it, these mains devices can be dangerous if you don't have knowledge.

Old timer: Intermatic EJ500 & ST01C timers have a battery. Battery operates the clock motor. Red wire is for 3-way circuit [a hallway with 2 switches is a 3-way circuit].

Utilitec timer, clock runs on 120Volt circuit instead of battery. So clock has to have power.

How to connect wires:
Black timer wire connects to hot wire from breaker box.
Red (or blue) timer wire goes to landscape lights.
White timer wire connects to white neutral wire [or if no neutral is available, connect to bare ground wire].
Green timer wire goes to bare ground wire.

How to find black hot wire and white neutral wire inside box: Disconnect and separate wires so you can test. Use ordinary tester. Power is on. There is only 1 black hot wire inside each electrical box. Test each black wire to bare ground until tester light comes on > that identifies the black hot wire. Next, test black hot wire to white wires until tester light comes on > that is the neutral wire. Exception: This test does not necessarily work with 3-way switches since they reverse each time switch is thrown.

is your house older, Some old wires its hard to tell which one is the grounded conductor(nuetral), Both Look black. If this is case You need to test it with a voltage tester- The green and yellow is a ground wire. Test the green with the voltage tester, Along with one of the blacks, if the Black and green set of the voltage tester that black is the hot. hook it up to the black on the lt. hook white to the other black. and green to either green screew or ground wire which ever is provided