Treadmil stops or slows down upon walking.

Unplug unit remove motor shroud then plug unit back in , press start and begin walking on the belt normally and try to stall the belt to make it slip ( planting foot to stop the belt).
Be careful during this test. If the problem is in the drive belt, either the drive belt will stop when stalled or the front roller will stop when stalled. Here is the procedure for adjusting the drive belt.
Find the motor mounts. Many motors in Icon treadmills have a main pivot joint in which a bolt runs the full length of the motor mount. This bolt will require loosening to provide maximum adjustability. Some models have a single jack bolt and others have an auto tensioner. Single jack bolts are the easiest to adjust.
Find the set bolt(s) on the motor. This is typically run through only one side of the motor mount or may be on both sides but it does not run the full length of the mounting. Loosen this bolt(s) but do not remove. Jack bolt models will have flat mounts and may contain up to four bolts.
Look for a bolt that will tension the motor. If it has this bolt, it typically runs in the same direction parallel with the drive and walking belts. If your treadmill is not equipped with this bolt, skip to Step 4. If your treadmill is equipped with this bolt (very few are) the repair will only require one person. Using 2 7/16" wrenches, make a few turns to this bolt, tighten the bolts and test your treadmill for slipping. If belt continues to slip, and if their is too much tension ( you should be able comfortably twist the drive belt 90 degrees ) then replace drive belt. If the motor, drive belt, and front roller continue to turn when the walking belt is stalled, the problem is with the walking belt slipping on the front roller, here the procedure adjusting the walking belt.
If the walking belt slips when walked on, first remove the key and UNPLUG THE POWER CORD. Using the allen wrench, turn both rear roller bolts clockwise, 1/4 of a turn.When the walking belt is correctly tightened, you should be able to lift each side of the walking belt 3 to 4 inches off the walking platform. Be careful to keep the walking belt centered. Plug in the power cord, insert the key and carefully walk on the treadmill for a few minutes. Repeat until the walking belt is properly tightened
If the drive belt continues to turn but the front roller stalls, you may have a broken front roller pulley. If this is the problem, you will notice it because the plastic will usually make a loud squealing sound on the metal front roller. The front roller assembly will need to be replaced and the drive belt must be replaced also. We suggest replacing the drive belt as well because it is a low cost item and will most likely, have suffered unusual wear from the problem. Another possibility is that the drive belt has worn down. In some cases, belt dressing may help correct the problem. If not, the drive belt must be replaced.

Walking Belt is Worn: The only certain way to test for a worn walking belt is to take a DC amp draw (if you have a DC treadmill) or an AC draw (for AC). Trying to look at the belt or a feel test is highly unreliable. Better tests, if you lack a DC ammeter (they are expensive for a good one), are a coast test or an incline test. The coast test is to get on the treadmill as the lowest incline setting and walk on the treadmill at 3 MPH. Pull the safety key and it should take you 2-3 full steps to stop (this is a general rule…some like a few Tunturi models stop on a dime even with a healthy belt but for most models, this tests works well upon). Fewer steps indicate high friction. The incline test is to put the treadmill at max incline and walk on it at 3 MPH. If the treadmill operates normally at max incline but bogs down at minimum incline, replace the walking belt. Gravity takes over for the drive system eliminating much of the friction problem. On some heavily worn walking belts, this test will not eliminate the problem. Go to your local hard ware store and purchase silicone spray. Apply Lubricant by lift one side of the running belt spray contents length wise starting at motor shroud to the back end repeat this process on the other side. If this unit bogs down again then you will have replace the running belt and possibly the deck

Press the Stop and the Speed Up keys down while inserting the safety key.
Press the Stop key one time. The Time window should read EP:2P. Some newer models may also say FP, Pass, or the like. This means that it passes the EPROM test.
Press either incline key and the incline will calibrate automatically.
BE CAREFUL, THE TREADMILL WILL RUN AT FULL SPEED IN THIS NEXT MODE! DO NOT STAND ON THE WALKING BELT. Press the Speed Up key and hold it down until 85 is shown in the Distance window (some models may show the 85 number in another window).
If the top speed of the treadmill does not match the displayed speed on the computer console, adjust the max speed potentiometer (pot) on the motor control board. This is the board that the red and black motor wires connect directly into in the motor area. The Max Speed pot is clearly labeled. The max speed potentiometer is a small square with a mobile center and is located in one corner of the board and is labeled MAX SPD. It is near the harness that carries the speed signal labeled H,W,L. Using a small insulated screwdriver adjust this potentiometer clockwise to speed up and counter-clockwise to slow down the max speed of the treadmill. A tiny turn of this potentiometer will make a big difference in speed so be careful when making adjustments. It is not important to get the speed set exactly at the max speed of the treadmill but do make sure to get the speed within .2 MPH of the max speed of the treadmill. For instance if the max speed of the treadmill is 10 MPH, make sure to have the speed set between 9.8 MPH and 10.2 MPH. Some models have a 12 MPH top speed, so please check your manual if you aren’t sure. THIS IS A VERY IMPORTANT STEP BECAUSE YOU WILL GET AN ERROR MESSAGE IF THIS STEP IS SKIPPED. After completing calibration of the speed, press the Speed Down key. The treadmill will automatically return to 0 MPH. Please allow the unit to stop completely before continuing. Press the Stop key once and remove the safety key.

Hi James
Unplug unit remove motor shroud then plug unit back in , press start and begin walking on the belt normally and try to stall the belt to make it slip ( planting foot to stop the belt).
Be careful during this test. If the problem is in the drive belt, either the drive belt will stop when stalled or the front roller will stop when stalled. Here is the procedure for adjusting the drive belt.
Find the motor mounts. Many motors in Icon treadmills have a main pivot joint in which a bolt runs the full length of the motor mount. This bolt will require loosening to provide maximum adjustability. Some models have a single jack bolt and others have an auto tensioner. Single jack bolts are the easiest to adjust.
Find the set bolt(s) on the motor. This is typically run through only one side of the motor mount or may be on both sides but it does not run the full length of the mounting. Loosen this bolt(s) but do not remove. Jack bolt models will have flat mounts and may contain up to four bolts.
Look for a bolt that will tension the motor. If it has this bolt, it typically runs in the same direction parallel with the drive and walking belts. If your treadmill is not equipped with this bolt, skip to Step 4. If your treadmill is equipped with this bolt (very few are) the repair will only require one person. Using 2 7/16" wrenches, make a few turns to this bolt, tighten the bolts and test your treadmill for slipping. If belt continues to slip, and if their is too much tension ( you should be able comfortably twist the drive belt 90 degrees ) then replace drive belt.
If the motor, drive belt, and front roller continue to turn when the walking belt is stalled, the problem is with the walking belt slipping on the front roller, here the procedure adjusting the walking belt.
If the walking belt slips when walked on, first remove the key and UNPLUG THE POWER CORD. Using the allen wrench, turn both rear roller bolts clockwise, 1/4 of a turn.When the walking belt is correctly tightened, you should be able to lift each side of the walking belt 3 to 4 inches off the walking platform. Be careful to keep the walking belt centered. Plug in the power cord, insert the key and carefully walk on the treadmill for a few minutes. Repeat until the walking belt is properly tightened
If the drive belt continues to turn but the front roller stalls, you may have a broken front roller pulley. If this is the problem, you will notice it because the plastic will usually make a loud squealing sound on the metal front roller. The front roller assembly will need to be replaced and the drive belt must be replaced also. We suggest replacing the drive belt as well because it is a low cost item and will most likely, have suffered unusual wear from the problem. Another possibility is that the drive belt has worn down. In some cases, belt dressing may help correct the problem. If not, the drive belt must be replaced.

If belt hesitates or slips when walking on unit it may be caused by either a loose walking belt or a loose drive belt. To determine the cause perform the following test: Stand beside Tread-Climber® fitness machine and set speed to 2 MPH. Step on one treadle and attempt to stop movement. If one belt stops but roller at rear and other belt continue to turn walking belt tension should be adjusted. If both belts stop but motor is still turning the drive belt tension should be adjusted.
Adjust walking belt tension at the front of the unit using the provided hex wrench on the exposed adjustment bolts located on each side of each front roller. Be sure to adjust both bolts on each roller the same amount as to not disrupt belt alignment. Tighten (turn clockwise) each adjustment bolt in full turn increments. After each adjustment, restart unit and check to see if belt slippage has been eliminated. Repeat if necessary.

Unplug the unit remove the motor shroud inspect the drive belt if the rubber feel slick then my recommendation is to replace the drive belt. Adjusting the drive belt may take care of the problem if you do not need to adjust it too tight. If you choose to do the adjusting and feel you have adjusted the running belt thinking it would resolve the slipping, then back the tension down until it the running belt is slipping then adjust until the slippage is resolved.

If the walking belt is overtightened, treadmill performance may decrease and the walking belt may become damaged. Remove the key and UNPLUG THE POWER CORD. Using the hex key, turn both idler roller bolts counterclockwise, 1/4 of a turn. When the walking belt is properly tightened, you should be able to lift each edge of the walking belt 3 to 4 in. (8 to 10 cm) off the walking platform. Be careful to keep the walking belt centered. Then, plug in the power cord, insert the key, and run the treadmill for a few minutes. Repeat until the walking belt is properly tightened. . If the walking belt still slows then lubricate running deck the lube may be purchased from iconfitness.com

The walking belt slows when walked on the walking belt maybe overtightened, treadmill performance may decrease and the walking belt may become damaged or the opposite the drive and /or running belt may need tightening. Last thing would be that the belt needs lubrication to be applied between belt and deck.

I believe under the motor shroud on the circuit board their should be 2 pots 1 adjusts torque 2. adjusts speed try adjusting them and see if that take care of the problem if not. worse case it might be the drive motor.

I had simillar problem. I have proform 830 QT. My trademill stops after 10 minutes of work out. Everything shuts down and the circuit breaker pops out.

Root cause:- no lubrication under walking belt. Caused the moter to over work (over heat) and hence te circuit breaker popped out to prevent blowing of motor.

Solution:- Apply the lubricant under walking belt and adjust the belt tension if needed.

Back ground:- Contact proform customer service at 1-888-533-1333 (http://www.iconservice.com/proform/faq_tread.html) and buy the treadmil cleaning kit or lubricant kit which comes with a wand for easy application. It may cost you 35 dollars including shipping. If you need to fix your treadmil right away, use NAPA silicon spray 8300. Proform actually tells do not use it as it may damage your belt. However the specialst who came to fix my treadmill just sprayed it and collected 100 dollars. When I called proform they told me lubricating will fix it and its my mistake to not trust them. I guess they knew exactly what they were saying.