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Farm Machinery Digest: Testing your diagnostic skills: Alternator belts

Ray Bohacz for Progressive Forage Published on 09 July 2021

Situation No. 1

You just finished changing the alternator on the haybine and are happy that it can now go back to work, cutting the alfalfa before the rain hits tomorrow.

It is a beautiful day, and you have the AC running and are listening to the Idle Chatter podcast when suddenly the charge light comes on and the audible warning chimes. You stop the machine and open the hood. The belt is lying there – thankfully not cut up but off the pulleys.

You call home for your wife to bring the service truck to the hedgerow and drive over there to wait for her. You think you must have forgotten to tighten the alternator bolts, but when she arrives and you grab the wrench, the bolts are all tight. Why did the belt fall off?

A. Farmer A claims you put the belt back on in a different direction, so it came off.

B. Farmer B states that the bolts came loose on the alternator, and they just seemed tight to you with the wrench.

C. Farmer C says some alfalfa must have gotten on the pulley and walked the belt off.

D. Farmer D believes the bearing in the rebuilt alternator is not good and causing excessive vibration.

Situation No. 2

Your “neck of the woods” is enduring a summer heat wave, and you are glad for an excuse to get back in your truck and run the air conditioner. The cab is extremely hot, so as soon as the engine fires, you put the AC selector to max and head back to the farm, a 10-mile ride. You quickly notice the duct discharge temperature is not that cold. The truck is only a week old, and it was much cooler outside when you took delivery of it, and the AC seemed fine. You say to yourself, “Oh boy, a problem already.”

The next day, over at the grain elevator, the guys ask how you like your new pickup. You said you loved it until it took a long time to cool the cab yesterday. You mention this to some friends, and these are their thoughts.

A. Farmer A asks whether you had the selector on max or normal. He said that if it is on max, that was the problem.

B. Farmer B told you it was so hot that day you cannot blame the truck. He said to be happy it was cooler in the cab than outside.

C. Farmer C believes that the truck will be a lemon, and you should bring it back.

D. Farmer D chimes in that the system is low on refrigerant.

Situation No. 3

You are searching for a used semi to add to your harvest fleet. You came across a nice International Lone Star with the Maxx Force engine. It interested you since it was a Tier 4 model but did not use DEF and the SCR system like the other brands you looked at. This engine uses EGR only. How could this be? You ask some guys after church, and they tell you.

A. Farmer A says he never heard of that, and all his trucks run a Detroit, and they all use DEF.

B. Farmer B agrees with Farmer A, but he runs Cummins power. He believes the truck must be from Canada, and you may have trouble getting tags in Nebraska.

C. Farmer C says he thinks some engines can be legal with only EGR.

D. Farmer D believes the SCR system is there but does not use DEF.


Situation No. 1: Farmer A is correct. When removing a used drive belt and planning to put it back into service, the rotation direction needs to be marked before it is removed. A belt will have the molecular structure take the form to the direction the load is applied to. If installed the other way, it will stretch prematurely or break. The belt usually stretches and jumps off the pulley, as on the subject haybine.

Mark the belt with a paint pen before removing it, and then it will go back on in the proper rotation and stay there.

Situation No. 2: Farmer A is correct. An AC system can take the air from either the atmosphere (outside) or in the vehicle or cab. When in the normal setting, the outside air is cooled and then sent to the vehicle or cab. In the max or recirc mode, the inside air is cooled.

The proper procedure is to open the windows first with the AC on normal. This will let the temperature in the vehicle normalize with the ambient temperature. Then close the windows and leave the AC on normal. Once the interior temperature drops below the ambient temperature, you can now cool the inside air.

When you put the system on max or recirc first, you are trying to cool air that may be nearly 100 degrees hotter than the ambient air since the vehicle was parked in the sun with the windows closed.

Situation No. 3: Farmer C is correct. Both EGR (exhaust gas recirculation) and SCR/DEF (selective catalytic reduction/diesel exhaust fluid) are used to control an emission called oxides of nitrogen (NOx). The EPA only cares about the engine manufacturer meeting the standard and not how they go about it.

The Maxx Force engines tried for a while to not use SCR/DEF and employed an extremely high rate of EGR that ended up being a problem if the truck owner was not good about service.

Most but not all Tier 4 Final engines use EGR and SCR.  end mark

Email “The Hotrod Farmer” Ray Bohacz with your machinery-related questions. Visit his site – Farm Machinery Digest  – for technical articles and to listen to his Idle Chatter podcast, which has listeners in 67 countries. Also tune into Farm Machinery Digest Radio on Sirius/XM Channel 147.

Ray Bohacz
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