Blower motor draw


By Steve Schaeber, MACS Technical Editor

Recently, I posted to the MACS WordPress blog and covered a fuse issue on a 1999 Volkswagen Jetta. In response to my post, I received a comment from reader Bruce Caron. Here’s an excerpt from his message:

As a former VW dealer tech, can I add a bit to your diagnosis? You would have done a better job had you, after replacement of the fuse, used an amp clamp to verify that the blower motor was not drawing an excessive amount of current. Could be maybe a dirty cabin air filter or the blower was just tired? Any time I do a blower motor or have a blown fuse, I will always check the current draw just to be sure.

So to follow up, I decided to go out and check the current draw of the blower motor on that Jetta. After all, that would be the correct way to test the system after fuse replacement and verify it’s operating properly. You may remember from the original post, the fuse was number 25, which is a 25 amp fuse. I’m not exactly sure why it blew in the first place; the system wasn’t working and replacing the fuse fixed it. I normally wouldn’t bother to find out why or verify the repair through ohmmeter testing because the vehicle is 15 years old, and sometimes fuses just blow. In this case, I know the vehicle owner installed a new cabin air filter in July, but I’m not so sure about the motor. So, I did just like Bruce suggested, grabbed my clamp amp and a few hand tools, and went out to the Jetta. Under the glove compartment door there is a soft panel that can be moved out of the way, exposing a brown wire which is the ground for the blower. Engine running, A/C on, fan on high (setting 4) and the meter measured 19.8 amps.

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Image 1: This brown wire is used to ground this Jetta’s blower motor.

To take this diagnostic test a little further, I tested all four fan speeds under two conditions: both with the recirculation button turned on and off. I wanted to see what difference the re-circ would make, if any, but also wanted to see what the difference in current draw would be amongst the different speed settings. Here’s what I found:

Fan Speed           With Recirculation           Without Recirculation

4                              19.8 Amps                           18.0 Amps

3                              11.5 Amps                           10.8 Amps

2                              6.8 Amps                             6.5 Amps

1                              3.9 Amps                             3.8 Amps

 

There are a few things we can learn from this chart. First, at the highest fan speed setting the motor is drawing under 20 amps, which is much less than the 25 amp rating of the fuse. But this chart also tells us a few things about the relationship between blower motor speed, motor current draw and the position of the re-circulation door. Naturally, we would expect to see current draw increase as fan speed increases, but we’re seeing a larger increase when re-circulation is commanded.

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Image 2: It’s relatively easy to connect an amp clamp and measure current draw.

Blower motor amperage is not only affected by fan speed, but also by the load placed on it. The motor is turning fastest with the speed set to 4, but the motor is also working harder when recirculation is turned on, and therefore is drawing more current. That being said, why then is the current draw so much closer together at speed 1? Since the motor is turning so slowly, the application of recirculation does not cause as much of an effect on the motor’s current draw. Sure, it probably is working a little bit harder, but since it’s not moving as fast, the increase in draw is negligible.

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Image 3: The curve of the graph becomes more pronounced as fan speed increases in re-circulation mode.

Want to take this test a step further? Here’s a neat experiment to try: With re-circ turned on, block the air intake with an old shirt or a stiff piece of paper or cardboard, such as from a cereal box. What will happen to the amp reading?

Will it increase or decrease? You might be surprised by what you find. Respond to this blog or send an e-mail to: steve@macsw.org and let me know your results, which we’ll explore in an upcoming MACS WordPress blog.

Thanks for your comments, Bruce!

If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a technical newsletter with information like what you’ve just read in this blog post visit http://bit.ly/10zvMYg for more information.

You can E-mail us at macsworldwide@macsw.org . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.

Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Meet me at MACS Make Connections that Matter, February 5-7, 2015 at the Caribe Royale, Orlando, FL.

Posted in Automotive, Automotive Aftermarket, Automotive training, Electrical/Electronic, Mobile Air Conditioning, Refrigerants | Tagged , , , , , , , | Leave a comment

A customer comes into my shop and says can you make me a hose?


As told to MACS Staff by Marks Air

We received this story from MACS member Gordon Marks at Marks Air in Tampa, FL. Gordon is a frequent contributor to the MACS blog.
A customer came in with his farm tractor on a trailer and said,  “Leroy told him that we could make a hose for his A/C system and that the discharge service valve was leaking.”

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This is a picture of what Marks Air found. Service professionals will appreciate this, if you don’t get it you need to become a MACS member.

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He unloaded the tractor and left it with Marks Air.

In addition, to the hose, the clutch was intermittent and they found that the wiring on the switch (it was an electronic control so the wires were very small) was broken and had to be re-soldered.

There was still low voltage (11.5VDC) so they put a relay in the circuit rather than chasing it.

Oh, we also made a hose, replaced the drier, evacuated and  recharged it. This is a good example of why professional service is important.

If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a technical newsletter with information like what you’ve just read in this blog post visit http://bit.ly/10zvMYg for more information.

You can E-mail us at macsworldwide@macsw.org . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.

Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Meet me at MACS Make Connections that Matter, February 5-7, 2015 at the Caribe Royale, Orlando, FL.

Posted in Automotive, Automotive Aftermarket, Automotive training, Electrical/Electronic, Mobile Air Conditioning | Tagged , , , , , , , , | 1 Comment

1999 VW Jetta – A/C Fuse # 25


By Steve Schaeber, MACS Technical Editor

Technicians working on a third generation Jetta might find their A/C controls totally inop, including no blower fan operation amongst any of the fan speeds, and no operation of the A/C button or recirc button. Even the backlights behind these buttons may not illuminate. A possible cause could be similar to what was found on this 1999 Jetta here at the MACS Garage a few weeks ago.

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Photo 1: Operator’s control panel for this ’99 Jetta has ON/OFF buttons for both AC and Recirc.

 

Fuse # 25 is listed as the “Fresh Air Blower, Climatronic, A/C” fuse, but actually powers most of the A/C control panel as well. When this car came into the shop, the “AC” button on the controls would not light up when depressed. Since the vehicle was recently in for service, and the system was known to be in good working condition, I figured it had to be something other than the mechanical refrigeration circuits. I went right after the fuse panel in the driver’s door jamb to inspect the fuses.

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Photo 2: The cabin fuse panel on the Jetta can be found by opening the driver’s door and removing the access cover.

Before going all out and testing every fuse in the panel, I decided to look up the fuse function arrangement in my service information system. When I found the right chart, I printed out those pages, and using a yellow highlighter, marked all the fuses related to the A/C system. That way, when I took the pages out to the shop to start my testing, I knew exactly which ones to look for. I even highlighted their colors and positions in the panel to make identification easier. The nice thing about taking this extra step is that you can save time by not testing unrelated fuses, and go right to the potential problem areas.

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Photo 3: A yellow highlighter indicating the fuses to test makes the job easier out in the shop.

Turns out that fuse # 25 was the culprit, and a new fuse took care of this problem. The vehicle owner was happy to again have a working blower motor, not so much for use with the A/C system (2014 has given us a rather mild August), but primarily because of the potential safety issue surrounding an inoperable windshield defogger. It’s still working in this daily driver now, all these weeks later, so we’ll call this one fixed.

Have a similar repair you’d like to share with MACS? Drop me a line to steve@macsw.org and share your story.

If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a monthly technical newsletter with information like what you’ve just read in this blog post and much more visit http://bit.ly/10zvMYg for more information.

You can E-mail us at macsworldwide@macsw.org . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.

Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Meet me at MACS Make Connections that Matter, February 5-7, 2015 at the Caribe Royale, Orlando, FL.

Posted in Automotive, Automotive Aftermarket, Automotive training, Electrical/Electronic, Mobile Air Conditioning, Refrigerants | Tagged , , , , , , , , | Leave a comment

What is the state of the mobile A/C industry?


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State-of-the MAC Industry on Saturday, February 7, 2015

One of the programs during the 2015 MACS Training Event and Trade Show will feature  a luncheon presentation on Saturday,  February 7 with MACS technical advisor Ward Atkinson, who will explore the potential impact of multiple refrigerants and new regulations on the mobile A/C vehicle manufacturer and service industry, and ask the question “will history repeat itself?” Atkinson points out that, “Many replacement refrigerants were offered for use in the transition from R-12, causing many concerns, but history records that less than 10 percent of the R-12 fleet was ever retrofitted to use another refrigerant.”

EPA has recently proposed a rule which would phase out many of the currently listed SNAP refrigerants, and most significantly, would prohibit the use of R-134a in new, light-duty vehicles starting with model year 2021. Under the proposed rule, production and service use of R-134a is not restricted.

Under the EPA rules new vehicle MAC system use requirements for R-1234yf, R-744 (carbon dioxide), R-152a, and possibly new blend refrigerants, could all play a role in the transition.

The phase down of R-134a is occurring more slowly than the previous transition from R-12, and given there is more time, the industry should take advantage of this opportunity to plan better for the changes to come.

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Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Meet me at MACS Make Connections that Matter, February 5-7, 2015 at the Caribe Royale, Orlando, FL. Registration is now open at this link or call the MACS office at 215/6331-7020.

If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a technical newsletter with information like what you’ve just read in this blog post visit http://bit.ly/10zvMYg for more information.

You can E-mail us at macsworldwide@macsw.org . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.

 

Posted in #1234yf, Automotive, Automotive Aftermarket, Automotive training, Mobile Air Conditioning, Refrigerants | Tagged , , , , , , | Leave a comment

Do you know how to defend your repair turf?


You fix an air conditioning leak, recharge the system, and shortly thereafter the motorist is back, complaining that he turned on the A/C, the engine soon started to run rough and
the Check Engine light came on and is still on. And on most cars, the A/C probably stopped working.

Sure enough, that’s what happened. However, unless you did something on the order of installing a new powertrain computer, throttle position sensor or other parts in that area,
your repair of the A/C just brought the symptom to the fore.
All late models (OBD II) have “misfire monitors,” power-train computer algorithms (software strategies) that not only log misfire, but (if applicable) can narrow it to individual cylinders. A/C puts a huge load on the engine, so a borderline spark plug or its wire, or fuel injector, misbehavior in the idle air valve, or a borderline sensor, can cause the engine to misfire. When the A/C wasn’t working, there was no
compressor pumping load to produce the symptom, and in your shop the cooling load was low or the misfire monitor algorithm did not reach the trigger stage. When the monitor
does set, it not only turns on the Check Engine light, but also
may turn off the A/C compressor. In some cases the misfire is so barely noticeable that the motorist doesn’t even associate it with the Check Engine light, but when he turned on
the A/C, he notices it stopped cooling (on those cars where misfire codes disable A/C).

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How do you convince the motorist it wasn’t your fault?
Unless he or she is reasonably savvy in this area, the sad answer is “not easily.” It helps if the Check Engine light is accompanied by a misfire code, which is PO300. Although a cracked or improperly tightened A/C compressor bracket may cause idle roughness when the A/C is turned on, it won’t illuminate the Check Engine light or log a trouble
code. However, if the A/C repair did involve a powertrain
component, or if you may have loosened a wire while working under-hood, you are going to have to find the problem.

If you don’t have a scan tool that works on late models with CAN (Controller Area Network) data bus, so you can get the misfire or other code that absolves you of blame,
you’ll surely have to pay a dealer or aftermarket drive-ability specialist for a diagnosis. You may not get the answer from a scan tool every time, but if you aren’t able to at least do that, you can find yourself in a nasty dispute.

The inter-relationship of all systems on the car means you
have to be able to at least defend your turf.

If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a technical newsletter with information like what you’ve just read in this blog post visit http://bit.ly/10zvMYg for more information.

You can E-mail us at macsworldwide@macsw.org . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.

Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Meet me at MACS Make Connections that Matter, February 5-7, 2015 at the Caribe Royale, Orlando, FL.

Posted in Automotive, Automotive Aftermarket, Automotive training, Electrical/Electronic, Mobile Air Conditioning, Refrigerants, Uncategorized | Tagged , , , , , , , , , , | Leave a comment

Registration is now open for MACS 2015 Training Event and Trade Show


Meet me @ MACS – Make Connections that Matter

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Registration is now open for the ultimate, total vehicle climate and thermal management, 3-day, live training event delivered by the best instructors in the business. The Mobile Air Conditioning Society (MACS) Worldwide will hold its 2015 Training Event and Trade Show, February 5-7, 2015 at the Caribe Royale All Suite Hotel and Convention Center in Orlando, FL.

“We are very pleased so many MACS member companies are sending their best instructors to make our 2015 training event such a powerful and valuable technical program,” expressed Elvis L. Hoffpauir, MACS president and chief operating officer. “We are also excited that Robert L. Darbelnet, president of AAA, who has a great understanding of the service and repair business will deliver our Keynote address. We are also honored to have representatives from Chrysler, Ford, General Motors and Toyota delivering presentations at our general session before we kick-off our day-long trade show. MACS has a busy schedule planned and, I truly believe something for everyone who wants to grow their business and grow personally.”

In addition, adjacent meetings will be held by the Interior Climate Control Committee of SAE International on Thursday, February 5th and the Car Care Council Women’s Board will be holding their Winter Leadership Conference on Wednesday, February 4 and Thursday, February 5.

The entire schedule for the MACS 2015 Training Event and Trade Show can be found on the MACS website at www.macsw.org . Registration can be completed online or by phone at 215/631-7020 x 0 and by fax at 215/631-7017.

Hotel reservations can be made for the Caribe Royale All Suite Hotel and Convention Center through a custom link on the MACS website or by phone at 888/258-7501. MACS room rate is $155 per night plus tax for a suite. The room rate cut-off date is January 6, 2015.

Posted in Automotive, Automotive Aftermarket, Automotive training, Mobile Air Conditioning, Refrigerants | Tagged , , , , , , , | Leave a comment

Become a member of MACS


If you’re an independent service shop owner performing engine cooling and mobile A/C service and repairs.

Ask yourself who is backing you up everyday with resources like accurate technical information, the latest info on federal regulations for your business, a free service help hotline, access to discounted health insurance and business plans, discounts from CINTAS and many more vendors? Anybody?

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The Mobile Air Conditioning Society (MACS) Worldwide values your engagement and we invite you to become a MACS member . Please take a moment to read the enclosed brochure for a look at MACS’ exclusive, money-saving, membership benefits and see why MACS membership doesn’t cost- it pays.

Longtime MACS member Chuck Braswell of Rocky Mount Radiator and A/C recently sent us this comment:

“I just finished reading the August 2014 MACS Service Report by Dave Hobbs. EXCELLENT INFO. This is needed and certainly an area of concern at my shop. When you don’t use a voltmeter every day, each job becomes a “re-learn” procedure for the technician, which costs someone extra money (usually the shop owner).”
MACS also invites you to visit the MACS website at http://www.macsw.org and visit our membership page for details on membership benefits. For instance, did you know we now have a free prescription discount card available to members and their employees through our affinity insurance provider?

What kind of people become members of MACS? Click here to view a list of our newest members.

In addition, MACS hosts the best of live training mobile A/C and engine cooling training event and trade show. Join us February 5-7, 2015 for MACS Training Event and Trade Show at the Caribe Royale All Suite Hotel and
Convention Center in Orlando, FL. Members also save substantially on registration fees for this event.

We are always available to discuss your ideas and questions.

 

Sincerely,

The MACS staff!

Call us at 215/631-7020 x 304 email us at membership@macsw.org
Visit our website at www.macsw.org

 

Posted in Automotive, Automotive Aftermarket, Automotive training, Mobile Air Conditioning | Tagged , , , , , | Leave a comment

Sometimes, if it ain’t broke…


It’s easy for technicians to be misled by temperature and pressure readings, and what they think should be happening as a result of what they see. A high-mileage thirteen-year-old Mazda 626 isn’t cooling on an 85-degree day in New England. The technician finds that the low-pressure switch isn’t working, replaces it, and although the center register air temperature drops to 40 degrees, the clutch doesn’t cycle and the A/C pressures are 150 and 40 psi at idle. The technician decided that since it was a cycling clutch system, it had to cycle sometime, but he kept watching, and it wouldn’t.

 

The high-side pressure looked low and the low side looked high, possibly indicating a weak compressor or expansion valve stuck partly open. He also was ready to decide to look for a defective evaporator fin sensor, but the cooling performance was good and
the system wasn’t icing up, so a defective fin sensor wouldn’t make sense. Finally, he got the word that in high humidity (not the usual condition in the area), the system may not cycle, certainly not if the compressor can’t pull the suction side well below 40 psi. Might the  compressor be a bit weak, might the pressure gauge readings be off, might the thermometer reading be optimistically low? Sure, but if the air is cold – and cool
air on the driver’s face is pretty obvious, don’t think
too much.

If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a technical newsletter with information like what you’ve just read in this blog post visit http://bit.ly/10zvMYg for more information.

You can E-mail us at macsworldwide@macsw.org . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.

Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Meet me at MACS Make Connections that Matter, February 5-7, 2015 at the Caribe Royale, Orlando, FL.

Posted in Automotive, Automotive Aftermarket, Automotive training, Mobile Air Conditioning, Uncategorized | Tagged , , , , , , , , | Leave a comment

Download the September/October issue of ACtion Magazine


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DOWNLOAD the digital issue of MACS  September/October 2014 ACTION Magazine to your desktop of mobile device. It is packed with great information and the just released program for MACS 2015 Training Event and Trade Show.

Posted in Automotive Aftermarket, Automotive training, Mobile Air Conditioning, Refrigerants | Tagged , , , , , , , , , , | Leave a comment

When you assign an A/C job to a non specialist


If your shop’s A/C  specialist is busy and you want to get the diagnosis started, you can assign the preliminaries to any technician in the shop. Here is what GM asks a technician to be able to provide when he calls in with an A/C  performance problem:

•  A/C  high and low side pressures.
•  Inside temperature sensor reading.
•  Outside temperature sensor reading
•  Evaporator temperature sensor reading (if
used).
•  Duct temperature sensor reading (if used).
•  A/C  refrigerant charge level.

This is actually  a  tough  one, because we ask, how canhe tell? We’ve said many times that the pressures  won’t  tell  you,  although  if  very  low, could be an indication. MACS recommendation (as it’s been for years) is to use an SAE J2788 recovery/recycle/recharge  machine  and  see how much refrigerant it pulls out.

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Assuming you’ve  been  checking  the  scale  calibration, the machine should produce a number that’s accurate, and if the charge was correct, that number should be 95% or more of what’s supposed to be in the system.

If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a technical newsletter with information like what you’ve just read in this blog post visit http://bit.ly/10zvMYg for more information.   Visit the MACS website at www.macsw.org or email info@macsw.org   

You can E-mail us at macsworldwide@macsw.org . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.

Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Meet me at MACS Make Connections that Matter, February 5-7, 2015 at the Caribe Royale, Orlando, FL.

Posted in Automotive, Automotive training, Mobile Air Conditioning, Refrigerants | Tagged , , , , , , | Leave a comment