Quantcast
Jump to content

Pulsing Voltage To A/C Compressor, 02 VW Jetta


Recommended Posts










A 2002 VW Jetta arrived at our shop the other day, the customer complaint…no air conditioning. The system was fully charged so we started our diagnostic tests and found that there was a pulsing voltage to the a/c clutch. The fan control module would pulse a 12 volt signal every few seconds.

 

After a little research we learned that a faulty compressor clutch could be the fault. We ohmed the clutch coil and found it open. We replaced the compressor clutch and now the FCM sends a constant 12 volt signal and all is ok.

 

Maybe others have seen this, but it stumped me and my lead tech at first. Apparently, if there is a problem with the clutch coil, the voltage will pulse from the FCM.

 

It's a good thing we did a little research to find how the system works before shot-gunning the problem.

 

 

I've run across that one before, but, I have one problem I've found with the newer beetles that will throw you a curve ball... If you get a Beetle with A/C problems... do this little test first.

With the car idling and A/C on... and you get no cold air... BUT... if you bring the engine rpms up to say... 2 grand or so ... if now you have perfect cold air the problem is not the A/C ... it's the charging system. The feedback current from the alternator is too low at idle for the PCM to recognize that the charging system is working. However, it is high enough to keep the charge light off. The PCM reacts by assuming the charging system is shot and starts shutting down accy systems to avoid overloading itself.

To make matters worse... everytime I ran across this problem I have never been able to see a voltage change at the battery with a meter. But, believe me... it's the alternator. The last one I did was probably the worst one. Everything looked great, but I changed the alternator anyway. As soon as I did... the A/C kicked on... blowing cold air just like you would expect.

Hope this helps... Gonzo

Edited by Gonzo
Link to comment
Share on other sites

That's a great tip, Gonzo. Maybe we should post more of our technical war stories. Afterall, if we can help each other to become more profitable in the shop, it helps our business.

 

let's do...

Link to comment
Share on other sites

  • 8 months later...

I've run across that one before, but, I have one problem I've found with the newer beetles that will throw you a curve ball... If you get a Beetle with A/C problems... do this little test first.

With the car idling and A/C on... and you get no cold air... BUT... if you bring the engine rpms up to say... 2 grand or so ... if now you have perfect cold air the problem is not the A/C ... it's the charging system. The feedback current from the alternator is too low at idle for the PCM to recognize that the charging system is working. However, it is high enough to keep the charge light off. The PCM reacts by assuming the charging system is shot and starts shutting down accy systems to avoid overloading itself.

To make matters worse... everytime I ran across this problem I have never been able to see a voltage change at the battery with a meter. But, believe me... it's the alternator. The last one I did was probably the worst one. Everything looked great, but I changed the alternator anyway. As soon as I did... the A/C kicked on... blowing cold air just like you would expect.

Hope this helps... Gonzo

 

On these cars check voltage output in ECU measuring blocks. I've seen a number of odd problems caused by voltage issues on VW/Audi cars and Benz's. A new regulator solves the problem. I often have it on the top of my list to check voltage and alternator output and ripple when diagnosing drive-ability or anything that stumps me at first. I do forget sometimes. Had a Chrysler in here the other day with erratic idle and instrument cluster quirks, luckily stumbled on the negative terminal being loose, a quick clean and tighten solved all the problems.

 

Haven't stumbled upon this A/C problem yet but its that time of year now so I'll keep it in mind.

Link to comment
Share on other sites

A 2002 VW Jetta arrived at our shop the other day, the customer complaint…no air conditioning. The system was fully charged so we started our diagnostic tests and found that there was a pulsing voltage to the a/c clutch. The fan control module would pulse a 12 volt signal every few seconds.

 

After a little research we learned that a faulty compressor clutch could be the fault. We ohmed the clutch coil and found it open. We replaced the compressor clutch and now the FCM sends a constant 12 volt signal and all is ok.

 

Maybe others have seen this, but it stumped me and my lead tech at first. Apparently, if there is a problem with the clutch coil, the voltage will pulse from the FCM.

 

It’s a good thing we did a little research to find how the system works before shot-gunning the problem.

 

 

Sounds they are using a current detecting transistor in the output from the module, either that or they are monitoring the feedback diode for current load and if the system sees a out of spec condition it will refuse to power the circut.

 

I'd have to check the diagram but this AC clutch was not relay drive ?

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Have you checked out Joe's Latest Blog?

         3 comments
      Got your attention? Good. The truth is, there is no such thing as the perfect technician pay plan. There are countless ways to create any pay plan. I’ve heard all the claims and opinions, and to be honest, it’s getting a little frustrating. Claims that an hourly paid pay plan cannot motivate. That flat rate is the only way to truly get the most production from your technicians. And then there’s the hybrid performance-based pay plan that many claim is the best.
      At a recent industry event, a shop owner from the Midwest boasted about his flat-rate techs and insisted that this pay plan should be adopted by all shops across the country. When I informed him that in states like New York, you cannot pay flat-rate, he was shocked. “Then how do you motivate your techs” he asked me.
      I remember the day in 1986 when I hired the best technician who ever worked for me in my 41 years as an automotive shop owner. We’ll call him Hal. When Hal reviewed my pay plan for him, and the incentive bonus document, he stared at it for a minute, looked up, and said, “Joe, this looks good, but here’s what I want.” He then wrote on top of the document the weekly salary he wanted. It was a BIG number. He went on to say, “Joe, I need to take home a certain amount of money. I have a home, a wife, two kids, and my Harly Davidson. I will work hard and produce for you. I don’t need an incentive bonus to do my work.” And he did, for the next 30 years, until the day he retired.
      Everyone is entitled to their opinion. So, here’s mine. Money is a motivator, but not the only motivator, and not the best motivator either. We have all heard this scenario, “She quit ABC Auto Center, to get a job at XYZ Auto Repair, and she’s making less money now at XYZ!” We all know that people don’t leave companies, they leave the people they work for or work with.
      With all this said, I do believe that an incentive-based pay plan can work. However, I also believe that a technician must be paid a very good base wage that is commensurate with their ability, experience, and certifications. I also believe that in addition to money, there needs to be a great benefits package. But the icing on the cake in any pay plan is the culture, mission, and vision of the company, which takes strong leadership. And let’s not forget that motivation also comes from praise, recognition, respect, and when technicians know that their work matters.
      Rather than looking for that elusive perfect pay plan, sit down with your technician. Find out what motivates them. What their goals are. Why do they get out of bed in the morning? When you tie their goals with your goals, you will have one powerful pay plan.
  • Similar Topics

    • By Joe Marconi

      Premium Member Content 

      This content is hidden to guests, one of the benefits of a paid membership. Please login or register to view this content.

    • By DUFRESNES

      Premium Member Content 

      This content is hidden to guests, one of the benefits of a paid membership. Please login or register to view this content.

    • By Changing The Industry
      The Basics of Owning An Auto Repair Shop - Part 3
    • By carmcapriotto
      Live from MACS (Mobile Air Climate Systems) 2024 Training Event & Trade Show, Michael Ingvardsen discusses the evolution of thermal heat management, the importance of training, and the challenges of new refrigerants. Michael emphasizes the need for compatibility between components and refrigerants, and the role of distributors in ensuring product reliability. The episode highlights the complexity of modern air conditioning systems and the value of specialized knowledge in the field. Michael Ingvardsen, Global Technical Training Manager, Nissens Automotive Show Notes
      Importance of training and industry legacy (00:02:05) Michael discusses the significance of training, family legacy in the industry, and the need to understand the past for the future. Changes in automotive air conditioning (00:06:08) Michael explains how air conditioning technology has changed, emphasizing the impact on vehicle components and functionality. Heat pumps in electric and hybrid vehicles (00:10:15) Michael explains the role of heat pumps in electric and hybrid vehicles. Refrigerant and technology standards (00:13:34) Discussion on the impact of refrigerant standards, environmental considerations, and the need for understanding chemical and refrigerant properties. Future refrigerant technology (00:17:33) Insights into future refrigerant technology, including the challenges and considerations for electric vehicles and heat pump systems. The challenge of introducing new refrigerants (00:18:29) Discussion on the challenges of introducing replacement refrigerants. Importance of air conditioning training (00:22:51) Emphasis on the value of staying updated with air conditioning training and the upcoming training classes on heat pumps. Challenges in implementing new practices (00:32:47) Discussion on the challenges in getting technicians to adopt new practices and the need for proper training and information dissemination. The impact of improper maintenance on warranties (00:30:58) The implications of improper maintenance on heat pump systems and the financial consequences for shops. The need for compliance and best practices (00:34:36) Emphasis on the importance of following proper procedures and best practices in air conditioning maintenance to avoid potential breakdowns and higher costs.
      Thanks to our Partner, NAPA Auto Care Learn more about NAPA Auto Care and the benefits of being part of the NAPA family by visiting https://www.napaonline.com/en/auto-care Connect with the Podcast: -Follow on Facebook: https://www.facebook.com/RemarkableResultsRadioPodcast/ -Join Our Private Facebook Community: https://www.facebook.com/groups/1734687266778976 -Subscribe on YouTube: https://www.youtube.com/carmcapriotto -Follow on LinkedIn: https://www.linkedin.com/in/carmcapriotto/ -Follow on Instagram: https://www.instagram.com/remarkableresultsradiopodcast/ -Follow on Twitter: https://twitter.com/RResultsBiz -Visit the Website: https://remarkableresults.biz/ -Join our Insider List: https://remarkableresults.biz/insider -All books mentioned on our podcasts: https://remarkableresults.biz/books -Our Classroom page for personal or team learning: https://remarkableresults.biz/classroom -Buy Me a Coffee: https://www.buymeacoffee.com/carm -The Aftermarket Radio Network: https://aftermarketradionetwork.com -Special episode collections: https://remarkableresults.biz/collections    
      Click to go to the Podcast on Remarkable Results Radio
    • By Changing The Industry
      Episode 151 - A Shop Owner's Guide to Consolidation and Exit Strategies


  • Our Sponsors



×
×
  • Create New...