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What was the final diagnosis and fix then?

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Hi,

 

OK, there will be two versions of the how we fixed my AC problem, a short version and a long version.  Hopefully this will help all those other IQ owners that appear to be experiencing the same problem as I did.

 

Background

 

Regassed IQ continued to not engage the magnetic clutch when the AC button was depressed.  The On-Board diagnostics (Hold Auto and Recirculate whilst initiating Ignition) reported Code 79.

 

Short version

 

Its fixed!!!

 

 

OK, smidgeon longer Short version

 

My Flow Control sensor was working within Tolerance but not within Operational Parameters, this prevented the Magnetic Clutch from engaging whenever the AC button was depressed.

 

On the IQ the Flow Sensor is sadly not consumable or replaceable as its built into the AC compressor, these may be bought on Ebay from £350 upwards but then would require degassing, fitting and then regassing so I would imagine it would be northwards of £800 to complete.  Speculation on my part.

 

To put the Flow Control sensor back into Operational Parameters we inserted a small LM741 amp inline to the sensor, basically this increased my Standby voltage on the sensor and then once the AC button was depressed the Magnetic clutch engaged and wheeee, chilly air onc more!

 

Intrigued?  There is a long version now!

 

Long Version

 

After having Kwik Fit regass my car a number of times to no avail i went to a garage for their help to diagnose my AC problem.  Once there I discovered Techstream as the tech was using it for diagnosing my problem and after some fiddling he was able to activate the Magnetic Clutch through Techstream.  This suggested that the AC could work but something was preventing it, his guess was that it was a pressure sensor as it would not come out very cold once forced.

 

He gave me a contact who he believed could help but unfortunately that contact never responded to me.  All the other local specialists either did not work weekends or had long waiting lists so, inspired by his work with Techsteam I thought that I could give that a go! I’m no spanner monkey but im a tech-bunny so, untimidated I went about locating Techstream and sourcing a lead etc.

 

Once I had these I had also been given a contact that I could obtain the official IQ workshop manual book from too so I contacted that person who kindly helped.  That person, Tarquin, or Mr P for short, was oddly enthusiastic about helping and got quite involved in my Techstream investigations and became a great source of help, motivation and nerdiness!

 

Initially I was having problems installing Techstream as it did not like going on a 64b Windows but we got over that (I use Techstream within a 32b Win XP VM (Virtual Machine) on my 64b Win 10 laptop, all funky and good!). Mr P and I were then able to compare readings of my faulty AC and his working AC, trying to spot patterns and compare measurements.

 

The On-board diagnostics reported code 79, Techtream B1479, this code indicated;

 

Flow Control Sensor

Wiring loom fault

AC Amplifier fault

 

Mr P allowed me to use his IQs cabin control panel as a test - I had same result with no AC.

I bought a replacement AC Amp off ebay for £14 – ****** sent me something that wasn’t an AC Amp, the case says ABS but I don’t know what it is.  Seems many people have this item listed as an AC amp but is wrong!

I bought a used AC Amp from a reclamation site after directing the guy to its location in the car cabin (behind the cigeratte lighter), £70 – Others are calling it an AC ECU – same result, no AC

 

Frustrating huh?! This was suggesting that the hardest thing to fix was the most likely fault but it would be an expensive gamble.

 

The Toyota manual advises for a diagnosis that in Techstream one should see the voltage for the Flow Control Sensor be above 0.7v (otherwise it’s Fault A) and below 5v (otherwise its Fault B) unless it remains fixed (ie, doesn’t change at all) which would be Fault C.  Mine was reporting 3.65v and would remain Fixed unless I forced Magnetic Clutch (where it would then drop to a little above 2.5v – 3v.  This suggested the Flow Sensor WAS reading the data.

 

Mr P then tested his and his results were 4.1v and when AC active it would bounce around 3.5v.

 

His displayed a similar variance range as mine although his started higher, but we were both within the Tolerance that Toyota mentioned.

 

I was pretty vexed by now as getting obsessed with this and im no mechanic, researching and learning how this all worked was distracting me loads!  I then contacted one of the original garages again and got a date for their guy to have a look.  I was kinda relieved that I could pass this on to someone so I could stop thinking on this however, the garage day came and went and all he could advise me was that the pressure sensor appeared ok and that he had a code, B1479 but that he didn’t know what it was.  I was back to square 1!

 

He asked me to take it back another week when he had researched the code but I felt this was going to go nowhere further yet so I got home and thought on this as something had to be wrong and we had a lot of data.  I then stumbled across a Lexus website where someone mentioned that their Flow Sensor v was low which prevented his magnetic clutch from engaging and that he boosted his to just over 4v using a LM741 amp.

 

I read the whole article and the various reports from others matched my fault profile IF I discounted that both Mr P and my results were within Toyota norms.  What if Mr Ps was woring BECAUSE he was over 4v and I was at 3.65v, a little under 4v?  Again, im no electrician either, my job is networking and IT yet, with bizarre co-incidence, my fellow Nerd in crime in this endeavour was Mr P, an electronics whizz!  We discussed the posts and amps, he was happy to build one and slap it into my spare AC Amp as a test, a bit like this;

 

 

 

In the real world it looks like this;

 

 

 

It is soldered onto the pins on the input/output from the Flow sensor loom into the AC Amp.

 

This boosts my current voltage up to circa 4v.  I popped my spare modded AC Amp it into my car Weds lunchtime (only takes a couple of mins) and started the engine before tentatively depressing the AC button and waited…clunk….the magnetic clutch engaged!

 

Cool air came out the AC vents and the compressor was whirring away as it used to! It was not freezing, but that may be that its not my original AC Amp or perhaps the pressure is not correct as it was not regassed with a working compressor so I need to sort that out.

 

The fault had been because my Flow Sensor whilst was within Tolerance, was presumably not hitting an operational voltage requirement (again, presumably set somewhere above 3.68v where mine wasn’t working but below 3.96v where mine now is working.

 

So, hopefully someone with an AC Magnetic Clutch not kicking in will be able to use Techstream to identify their Flow Control Sensor Voltage and ensure that the voltage varies when Magnetic Clutch is forced on to see if it would be a candidate for this fix.

 

I have attached 3 screens of my voltages, I hope they help. 

 

Thanks for all the help and advice, its been a great challenge to work through this which I would not have been able to doo without all your help and especially Mr P, Tarquin.  Wow, what a gem he is for the forum, a very proud IQ owner!

 

Ta

 

Nat

AC working - Active - Engine on.JPG

AC working - Inactive - Engine on.JPG

AC working - Inactive.JPG

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Wow, I am impressed with your determination. I think I would have given up as modern electrics are a bit like magic to me. I was ok with older cars before all this Can-bus and ECU's came in.

Glad you have got it sorted.

And yes I agree Tarquin is a very helpful gent. (When he changes his car, I think I'll follow him :laugh:)

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Good job it's fixed. Flow sensor is listed in bulletins for AC not working.

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Bizzarly only a short time after we fixed Bug's A/C, mine failed but not the same fault. Symptom was that when the A/C button was pressed, the A/C clutch engaged or seemed to and was visually spinning with the pulley. On inspection with A/C gauges there was 50psi on the low side and 50psi on the high side suggesting no compression. At tis pont i had it re-gassed by Toyota whi say they vac'ed out 60gms and pit in 380gms. They offered me back my car having cleaned it first and parked it outside the showroom. When i got in it the A/C was off. Upon trying it, it didnt work!  Now they must have know it wasn't going to work because on gassing it there was no high output. They obviously thought it was ok having realised no high pressure to just give it back to me without mentioning it and send me on my merry way. I pointed it out to them and in a flash tbey already has prepaired answer " oh well must be the compressor then" " £1800 for that to be replaced". So rather than stop the vac'ing when they discovered no high pressure they carried on so they could make £59 out of me. 

I did some investigation of the compressor and noticed that there was what looked like black sticky stuff on the side of the magnetic clutch and reaching down to remove it, it felt like thick Tar. After getting a very good understanding of the conditions needed for the compressor to operate, i concluded there was something wrong with the magnetid clutch. I measured tbe resistance of the coil and the12v energising it and all seemed with-in spec. I decided to buy a replacement clutch. After checking the part numbers i exhausted all attemps to find one. I found a few used iQ compresdors on Ebay and had resigned myself to buying one. I checked with toyota who quoted me nearly £400 for the clutch only and over £800 for the complete compressor. That price therefore implys £1000 !!!  labour for install. I found on ebay an Oil specialist company that sold Denso compresdors. And mine straight frim Densi in tbe west country £315 inc delivery. Just how much does Toyota want to make in profit?  To day i set about the task of swapping the magnetic clutch frim tbe new compressor to my original one. Even with the front wheel off and a plastic instpection panel removed its difficult to get grips in there and a torque spanner but it was achieved within the hour and no need to disturb the fan belt or refrigerant. Note if you attempt this, there is up to 3 washers that set the gap between the clutch plate and pulley. The iQ only used 1.  On having access to the clutch it was obvious thsat the rubber material had all but perished  and although it looked like the clutch was spinning when engsged to the pulley, the middle connected to the compressor was stationary. After it was replaced it now works perfect again. Reason for failure, the car has done 125,000 miles with the A/C all tbe time

David 

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Good to know for future reference ;)

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Hi there, i’m new here and by reading the following conversation above i clearly understood that i have a similar issue with my IQ. Fistly, the issue was the cooling aspect of the a/c since one day just stopped to cooling but the fans and heating were working.Then i have proceeded in an appointment with a garage.At first they told me that when you press the button for A/C  it doesn’t send signal to the compressor to spin.After two days of trials in suspected issues they didn’t reach into a conclusion so i decided to take it to toyota.But then i realised that they did something wrong and mess up the display panel.Sometimes it works for a some time and then goes dead.So apart the issue of cooling,now i have the issue with the display panel.Toyota thinks that about the display panel the issue it is the A/c amplifier. Any thoughts or recommendations?

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Hi there. I do need your help which i do believe will save me for a mass amount of money. My air con amp has issues and does not allow to the air condition to work properly. I spoke with toyota and to replace the existing one with a new one will cost me around 500 euros. I saw many used amps in the ebay but not with the same code with mine. so my question is whether another amplifier matching mine without having the same code. My IQ has a date of 01/09 automatic and the amplifier code is 88650-74030.Thank you!

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Hi Lambous

Apologies, i have a palava logging into this site everytime and have to reset the password which is nuts complex for a forum that you can read without logging in anyway.

As for the A/C, how may i help? 

Has anyone connected a laptop to your IQ to see what errors are in the log? have you tried running a diagnostic off of the A/C control panel by depressing the buttons when activating the ignition? (full instructions are in the thread above)

What code do you get on either the laptop or A/C panel?

With a laptop attached, can you start the A/C via the Magnetic Clutch test?  If it starts you will hear the engine rev higher and cooler air, this would be a good indication of the mechanics being ok and probably a sensor fault.

If its mechanical then probably would need a new compressor, Dave fitted his own replacement as unfortunately he experienced a fault shortly after we got mine working by modifying the Amp signal.

If its sensor then you may be able to clean it, i think later Dave even found somewhere that the sensor was available from (I can look in my emails/sms if necc)

I may have a spare Amp with that number, i bought a replacement as part of my diagnostics.  How much are you looking at?  i do keep meaning to sell it but forget.

I will look Friday as its in the car and a bit early at mo.  I'll say which mine is (The spare one)

 

Ta

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Thanks for the reply Bug.Basically as i ve send Dave my situation has this way: I had a faulty AMP preventing the control panel to work properly(working for 2-3 min and then blank). Anyway i ve change the amp with the same code and problem fixed.However through the faulty amp the compressor is kicking when you press AC but with the new one does not.Maybe the new amp needs programming?It is a strange situation since The 2 amps are exactly the same with the same codes.Anyway i will go now to the garage to see what the technician has to say and keep you updated.Also if you have any clue what it might be the issue,feel free to come back to me.(sorry for my English language however it is not my first language)

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Hi Lambous

what does the onboard diagnostic report on the Control Panel? To access this you Hold Auto and Recirculate whilst initiating Ignition

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Hi all, figured this is the best place to ask is in this topic. Hope someone will answer 

 

I have an auto HVAC (no knobs, but the display one) 

It just died. No life in the display - and so there is no life in the buttons. Whatever I push, it just does not turn on. 

I checked the fuses you guys were talking about, the 7,5A ones and the 30A one, all good. 

Is this a known problem? Didn't find anything similar,

 

The car is 2010, 1kr-fe, manual. 
 

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Hi Bug / Tarquin,

I'm experiencing the same problem as you did Bug, with fault code 79. The description of your solution is brilliant - thanks for documenting.

Do you have any photos and/or wiring diagrams of the fix you did adding the amp to the air con control unit. And any instructions to access the control unit?

All help would be gratefully received.

Chris

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Hi Bug

I have an IQ (2009) and it seems to have an AC problem exactly as you described.

did you get yours fixed? What was the problem?

Kim

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Hi

Please accept my apologies, i have been unable to access the site for some time and, well, gave up on it to be honest as my iPhone required me to set a new password every time i came to the site and the password requirements are so bonkers.

Anyway, i am here at the moment, do you still need help?

Thank you

Natalie

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Hi

I have been working with Dart driver on this problem with her IQ and offered the following to her however, she has currently declined.

I still have my spare A/C ECU that i bought way back when Solley and I were originally working on this problem.  At that time i had ordered a number of parts that were supposed to be the AC ECU Amp and i think it was 3rd or 4th item that i received was which really was the AC Amp.

I have been somewhat tardy in doing anything with it since we resolved this problem so, if anyone would like it then please do contact me. I shall put it on eBay in due course but would of course rather help someone if i can given how messy it was to receive this in the first place.

To be clear, it is the AC Amp that we originally used to trial the prototype fix without risking my original Amp.  Once we confirmed the fix worked and my own Amp wasnt at risk i removed it and the wonderful Solley attached an enhanced version of the prototype to my amp and then we reinstalled it.

This spare amp is therefore without any modifications as each "fix" will require the Volages of your flow sensor, these can be obtained by using Techstream in your car.  It is not possible to 'pre-fix' the modification as if the boost makes the voltage too high or too low then the A/C Clutch will not engage, there is a very small window for the voltage to be acceptable.

Using this spare amp can save you from Breakers or eBay costs of £15 to £175 and not necessarily receiving the right item.  It also allows you to test without damaging your own Amp and you could pass this back on once you are finished with it.

Toodlepip!

 

Nat

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So what would the indicative cost of the spare amp be, and, if there is a cost, should it note be in the For Sale section.

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Hi Frosty

Sorry, price would help wouldn’t it, useless!

I am only interested in what i paid for it, £70.

The steps one needs to do are broadly;

1 - Obtain access to TechStream
2 - From TechStream record the FlowSensor Voltage
3 - Calculate the voltage difference between Actual (above) and Required (from this forum thread)
4 - Modify ECU to boost FlowSensor signal to Required Voltage (above step informs electrician on modification requirements, forum post informs which 3 pins the modification is soldered to)
5 - Place modified ECU in vehicle (removing existing as appropriate) forum post for details
6 - Test
7 - live happily ever after (well, try!)

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On 6/26/2019 at 9:48 PM, Bug said:

Hi Frosty

Sorry, price would help wouldn’t it, useless!

I am only interested in what i paid for it, £70.

The steps one needs to do are broadly;

1 - Obtain access to TechStream
2 - From TechStream record the FlowSensor Voltage
3 - Calculate the voltage difference between Actual (above) and Required (from this forum thread)
4 - Modify ECU to boost FlowSensor signal to Required Voltage (above step informs electrician on modification requirements, forum post informs which 3 pins the modification is soldered to)
5 - Place modified ECU in vehicle (removing existing as appropriate) forum post for details
6 - Test
7 - live happily ever after (well, try!)

Do you still have this? 

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