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.
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.
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!
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!