Climate Control Working But Panel Flashing - What Error 65535 Really M

[seatkid]

As I explained elsewhere, I got my car back from the VW dealer (Hayseldens of Doncaster) where they changed the water pump and thermostat, with some additional bonus extras – bent sills and a cc unit with a flashing panel that wasn’t there before.

 

Panel flashing on a climate control unit for 15 secs or so after starting the car, indicates that the unit detected an error of some sort. In 90% of cases, this is due to low refrigerant gas level in the system, triggered by a 3-way (too high, OK, too low) pressure switch, which on my 98 Tdi is mounted on the receiver dryer. The unit doesn’t engage the compressor clutch, so no cold air is also an accompanying symptom.

 

In my case, however, the clutch was still pulling in, and I still had cold air. So low gas was not the problem.

 

As it became clear that Hayselden were not interested in my problem (that they seemed to have caused) – I decided to splash out £7.98 on a Fleabay VAGCOM lead. It arrived the next day, so I installed the accompanying clunky drivers and software (VAGGOM 409.1 and VCDS lite) onto my clunky, war torn, just about held together with a roll and a half of duck tape 1998 museum model laptop, under Windows ME. Not expecting much joy, it installed ok so I plugged it all into the car, and after some pregnant pauses – it all seemed to communicate OK with my car.

 

First I scanned the AutoHVAC controller and got

 

1 Fault Found:

65535 - Internal Control Module Memory Error

00-00 - -

 

Hmm, strange, I thought (with my electronics designer/programmers hat on)

 

I pushed the Clear Faults button and it came back no errors found. Great! (or so I thought). Removed the lead – turned the car on, no flashing screen, J and drove to the shops to pick up the wife. After loading the car, started the car and the CC panel started flashing again. Shit. Anyway to cut a long story short, although I could clear the error it kept coming back.

 

Step 2. Scan something else with VAGCOM – found an error in another controller – I think it was the Cent. Elec Controller – something like int.monitoring sensor fault. So I cleared that – and that did go away and not come back. But didnt help with the CC fault which kept reporting 65535 - Internal Control Module Memory Error.

 

So I started googling and soon it became pretty clear this is a relatively common reported fault (on all controllers) and the opinion of most, including dealer techies etc. was that this was an internal memory corruption error, it can’t be reset, the module is f**ked and you need to change it for a new module, or alternatively just live with it.

 

Ross-Tech (the VAGCOM people) list something similar

 

Possible Causes

• Wiring from/to Control Module faulty
  
  • Voltage Supply and/or Ground Supply faulty
    

  [*]Control Module faulty

  [*]Control Module Housing leaky

Possible Solutions

• Check/Clean Wiring from/to Control Module
  
  • Check Voltage Supply and Ground Supply including the Main Supply/Connections at the Battery
    

  [*]Replace Control Module

As a hardware/software/firmware engineer of yesteryear, I found it hard to think that the module could just corrupt its firmware, even if the dealer was clumsy with the battery connections. Digging around and looking around the engine bay (around compressor/water pump/themostat) and external sensors (temperature sensor next to nearside foglight) there was nothing there that didn’t work or could be associated.

 

I nearly just gave up.

 

Then I came across an obscure post on a german forum, and it was saying that someone had this problem, took his cc unit to bits and found the little fan that sucks in the air next to the LCD wasn’t turning – it was made up with dust and stuff. After cleaning it out it started spinning and his flashing LCD went away.

 

So, being the lazy type, and not wanting to strip down the dash, first I listened close up to the tiny vent next to the LCD, when turning on the ignition. There was a squeeling hissy, not very healthy type noise which cut out after several seconds.

 

So out with the vac, soft brush etc. I basically attempted a clean up though the vents. Brushing, sucking etc. Checking several times – the noise and switch off hadn’t changed. I persisted for some time, also adding the odd poke and banging in the way you used to fix those old 1960’s televisions. When, all of a sudden, I heard a little whirring noise – not unlike a mini version of the aux heater winding up coming from the vent. Next time I switched the ignition, the CC unit had stopped flashing.

 

Cutting the story short.

 

Fault 65535 – Internal Memory Module Error

 

Should rather say

 

Fault 65535 – Internal Module Fault – unspecified (the firmware guy was too lazy to finish the code off properly)

 

So for all you 10 percenters who have this fault on your CC unit – a flashing panel, but the compressor still working and giving cold air, it may very well be the internal fan on the CC unit is blocked with dust.

 

THis 65535 error probably applies to other controllers. e.g. early Tdi ECU have the MAP sensor built into the unit, when the rubber pipe in the unit gets gunged up, spilts or collapses, this generic 65535 error code pops up.

 

So if anyone, particularly your dealer, says the module is f**ked and you need a new one at £895+Vat - just say error 65535 Internal bullshit error - walk away.

 

Sorry for the long story.

[chrispb123456]

Well done mate that's one for the record book, have thought that vent should be fitted with a proper filter, always give mine a wipe over now and again but there must be some that gets through unoticed :45:

[gregers]

:45: :) :46:

exelent post m8,

 

 

nik this needs to be added to faqs m8.

[Saif Rehman]

_{Absolutely brilliant and well done!}

[popuppirate]

have a similar problem but i have cold air and my ambient temp fans are working but my panel still flashes for 15 secs,according to my kts 650 its to do with the recirculation flap motor not working, anyone heard or this before ?

[alan_131]

popuppirate - does this sound like yours...http://www.fordgalaxy.org.uk/ford/index.php?/topic/20737-recirculated-air-flap/

 

seatkid - great writeup. don't know how I missed it before. Agree about the firmware, really annoying when the module's monitoring has clearly identified a fault but won't tell you what it is. I suppose this follows the module level replacement principle, but why they can't flag the real fault and have the dealer system say the preferred fix is "replace module" I don't know. If I'd written / spec'd code like that I'd be ashamed but VW no doubt have their very commercial reasons.

 

Just a thought, but some laptop repair guides warn of damage to circuit boards caused by static spikes created by the airflow using a vac. on cooling fans. Not sure this is so and feel the damage(if it really does happen) is more probably down to an excess voltage generated by the spinning (much faster than when it's normally driven) fan. I'm wondering if this is a possibility here; guess not if it just runs connected to the battery, but if it's driven via an IC that current monitors for error detection.... Nowadays I either take care to keep the fan speed slow, or stick something like a cocktail stick through the blades. I'm not an engineer just an old computer bod, so be very interested to hear what you think.