Aux Heater Memory Error

[chromedome]

I keep getting a fault code 65535 telling be I have a memory error. Once cleared the aux heater starts up straight away.

 

You can switch off the ignition for a few minutes and the fault does not come back, however, leave it a few hours and up it pops.

 

I have read that this may be a power supply issue so could it be my battery because it is getting a bit tired starting first thing in the morning?

 

Thanks.

[seatkid]

Do you have climate control?

 

The 65535 code is a general fault code that the ECU does not have any further details on. It is not a "memory" fault as in checksum or whatever - its a "something has reported a fault, but not with a fault code"

 

In my case it appeared when the small fan in the cc unit that draws air in (this is a MK1 btw) - presumably to measure internal temperature - was seized (due to muck and fluff). After much poking and faffing about with a vacuum cleaner hose, etc it eventually freed up - I could hear it spin up quietly when the ignition was turned on. The 65535 error disappeared as did the flashing digits on the CC unit.

[acecard]

I thought this number rang a bell from my computer programming days - so I attach a bit of info - it sort of confirms that this code is non specific but the highest it can report - don't suppose it helps much except it apppears when it don't know what else to report B)

 

"65535 is a frequently occurring number in the field of computing because it is the highest number which can be represented by an unsigned 16 bit binary number. Some computer programming environments may have pre-defined constant values representing 65535, with names like "MAX_UNSIGNED_SHORT". In older computers with processors operating with a 16-bit address bus (such as the MOS Technology 6502 and the Zilog Z80), 65535 was the highest addressable memory location."

[chromedome]

Seatkid it looks like you are spot on. I went out and poked around with a long bristled paint brush followed by the Dyson. Put my ear to the unit and heard it whirring away so went out for a ride to pick my son up from work and viola.

 

I must ask.........................how on earth did you discover that this may be a problem? If I went to Frauds it would have been "£500 mate for a new booster".

 

I seems I had two problems. First the secondary water pump was knackered and this one. Am I right in saying that the climate control panel only uses the left hand vent as you look at it? This one has been getting fluffed up recently.

 

Thanks again for your valued information, you are a star.

 

Unlike some I like to publish my success/thanks for others to use. More often than not you never here any feedback.

[chromedome]

Acecard, why put computers in cars. :glare: . Bring back plugs, points and carbureters (what some people say).

 

I am quite good with homes pc's but in the car arghhhhhhhhhhhhhhhhhhhh!!!!!.

 

Thanks for the input though.

 

A garage did read this code for me and said it was an ECU fault. :18:

[acecard]

Acecard, why put computers in cars. :glare: . Bring back plugs, points and carbureters (what some people say).

Totally agree - bad move for the people, nice one for unscrupulous garages

 

I was happy with plugs, points, feeler guages and spinning the dist cap to see how my mini would respond - sigh

[seatkid]

Its interesting to note that a clogged fan in the CC unit may very well stop the aux heater from firing up....

 

I must ask.........................how on earth did you discover that this may be a problem?

 

As a former firmware/software designer, 65535 (aka (short int) -1, aka 0xffff aka..... ) I immediately think "default value" or "undefined". I bought a £8 VAGCOM to fathom why my cc panel was flashing and yet the compressor/cooling was working. When this came up it was just a matter of time (and a bit of luck) before I tracked it down. I must admit I came across a German site describing the flashing LCD and showing them stripping the CC unit, finding the clogged up fan/cleaning it and so fixing the fault....

 

So, anyone with a 65535 memory error - DON'T change your ECU. Its simply an "unspecified error"....

 

On the mk1 the cc unit has one one vent to the left of the LCD display...and I expect all cc units get clogged up with time (as do fans in all computers)

 

A garage did read this code for me and said it was an ECU fault.

 

This is really the fault of an incorrect/ambiguous description from the diagnostics software supplier (with VAGCOM its Rosstech but they probably got the info from VW)

Edited February 13, 2013 by seatkid

[chromedome]

If I remove the CC Unit to clean it does it need to be reset by Frauds?

 

Has anybody got a link showing an exploded view of the unit.

 

After a fairly long idle period I have to tap the unit and mess about with the temperatures to make the booster heater start up. :huh:

 

Thanks again for the help so far.

[seatkid]

This may or may not help

 

http://www.passatworld.com/forums/68-b5-garage/342102-how-clean-your-climatronic-control-module.html

 

It doesnt look remotely like a Mk1 cc though....

[chromedome]

Thanks for the link, at least it shows me how to remove the CCU. The one shown is a bit different to the MK2 Galaxy but was interesting if that the gizmo behind the air intake looks to be a fan and sensor combined. Glad I didn't spray some WD40 in. I used an airline and Dyson alternatively and managed to get a little bit of fluff out. It would not take a lot of fluff to stop a fan of this size.

 

At least I now have toastie feet and have hopefully not got to get under the car in this weather.

 

This episode has been a real eye opener for me thanks to you two guys and hopefully it will help others who are having similar issues.

[chromedome]

A bit more of an update. I was still getting the occasional failure unless I fiddled with the climate control panel.

 

I bought some electrical contact cleaner, removed the connectors one at a time and sprayed the connectors with the cleaner. Early days but the aux heater does appear to start earlier and has not failed yet.

 

Car electronics will always amaze me.........................