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Old 22-06-2006, 06:17 AM   #1
Peter
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Default Heater Channel Replacement - How & Why

There have been a number of heater channel replacement queries recently but my "body off" and "no braces" seem to be making little impression. This may be because I usually respond to queries and my message may be getting lost in the confusion. So, I thought it might be better to lay out a more complete view of this procedure in the hope that it may make some sense and be of help to anyone who might wish to read on. It is still a fairly general account so I will clarify or expand wherever asked to do so.

First of all, I would like to state that I realise that there are a variety of 'local' limitations that will dictate how this job can actually be done. However, these "limitations" do not alter the fact that there is a proper way to do this and, if the correct procedure can be understood, it will assist and improve the quality of the job irrespective of the actual methods employed.

I have always advocated taking the body off and the general reasons why are:

1. You need to replace the seal.
2. You can't properly remove or fit the channels with the body on, without employing some improper methods - Like flexing or trimming panels.
3. More space to work and less frustration makes a better job

There is far too much concern over lining up the heater channel with the chassis bolt holes; this is not of primary importance. The main concern should be the door aperture (not the chassis bolts). If you get this part wrong, there is little you can do other than cut of the heater channel and start again. Not only do you have to obtain the correct gap between the A & B-pillars but you have to maintain the correct height and lateral positions. Remember that the outside face of the channel is also the 'seal joint' for the door and so must line up properly with the corresponding seal flanges on the A & B-pillars.

It is not necessary to weld everything together so that the door opens and shuts perfectly. Just as long as the dimensions are correct, the door can be made to fit later. At the factory, although the shell components were placed in a jig to get the correct shape for the door, it was impossible to actually maintain that shape once the jig was released. Invariably, what resulted was a slightly parallelogram door opening for a 'square' door. The shell was then 'jacked' one way and then another to 'make' it fit the door. Luckily, most of these procedures are not required when replacing the heater channels as the rest of the body has been 'shaped' at the factory so most, if not all, of the alignments will fall into place.

Don't use the Door as an alignment tool. It will just get in the way and add leverage to the A-pillar and, in the end, it won't do any better than a measuring tape.

Now the one that really seems to upset people is: Do not use braces to achieve or protect the correct body alignments. This may sound crazy but it is a practice that seems to have been brought about by either fear and/or the lack of understanding of how the bodyshell works. Remember that the body has already been assembled correctly at the factory, so it is not a case that removing one connecting panel will somehow cause the shell to reduce to a lump of unaligned jelly. The other thing to remember is that the body gets twisted and damaged throughout its life and this can affect the door alignments. If you then brace it all up, what you have done is simply fix in all those 'errors' and thrown away the chance to put it all back to original. Even if the body alignments are perfect, the actual installation of the braces can cause a distortion. As I have stated on numerous occasions, only brace the A & B-pillars if you think that channel may completely detach itself from one or the other pillar, while lifting the body off the chassis. Once it is set down on its working supports, remove the brace(s).

I hear people explain how you have to cross-brace (A-A etc) to maintain the correct dimensions, but this is entirely unnecessary. If your new heater channels are so badly made that they do not have the correct shape, then braces won't help you. The front section of the body is rigid all by itself, right down to the A-pillars (it was a subassembly at the factory) so they won't move against each other, The rear section too, is fairly rigid. All that is left to worry about is the alignment of the front section to the rear section. This is completely taken care of by the setting of the lower door gap (950-951mm) when you fit the heater channels. If after this the front is not straight with the back, then there is accident damage that has not been fully repaired. Either way, you have no choice but to set the doors gaps properly and there is nothing more that you can do that will make any difference.

All bar one of the heater channels available today are aftermarket and generally of low quality, the only genuine channel is made at VW Mexico, for the 69 and later models, and is probably the best ever produced. As with the VW Mexico product, heater channels should be supplied in two pieces; the upper part (which contains all the heater ducting etc) and the lower bottom plate. This makes it possible to fit the upper section according to the needs of the bodyshell and door aperture, without much concern for the alignments with the chassis. The bottom plate can then be fitted to ensure that match with the chassis. When heater channels are supplied as a complete unit, you can't be sure that the bolt holes will match. If you fit the channels so that the holes do align, then you may then have to compromise the fit along the door opening, rear quarter etc; it can be a difficult enough job without putting major obstacles in your way, too!

Once you have the complete channels fitted and before you reinstall the shell on the chassis, you can refit the doors. Chances are that they will not fit, so you then have to go through the door alignment procedures (another long winded topic). However, as long as you have fitted the channels so that the 950 to 951mm door gap exists, you will be able to get the doors to fit, just like new.

Like I said, a relatively brief account, but a start!
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Old 22-06-2006, 08:19 AM   #2
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sound advice mate,
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and it's got a spare engine in the boot..
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Old 22-06-2006, 09:46 AM   #3
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Pete i did use your method of checking the door aperture measurements as well as checking the door opened and shut in the opening. I had no option but to brace the front section as the car had listed enough to warrant this action. As a carpenter by trade i'm well aware of structure and stability and all things safety. I regard the info you have given me as valuable along with all the input from the other guys. I've done welding on cars to every other panel apart from heater channels and although i had an idea what could be done i was just curious as to what the other guys were doing. Thanks for everything it's all good stuff
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Old 22-06-2006, 09:56 AM   #4
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Good guide, thanks.
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Old 22-06-2006, 10:01 AM   #5
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Good article and interesting reading. Just a quick clarification though.

The following bit:
Quote:
Originally Posted by Peter

Once you have the complete channels fitted and before you reinstall the shell on the chassis, you can refit the doors. Chances are that they will not fit, so you then have to go through the door alignment procedures (another long winded topic).
The door alignment procedure sounds like a real git of a job, so if the door fitted before the channels where replaced, then the body braced,, doors removed, channesl replaced, then surely the doors would just fit fine again afterwards and you wouldn't have to jig the doors around?

Or have I completely misunderstood?

I plan on doing the heater channels on my bug for the first time later in the year so any info is a bonus.
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Old 22-06-2006, 10:10 AM   #6
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[QUOTE=maddave2000]so if the door fitted before the channels where replaced, then the body braced,, doors removed, channesl replaced, then surely the doors would just fit fine again and you



My thoughts entirely, seems to make sense so this is the way forward for me on this occasion
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Old 22-06-2006, 11:08 AM   #7
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Good advice Peter, although my chosen method is to tack the channel in before i lift the shell off to help keep some strength in and avoid chances of distorting the shell. After all, its inherent torsional rigidity isn't there is the channels are missing!

Having successfully kinked a roof panel in the past by underestimating how rotten the heater channels were before we lifted the shell off, i'll stick to belt and braces!

Do you lift you shells off with 2 scaffold poles running fore-aft through the front & rear screens or by jacking the shell and rolling the pan out?
I'd be interested to know which method you think is best.
I find jacking works well as i can get the shell about 4" up in the air and supported on planks and then pull the pan out by taking the wheels off and sliding it back.
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Old 22-06-2006, 11:51 AM   #8
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Quote:
Originally Posted by maddave2000
....if the door fitted before the channels where replaced, then the body braced, doors removed, channesl replaced, then surely the doors would just fit fine again afterwards and you wouldn't have to jig the doors around?.....
You would think this would be the case but, in practice, it doesn't always turn out that way. It doesn't take much for the door to mis-align and after all the welding etc, when you remove the braces, the shell can spring, very slightly, into another position.

I would like to stress that braces are not, in themselves, wrong to use, but they are inherently incorrect. It depends on how you weld them in, which piece goes in first, whether the door aperture was correct in the first place etc, etc. If you are able to follow the correct procedure, then braces simply become unnecessary and by not using them, you avoid any of the possible side-effects. Once you rely on braces, you are stuck with them and have no room to manoeuvre.

Another point here is that sometimes the reason a door does not fit, prior to replacing the heater channel, can be mis-understood. The repairer may assume that a sagging door (for example) can be corrected by repairing the lower A-pillar or jacking the door when welding the channel in place. However the problem might have been the upper hinge area on the A-pillar and now an additional error will have been built in. Irrespective of how the door hangs, as long as the dimensions of the opening are correct, that is all you need. The A-pillar hinge plates can be twisted, afterwards to align the door in particular ways. In more extreme cases, hydraulic jacks may have to be used to 'square' the door opening, but none of these methods change the actual linear dimensions of the door opening.
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Old 22-06-2006, 12:13 PM   #9
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Quote:
Originally Posted by Raph
....my chosen method is to tack the channel in before i lift the shell off to help keep some strength in and avoid chances of distorting the shell.....Having successfully kinked a roof panel in the past by underestimating how rotten the heater channels were before we lifted the shell off...
This is why I advise the use of braces when the condition of the heater channels is so bad that they cannot be relied upon when removing the shell. I think it would be easier to temporarily fit braces, in these cases, than prefit the new heater channels.

Quote:
...Do you lift you shells off with 2 scaffold poles running fore-aft through the front & rear screens or by jacking the shell and rolling the pan out?...
You can use the front/rear screen method, but I prefer to have the windows in before I put the shell back on, so I wouldn't take them out, just for this job. If you remove the engine first, then you don't have to lift the shell so high. Then you can use short lengths of 2x2 under the the fuel tank opening and below the engine bay. I used two free standing cranes (one at the front and the other at the rear), and I would not even have to remove the lids. Once the shell was up, I would turn one crane so the chassis could be rolled away. I also used special lifting brackets that could be bolted to the bumper mounts, though this method is best used when all the welding has been done, or in the case where you know the bumper mounts are secure.
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Old 22-06-2006, 12:19 PM   #10
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Quote:
Originally Posted by Peter
I also used special lifting brackets that could be bolted to the bumper mounts, though this method is best used when all the welding has been done, or in the case where you know the bumper mounts are secure.
That's a brilliant idea, i'll freely admit i hadn't thought of that.

Where under the fuel tank do you put your bit of 2x2?
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