www.jec.org.uk

Hi,

I am (very slowly) rebuilding a XJ12C whilst fitting some later components being taken from a XJ12 S3 donor vehicle of unknown provenance (don't know if everything was working). Therefore, I am either testing each item or replacing it on spec with a known working item. Having got to the blower motor units, I would wish to replace the transistor packs (just in case), but cannot find a copy of the JEC magazine article that gave a detailed description of how to replace the transistor or recommend a suitable replacement - my transistor is corroded and has no legible markings on it.

1. Does anybody have a PDF (or copy) of the step-by-step transistor replacement procedure?
2. Which transistor is a suitable replacement and where can I get one from?
3. Does anybody supply a 'new' replacement transistor pack (so that I don't need to get my soldering iron out)?

In addition, I note that within the blower mixer unit, that there is a Hella 4RA Relay mounted within ... should I replace this item on spec too? The relay looks in good condition, but it has been fitted and unused for nearly 15 years. A recommendation here for a reliable source for replacement relays would be useful - if this relay were to fail ... a huge job to get to it again.

Anyway, thanks in advance for your responses.

Kind Regards

Mr Souter
Westbury, Wilts, UK

I thought the series 3 had a Delanair II which is different, but if your transister system is the same as used on the XJ40 (and XJS) this link may help, I wrote it many years ago but it might be of some use.

http://www.jag-lovers.org/xj-s/book/acblower.htm

Hi, yes and thanks ... the transistor system shown in your link is exactly the same as the system fitted to my 1985 S3 Donor. I shall look at the content of your link in greater detail at the weekend, but at first glance, the information provided looks comprehensive and spot-on. TVM.
Regards
Wolfie Souter
Westbury, Wilts.

Thanks again, I have had a look at the detail within the link and the circuit diagram plus component list is extremely informative.

However, it is many years (nearly 40) since I have built a circuit from scratch ... anybody got a 123 set of instructions on how to layout and connect the components on the breadboard? At College, we were posh and used tracked breadboard, so adding wires to untracked increases the number of fiddly bits.

Thanks in advance

Wolfie Souter
Westbury, Wiltshire, UK

It isn't as bad as it looks really, the transister dictates four of the connections, the rest just connect around it. You may be able to use the original board which would simplify things.

It was over 17 years ago since I repaired mine and I'm pleased to say they still work correctly. The hardest part was removing and refitting the blowers.

Hi and 'yes', not as bad as it first looked.

However, all RS Part Numbers have been superseded but I can identify replacements - that is, all but the 0.01 micro Farad capacitor. Any specific spec for this capacitor? I will need to buy as a 10nF and spec from there - any specific rating or composition recommended?

Thanks again

Wolfie Souter
Westbury, Wiltshire, UK

I expect Maplins would have them, I'm no electronics wizzard so unfortunately I can't advise if a different specification would make a difference.

Okay, I have purchased all of the piece-part electrical components and am in the process of de-soldering and re-soldering in replacements - quite straight-forward now that I have purchased a de-soldering pump.

However, what I took to be an easy on-spec replacement of the Hella 4RA 003 510-34 12V Relay located inside the Blower Motor Air Box transpires not to be the case as I am unable to find a 'new' replacement in the UK. Does anybody have any suggestions or know if the Part Number has been superseded?

As this relay will be inaccessible once everything is refitted, I would like to fit a known working 'new' relay whilst I have access to it.

Hope that somebody can suggest a suitable replacement relay or source for two 'new' items. TVM.

Regards
Wolfie Souter
Westbury, Wiltshire