resistors ????

[djwrays]

[Edit: Kaz-kzukNA1 25/Aug/22 16:15 This post - #1, was originally posted in the 'NSXCBWebsite discussion' forum.
Thus, merged to this thread as it's duplicate of almost the same contents.
Also, moved to the 'Technical' forum as well. ]

Hi All.

Please help.
Im probably on old ground here but once again back from South Africa, got the old bus out ( 95 targa) and the heater fan is playing up again.
Only works on full auto or full speed fan.
By memory its the resistors and not really a dealer repair.
im based in hertfordshire.
could anyone take on the repair for me.?

Thanks Guys.

[djwrays]

Hi All

Maybe treading on old ground here but having the same old blower fan issues on my 95 manual.
returned from Africa and it only works on full chat.

Very frustrating.
Am told its the resistors but its way over my head,
Any one local ( Hertfordshire) who could possibly take a look ??????

Thanks Guys

[Old guy]

Definitely not local to you; but, I may be able to help a little.

The part that might be in question is not a resistor. It is a power transistor that is used to apply pulse width modulation to the blower motor to reduce the blower speed. The transistor is by-passed by a relay at max speed which is why the fan will work on high speed with a failed transistor.

The transistor is mounted in the actual blower housing because it needs forced cooling air flow. It is moderately easy to access from the front compartment after removal of the spare tire and battery. The part # is 79340 SL0 A01.

1991-2005 Acura NSX Transistor Assembly 79340-SL0-A01 | Acura Parts World (https://www.acurapartsworld.com/oem-parts/acura-transistor-assembly-79340sl0a01)

There are aftermarket versions available for a slightly lower cost

More Information for STANDARD MOTOR PRODUCTS RU74 (rockauto.com) (https://www.rockauto.com/en/moreinfo.php?pk=444126&cc=1000887&pt=6557&jsn=347)

As you can see, even the aftermarket piece is rather expensive for what it is. If you are up for an experiment, the actual power transistor inside the module is rather cheap. The original transistor is a Toshiba 2SD 1460. It is out of production; but, they still seem to be available from surplus vendors for $10 - $15. However, there are cross reference lists that will give you a currently in production replacement. On the original module, the power transistor is potted and you have to mechanically dig out all that potting compound to get at the transistor which can be a bit of an adventure.

The blower power transistor tends to be dumb-ass reliable. Since OEM or aftermarket replacements are pricey, make sure that it is your blower transistor that has failed and not the climate control unit. As a first step, run the CCU diagnostics (described in the owner's manual and the service manual) to make sure that there is nothing obviously wrong with your CCU. If there is a problem in the PWM control circuit in the CCU this could kill speed control with a perfectly fine blower power transistor. The CCU diagnostics may not pick up all the PWM circuit problems; but, its a place to start.

If blower speed control worked before you left for Africa and no longer works after your return I am more inclined to think that it is a CCU or wiring problem. Power transistors tend to fail in service from over heating, not just sitting around. The incidence of CCU problems due to leaking capacitors is much much higher than the incidence of power transistor failure. Give members Kaz or Heineken a PM and they may be able to help you with a CCU problem

[duncan]

Hi,
The symptoms you describe are more commonly caused by internal components (capacitors) in the Climate Control Unit (CCU) failing. These are components that on manufacture are sold with an expected hourly/temperature life.
If this the reason,
- the CCU will need to removed, opened up and examined for damage. There are a range of threads here, see the blogs section of this site with posts by Kaz and Heineken, on Prime and Prime’s Wiki section and some on YouTube showing the removal process.
If corrosion damage from failing capacitor(s) is visible then, as discrete components, they can be replaced.
In no particular order the follow people have/ can undertake the necessary repairs and all can be recommended
- in the UK, Kaz (see his blogs here)
- in Europe, Heineken (ditto)
- in the US, Briank (see Prime) and
- in the US, Science of Speed

[Kaz-kzukNA1]

Thank you for the reference, duncan.


Hi, djwrays.
With 95 model, if the A/C CCU was never serviced before, there is no chance of surviving without the leaky capacitor issue.

Many won't notice it until something goes wrong.

One of the most typical failure mode is the blower fan only operates when set at max speed setting.

Lots of examples here; http://www.nsxcb.co.uk/blog.php?1811&blogcategoryid=24

Photo based A/C CCU removal procedure here; http://www.nsxcb.co.uk/showthread.php?15552-How-to-remove-centre-console

Seemed to be your NSX is in UK so if interested, please contact me through this email address as displayed in the blog section;

kaznsxcb-002 [at] yahoo [dot] co [dot] jp
(one word, no space, please replace the [ ] section with @ and . )

Please note the domain ends with jp and not uk.

This email address is virtual one for spam protection and disposable.

Once you have contacted, you will hear from me from different email address.


Kaz