Hi,
I have a 2005 S-Type V6. My A/C is blowing hot all the time - switching from LO - HI A/C or adjusting temperature has no effect, just hot. The fault first occurred when I was sitting in the car. The A/C blew hot and I smelled a bad electrical burning smell. My guess is that the actuator motor burned out, possibly because the blend door got stuck(?).
I took it to the dealer to have the car hooked up to the IDS and they pulled B1265 "Cold Air Bypass Actuator Motor Drive Circuit Failure". I looked in the JTIS workshop manual and it appears that the actuator/motor is just behind the driver trim panel beneath the steering wheel column - and the removal/replacement looks fairly straightforward.
A few questions:
1) Does anyone know where to find this part (other than dealer) in Canada/US?
2) Is it possible that there is also damage to the CCM? I understand that when the DCCV issue happens, that can blow the CCM board requiring some soldering. Could that have happened here too?
3) Is there an easy way to test the actuator circuit to make sure that there is no further damage beyond the actuator?
4) If the blend door getting stuck is the ultimate root cause of the problem, what can i do to repair that?
5) Am I likely to vaguely be on the right track?

I suspect that if the actuator is the only problem, getting the dealer to address this won't be insanely expensive (unless the part is ridiculous). I'm more worried if the blend door itself is the issue... or they want to replace the CCM.

Any guidance would be really appreciated.
Thanks
Chris

 

Ignore the B1265 fault code. The stated bypass actuator was removed starting with VIN# N10330. Consequently, that code will always be there as there was no software change in the Climate Control Module.

That means you'll have to go back to the other possibilities for the heat all the time; most likely the DCCV, the Control Panel or a wiring fault.

Good luck!

 

Thanks Steve,
That advice saved me a whole lot of time, expense and potential hassle. Back to the DCCV/CCM investigation path. I hope it is the DCCV/CCM - that seems relatively easily fixable.
Regards,
Chris

 

Turns out that this was the DCCV/CCM issue after all. The B1265 DTC code was, as Steve suggested, a red herring. I've done the DCCV replacement and I'm now tackling the CCM fix myself. Anyone know how to add a diode to the CCM module to prevent the board from blowing the next time there's a DCCV issue? I know there are various rebuild options but I figure I can save myself $300 if I do this myself...

 

A diode? Sounds like the wrong part.

 

There's a company that will repair the CCM and add a diode to prevent that DCCV from shorting out the CCM in the future.

 

How does a diode stop a short?

 

From Wikipedia:
Diodes are frequently used to conduct damaging high voltages away from sensitive electronic devices. They are usually reverse-biased (non-conducting) under normal circumstances. When the voltage rises above the normal range, the diodes become forward-biased (conducting). For example, diodes are used in (stepper motor and H-bridge) motor controller and relay circuits to de-energize coils rapidly without the damaging voltage spikes that would otherwise occur. (Any diode used in such an application is called a flyback diode). Many integrated circuits also incorporate diodes on the connection pins to prevent external voltages from damaging their sensitive transistors. Specialized diodes are used to protect from over-voltages at higher power (see Diode types above).

 

None of that applies. There will be no high voltages.
I think someone has wrongly used the term diode.

Clearly what is needed is to prevent overcurrent, thus preventing the PCB traces being burnt out. That's not a diode.

 

How about a simple 1A, or 1,5A fuse? Wouldn't that work?

 

Yes. Just have to figure the right value.

 

I went down the diode track after reading a thread on the forum (now I can't find it) that indicated a diode was the solution. A fuse does make a lot more sense though... I think I'll just put a 1A fuse on the pin and bypass the burnt trace. I think it's a reasonable bet that a 1A fuse would do it - I vaguely remember a thread that indicated that a broken DCCV will send as much as 18A back to the CCM.
Thanks for putting me back on the right track.

 

Well now, hold on...... you may be overlooking something. I'm not sure exactly what the panel repair guys use, but it may involve what's called a CLD. They are Current Limiting Diodes, and can prevent some over-current conditions. I don't know whether they can be used directly, or used to limit the base current and therefore the controlled current of a small power transistor. Either way I think that's how they do it.

I long ago determined the nominal resistance of the DCCV solenoids to be 15 ohms. Ohm's Law tells us that would mean normal current to be just a small hair under 1 amp.

What happens is the valve solenoids either short some windings or fill with coolant and the resistance goes down, current goes up and the trace inside the control panel pays the price. [just yesterday a co-worker had to repair a valve and panel, and the DCCV solenoids measured 3 ohms and 6 ohms]

The first order of business for me is to measure the two solenoid resistances. I believe I've headed off numerous control panel repairs by doing so. If the resistance is below 13-14 ohms......it's gotta go!

Cheers,

 

If you are interested this is the company that reapirs the modules and can add the protection circuits if you want.

Repair & Upgrade - JaguarClimateControl.com
.
.
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Thanks xjrguy. Is it possible to measure the resistance without removing the DCCV?

 

Hi XJRguy,
I ended up following the burned trace from the inbound pin to a marker on the board (IC-7) which is a component that looks suspiciously like a Zetex CLD (edited: actually turned out to be a Semens BSP 78). I put a jumper wire directly from the inbound pin onto this component (it has a single input and three output pins). I think that component is what is saving the rest of the board from overcurrent (by blocking the 18A), and because there is a feeble trace between it and the pin the trace burns up in overcurrent conditions. To be extra safe I'm probably going to add a 3A fuse on the 18 guage jumper wire so that I'm guaranteed the jumper wire won't fry at 18A. If the DCCV goes again, I should just have to replace the 3A fuse on the jumper wire. I am no electronics genius but this seems it should protect the board from the DCCV overcurrent conditions(?). If this works, I've saved myself $250 in repairs and (because I'm in Canada) $60 in shipping, for the cost of a little bit of solder, a 3 amp fuse and 2cm of 18 guage wire.

 

This, I think, is the component on the CCM board that I soldered the 18 guage jumper to (and to which the burned trace was leading):
http://www.diodes.com/datasheets/ZXMS6003G.pdf
edited: Actually it is the SIEMENS BSP 78
http://pdf1.alldatasheet.com/datashe.../datasheet.pdf

 

If that Zetex chip is already there, all it looks to need is the right setting to current limit (so we get overcurrent protection, one of its stated features).

BTW, it's not a diode!!

 

My theory is that the Zetex (ed. Siemens BSP 78) chip is already set to the right overcurrent setting to protect board components and that these post-2004 boards have a simple design flaw by putting a standard 35um trace ahead of the Zetex (ed. Siemens BSP 78) chip. If so, the Zetex (ed. Siemens BSP 78) component would stop overcurrent and protect the board, but the design flaw putting (the maybe .75 amp, 35mu) trace leading to it from the pin leaves the trace vulnerable up to the Zetex's (ed. Siemens BSP 78) programmed overcurrent cutoff amperage. I could probably figure out what that limit is by looking at the resistor installed across the STATUS and IN pins on the Zetex component... That the board probably survived overcurrent (there is no visible damage to other traces or components) with only the trace burning during the overcurrent condition would seem to suggest that this is true (?). The trace acted like a 1-2A fuse by burning.
Anyway, I'm going to play it safe and make sure I'm not simply exposing the rest of the board to overcurrent, by putting a 1A fuse on the jumper wire that I can replace in case the DCCV goes again. If it blows under normal operation, I'll increase it to 2A.
Thanks to everyone for helping me reach, hopefully, the right conclusion.
The dealer can take their DCCV/CCM fix quote of $3000 and shove it. My solution: Bosch OEM DCCV part: $200 + $40 coolant + $6 electrical repairs + 1 1/2 hrs of my labour. Fingers crossed!

 

Yes, thanks, I get that now. I need to preface all my theories with "I am an electronics novice, at best" if that wasn't obvious already!
The reason I went down the "diode" path was that there was talk (in other posts) that the rebuild service providers just add a "diode" to the circuit to stop overcurrent. The only diode that can do that is apparently a "current-limiting diode", not a basic flow-direction control diode. The (apparent) Zetex (ed. Siemens BSP 78) chip on the board has a current-limiting feature built-in which (should) negate the need for even an additional current-limiting diode, as long as the wire/trace leading to it from the pin can handle the current before the Zetex (ed. Siemens BSP 78) chip overcurrent feature kicks in.
Either way, I'm adding a 1A fuse to the jumper just in case...