Help with AC diagnostic code: B1265
 

I've got a 2000 4.0L S-type and the AC has not worked since I purchased the car 5 years ago. I've decided to get to the bottom of it. I took it in for a diagnostic and I have attached what the mechanic found. (see attached image).

In short, the ac system works, but the cold air is not making it into the cabin. Its throwing a B1265 code and the mechanic says he cannot hear any signs of the cold air bypass door working when switching from hot to cold.

I have checked the climate control module for shorts (found nothing) and tested the 4 blend door actuators that are mounted on the left and right of the climate control (heater core/ac evaporator housing) directly behind the center button/navigation panel (all work great). Is the cool air bypass servo completely hidden such that it can not be seen by taking the center control panel out/lying on the driver/passenger foot wells and ONLY seen by removing the entire dash?

I want to make sure there is actually another blend door actuator in there before I remove the entire dashboard.

Also, any pointers as to what else (other than a blend door actuator could be causing this issue would be appreciated.

https://cimg7.ibsrv.net/gimg/www.jag...975760fdd9.jpg

It may be the control module circuit board that has failed.

Prior to conducting any further diagnosis, make sure the battery has a minimum of 12.6 volts across the terminals with the ignition in the OFF position when checked with a voltmeter. If not, charge the battery for six to eight hours at 2 to 5 amps and retest. If the voltage is still below 12.6 volts, the battery should be replaced for the vehicle to function normally.

Assuming the battery is good, have a read of this thread that Karl went to great lengths to provide:

https://www.jaguarforums.com/forum/s...2/

Hi,

I looked into your B1265 fault code and found some conflicting information. I may have to revise my troubleshooting guide to reflect this.

At some point in production, the HVAC system was revised and this cold air bypass door and actuator was deleted. However, the controller software was NOT updated, so you'd always have this B1265 fault code. The customer would never see this code, so Jaguar never bothered revising the software to prevent this nuisance message. It seems in most cases, you can just ignore this message as it means nothing.

Can't remember where I found the info when I wrote the guide, but I had been thinking there was no door and actuator to bypass the heater core. But now I see it in some training guides, but those documents are usually preliminary (pre-production) information and do not always show what was actually installed. Any info you find in a training guide must be taken with a grain of salt.

Sorry I don't have a clear-cut answer for you about B1265. But what I can suggest is to work through my (potentially flawed) troubleshooting guide:

https://www.jaguarforums.com/forum/s...ol-how-185002/


You can do most of the troubleshooting yourself with just a thermometer. You don't need to pay a professional to do it. Work through the steps in posts #2 and #5.

If your car indeed has this mystery cold-air bypass door, we don't know in which position it has failed. If it has failed in such a way to let airflow through the heater core, there's a good chance your Dual Climate Control Valve (DCCV) has failed in the open position. The DCCV has a very high failure rate. The DCCV is supposed to shut off hot coolant flow to the heater core when cooling is requested. If the DCCV misbehaves, you may be getting so much uncommanded heat that it is overwhelming the normal output of the AC side of the system. Your shop measured 110F air exiting the ducts, which makes me think your DCCV has failed open. Unless it was a 110F day, that is well above ambient. That tells me the situation is more than just refrigerated air not reaching the ductwork. In that case, you'd have ambient air temperature from the ducts. It seems more like unwanted heat being dumped into the system, which points to a problem with the DCCV or its control circuit.

Please keep us posted. This is an unusual scenario, and I hope we can find a resolution for you.

You are right Karl...have a read of this..https://www.picoauto.com/support/viewtopic.php?t=17761

Remember, there's no need to type that out. Think of all the bandwidth that would be tied up if everybody stated the obvious... ;)

Interesting link. Note the car mentioned there was a 2006, near the end of the production run. For this thread, the car is a 2000, quite early.

After reading the linked page, I had a bright idea. (Sorry, I know, hogging more bandwidth again...) The guy mentioned how this actuator wasn't even in the 2006 wiring diagram, so I looked through the wiring diagrams. Figure 06.1 is the HVAC system for all years:

JagRepair.com - Jaguar Repair Information Resource

Sure enough, all years show this "cold bypass actuator" except for 2005+. Dang, that means I've been less correct than usual. Who'd have thunk? Sorry for any consequences, such as the earth lurching from its axis, stuff like that.

Back to the car in question, though. It still seems like the DCCV is letting hot coolant reach the heater core when uncommanded. That's the only way you could get such high duct temperatures, regardless of the position of this door. I would take care of the DCCV issue first and see if that restores proper cooling.

Just thinking out loud, but I wonder if the B1265 code has something to do with duct temps higher than ambient, and so the controller thinks there's something wrong with this door. I don't know how sophisticated the monitoring system is. I could be out in left field, so don't read too much into this crackpot theory. Just a thought, really.

I did come across this as well. I assumed it only applied to later model years.

FURTHER INFO: The vents (when the AC is on cold) blow ambient air untill the heater core is turned on or the car sits outside (hot) in the sun. This makes me think that the evaporator is not turning on/cold air is not making it to override the ambient engine bay temperature/temperature of the heated up heater core. After a drive with the air on, the vent air eventually returns to ambient temperature.

This really does seem to be an issue with getting the cold air past the evaporator. Are there any diagrams that show where this cool air bypass door is located. As I said, all the actuators I am able to see are working fine.

Thanks

Big issue with this line of thinking. The cold from the AC does NOT override the output of the heater core. This is very important. For the moment, please put the function of this cold air bypass door on the back burner. I think that door just helps speed up the cooling operation, such as when you switch from heating to cooling, and the heater core takes a few minutes to cool off. We can come back to that later. When cooling is requested, the DCCV shuts off all flow of hot coolant to the heater core. The AC output is not overriding the heater output. There should be no heater output. Zilch, nada, zero. No hot coolant flowing through the heater core, and thus no heat to be overridden.

That's why I strongly suggest you verify the DCCV is completely shutting off the flow of hot coolant when commanded. It's very easy to do, as detailed in my troubleshooting guide. Fix the known faults first, and then we can move on to anything else.

Even if this door is acting up, you may find the AC output returns to normal if the likely DCCV problem is corrected. Remember, we don't even know the logic that sets the B1265 code. I'm busy learning all this as we go, trying to sort it all out. Or you may find the B1265 code remains active, but if the cooling is now good, I personally wouldn't worry about the door.

If you absolutely, positively want to get to that actuator, I found this illustration from the training guide for 2003 models:

https://cimg3.ibsrv.net/gimg/www.jag...46e9158e34.jpg


If earlier models are the same, you looking at item #8. This should be accessible from the left side of the center stack, above the gas pedal on a US model. I know #7 is accessible on an early model because I've stood on my head to replace it.

I also know that 2003 picture isn't quite accurate, as it also shows item #2, a "temperature blend door actuator" for which I could find no reference for any model years.

I can put my hand on the heater core pipes through the control panel (which I've removed) .. and they do not get hot until I turn on the heat. I would assume this suggests the DCCV to be working.

Also, I can verify that the actuator (#2 in the picture) is working.

This isn't exactly a valid test due to one factor. The results could be misleading. The coolant flow through the heater circuit is marginal at idle. If you've ever noticed the heater output drop off while decelerating or sitting at a light, that's why.

If your DCCV isn't closing fully, you may not get much heat at idle, which I'm presuming is when you're doing your test of the pipe temperature. But at higher speeds, with lots of coolant flow, you may be getting plenty of uncommanded heat dumped into the ducts.

I'd highly recommend running the test of the DCCV exactly as written. The test was carefully composed to minimize external factors like that.

I'd also recommend springing the $20 for an infrared thermometer, versus using your hand to see if the pipes feel warm. Unless your hand is freshly calibrated, you can't really tell the difference between 80F and 100F, for example.

But wouldn't I be getting at least some signs of cooling then? Certainly the evaporator would override the heater core until the heater core warmed up. Right now it is either ambient or whatever temperature the heat is set to. Zero signs of cold whatsoever.

AC performance is also marginal at idle. The compressor is spinning at slow speed, and airflow through the condenser is at its lowest. Testing at idle, you may have a pair of 98 pound weaklings fighting each other. Who wins? Anybody's guess.

I don't know what else to tell you, other than to fix the known faults first and go from there. Does your car have a DCCV problem? Not sure, but it certainly seems like it. Run the test I've given and then we'll know for sure.

First off, I would like to apologise for my stubbornness. I ran the test and the bottom line (of the three on the inside of the fender leading back to the firewall got extremely hot. The lines into the heater core behind the dash seemed much cooler but still slightly warm to the touch. It appears a DCCV problem may be present after all. I'm assuming the next best step is to replace the valve? I have checked (and replaced for good measure) the #1 fuse in the front fuse box.

You can clamp off the hoses to take the DCCV out of the equation.

Two other considerations:

• When the system was recharged, there is a note that several of the seals on the refrigerant circuit are leaking. Has anything been done to eliminate the possibility that refrigerant is being lost continuously?
• Was there excessive refrigerant high circuit pressure when the system was fully charged? If so, there could also be a problem with the expansion valve restricting the flow of refrigerant.

Other known areas of system failure are the discharge sensors, items 4 and 6 in the drawing,

Be careful. The temperature test of those three lines is supposed to start with a cold engine, as in sitting overnight. From there, you initially run the engine at idle with the hood open. These steps are very important to minimize radiant heat from the adjacent exhaust manifold. Since you had previously been running the engine, all that radiant heat may have given a misleading indication of a bad DCCV.

The troubleshooting guide has two methods to test the DCCV. If you don't want to wait overnight (or at least several hours, preferably longer) for the engine to cool, run the test of the duct temperature with the AC switched off. Don't do this at idle in your driveway. Go for a test drive and work the engine a little. Keep the revs up to compensate for low coolant flow at idle. You want to stress the DCCV as much as possible for a meaningful test.

You will need a little pocket thermometer ($5?) to accurately measure the air temperature. Don't just guess by holding your hand to the vent. You need a fairly accurate measurement, to make sure the duct temperature is no more than 5 degrees or so warmer than ambient. That seemingly small margin can be the difference between a good and bad valve. There's no way to discern that small difference with just your hand.

A variation on that test is to clamp off the two small lines, as Norri has suggested. Remember to switch off the AC so any uncommanded heat isn't inadvertently cooled, thus appearing to test okay. Once again, I recommend a test drive to stress the DCCV for best results. You'd probably need to make two runs, with and without the clamps, and then compare the results.

Any updates? This is a very interesting thread, as we have not had any problems with this bypass door, at least that I can remember. You may be something of a pioneer sorting this out.

Once the problem is resolved, I plan to update the troubleshooting guide with this new info. I’m very curious what you find, especially if the DCCV is part of the problem. I’ve been waiting all day with bated breath, hoping you had time for more testing.

It very well could be others have had this same actuator issue but didn’t realize it, as most scanners can’t retrieve B fault codes. My current thoughts are this particular actuator fault won’t totally inhibit cooling action, but I don’t know for sure.