Range Rover P38 # 067 - Troubleshooting HEVAC Motors
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- Опубликовано: 13 сен 2024
- The blend (and recirculation) motors can be tested using a 9V battery. Apply power to the two wires that power the motor (black wire and brown wire at C1597) and watch if the lever moves. Reverse wires to move it the other way. Do NOT apply 12V power as it could overheat and burn out the motors.
The recirculation flaps are easily monitored by taking out the fans. These have only two wires to the motors and no feedback to the control unit (White/Green and Black/Green for the right side, and White/Red and Black/Red for the left side). Use either the C0791 connector at the HEVAC (in front of C1597) or the connectors near the flaps on each side.
Always disconnect the connectors at the HEVAC control unit before you test using the 9V battery.
Connector 1597 and 0791:
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Blend and Distribution Motor wiring:
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Recirculation Flap Motor wiring:
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Resistance values for left blend motors (between pin 8 and 13): ~8kΩ on HI and ~2.5kΩ on LO. Right blend motor is between pin 7 and 5.
Resistance values for left blend motors (between pin 8 and 14): ~2.5kΩ on HI and ~8kΩ on LO. Right blend motor is between pin 7 and 1.
Note it can vary by ±10%. And anything in between 2.5 and 8kΩ depending on what temperature you set.
Distribution motor resistance varies between 4 and 6.5kΩ (most likely 2.5 and 8kΩ here too but I couldn't get mine to move fully to either end position.
The above are for the feedback circuits (on connector 1597 at the control unit) and not actual value of the motor itself. The blend motors itself measure around 40Ω (I've seen 30 to 70Ω in my cars).
The blower motor regulation voltage can be measured at pin 3 for the left fan (connector 0791 at the control panel) and pin 6 for the right fan.
At lowest fan speed the voltage is approx 10V (9.5 - 10.5V), and at full speed it is approx 4V. If you set the temperature controls to LO the voltage is around 10.5 - 11.5V. At HI temperature the voltage decreases to 0.3 - 0.6V.
A few more good guides on the blend motors:
www.rangerover...
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It is nice that we have you “out” there. Thank you.
Thankyou thats really helpful
Love your videos and hopefully you can help. I have a 95 P38 and had it in the shop for some brake lines being repaired. Went to pick it up and found that 1) gear shifter would not indicate it was going into "Park" or "1"(transmission does into park and 1 (shows "R" and "2" respectively) but not indicated), 2) Car will only start in "N" and key will not come out when in "Park" (again indicator shows "R" when in park), and 3) Blown Fuse #8 - no radio, Cigar lighter, or HEVAC..WHAT I HAVE DONE: Relay #7 under hood was melted so replaced fusebox..no other obvious faults...when bypassing BeCM and providing 12V to White with Pink feed to HEVAC and Radio, I get proper display, but no action by HEVAC nor any Radio...any ideas? Its getting cold and I need heat!
I've throw in some measurements in the description. They include the resistance you should expect to see from the feedback circuit of the blend and distribution motors, as well as resistance of the motors themselves. Please check the diagrams linked in the description too. I also added voltage measured for the blower motors at various speed. Note that if you set the temperature to LO or HI other voltage values are observed since the HEVAC control unit then enables full fan speed automatically. I hope these help you guys troubleshoot your systems. But as always, start with checking the trouble codes with a diagnostics scanner.
It was a nice description.Do ypo know how to open roofwindow.It has stuck.I cant take with key either.
Oh hey..my ac system doesnt face the front.its blowing through the dash infront of the windscreen only
Hello, I would like help, I have a range rover p38 and I have a problem with the roof. when I close it it is in the right position it is what under the sky of the car ... in order to find it in the right position I have to do it manually .. I have to do some operation ..
My p38 blower motor on the driver side is tripping and burning up the wire for the relay underneath the the hood in the engine bay what causes this
I struggled to get to the blend motor on the passenger, I gave up.
Today I tried a different attack, I found the wiring diagram for the blend motor, I got access to the connector by removing the radio, the connector for the blend motors is on the left side of the heater unit, It is stamped 1 to 8 on one side and 9 to 18 on the other, from memory pins 11&12 are for the PS 9&10 are the DS. You need to disconnect this connector to carry out the below.
On mine the drivers side was stuck giving a slightly warm air flow, passenger side blew cold constantly, I connected some thin solid core cables into pins 11&12, using a 9v battery I powered up the motor which drove for only a short time, it must have just been on the fully cold setting, just reverse the polarity to drive the motor in the opposite direction, the motor drove fully over, I did the same with the drivers side.
Sure enough I now have heat on both sides, I would have been happy to leave it like this, and just redo it again in summer I was expecting the motors to stay in the position I had driven them to, but after going up and down the heat scale on both sides, checked using a digital thermometer they were now working correctly to heat and cool, happy days, it even cleared the check manual warning sign on the unit.
It would appear the motors were just stuck / lazy from lack of adjustment by the previous owner I'm going to keep exercising them, fingers crossed they keeping working, nothing to loose, and far easier that trying to get access to the motors buried in the dash somewhere.
The grease in the motor casing gets old and sticky instead of helping lubricate and the parts to move freely. Glad the diagrams and schematics in the description of the video helped you out to bring life back to the sticky motors. Thanks for watching.
What code reader do you use to get these codes?
Hi my P38 ac isn’t blowing hot air, what should I do?
Hi Magid. Sounds like the blend motors are stuck or defective. Most likely just stuck due to old grease which clogs up and prevents the flaps from moving. It will be easily determined by reading any fault codes stored in the HEVAC controller. Thanks for watching!
Have you ever replaced the screen? Mine often has issues and I see there are replacements.
I have not replaced the screen but seen many who have here on RUclips. I forget if it was the P38 or the Mercedes that had issues just with the connector to the screen. Both of mine have held up fine so far at least. Just had to replace the bulbs. Thanks for stopping by and watching.
Hi great video. My P38 sometimes has the book with ! On and then there is cold air coming from drivers side and everything else has hot even when set to cold. Could you tell me how you find out what diagnostic code it is. I can’t find anything about the air con self diagnostic symbol how to find what fault there is.
Hello Jaroslav and thanks for stopping by my channel. To be sure what the problem is you'll need to read the error codes from the HEVAC (heating, ventilation and AC). Check out my video # 16 to see which diagnositc unit I use: ruclips.net/video/9Cs6AnZvSBc/видео.html The fault seems to indicate that the heater blend motors (determines how much cold or hot air) might be sticking or faulty. Good luck and I hope you find out and manage to solve your issue. Thanks for watching!
My fan is working but don’t have hot air comming out what would this be
blend motor not working what side is it if its the passenger side its an easy fix
Have you done any work on the AC system, or does it work on both your cars?
Hello, yes I've fixed both the P38s AC-systems. Both had leaking condensers but I replaced all o-rings and the dryer plus switches to keep the system working for a long time. Check out video 60 ruclips.net/video/N9fJtNcBK1U/видео.html video 62 ruclips.net/video/OBwrIBj7m3s/видео.html and video 63 ruclips.net/video/iAxaCDZeYhg/видео.html plus video 80 ruclips.net/video/yqvNj10DxM8/видео.html might also be worth checking out. Thanks for watching!
Found all those videos after watching more and more, thanks. Looking to buy a 01 P38 now, no cold air but no book in the display either.
Hi, A yallow light beside dashboard always twinkling, I think it is standby alarm. How can I turn it off ? Because I only use car key, I never use remote key, and I don't want to waste battery.
Hello and thanks for watching. I don't think it makes a difference if you use the key or the remote to unlock or lock. It basically performs the same task. To avoid battery drain from the remote control system you'll need to disable the receiver in the trunk. The receiver unit picks up anything on the 433MHz band and wakes up the car all the time which causes a battery drain. Do you mean the light in the center and on top of the dashboard? That blinks when the alarm is active, and I don't think you can do anything with the key or remote to disable it when locking. I think you can program the BeCM module to disable the alarm with special diagnostics tools / software. Not sure if my Hawkeye tool can do that, but I'll check some day as I think it might.
Hello, I would like help, I have a range rover p38 and I have a problem with the roof. when I close it it is in the right position it is what under the sky of the car ... in order to find it in the right position I have to do it manually .. I have to do some operation ..