No Heat/New Blend Doors - DIY FIX [Part 1] ;-) - Jeep Forum - Forums and Owners Club
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  #1  
Old 10-23-2012, 12:20 PM
RobH RobH is offline
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Post No Heat/New Blend Doors - DIY FIX [Part 1] ;-)

I've owned my WJ Cherokee for 8 Years. I love it but they do have quirks. My latest experience is 'Blend Door' Failure; indicated by a sudden but total absence of heat in the car.

This seems to be a 'popular' WJ feature and a big issue judging by the number of posts out there....

Anyway my heater is now fixed !! ( just in time for winter )

I bought the materials I needed at 'B&Q' (Hardware) and used ordinary tools I have in the garage to make a new set of the 'blend doors' - I think anyone reasonably handy can do this and so avoid repair bills or the need to purchase any jeep or custom replacement parts. The instuctions seem long - but it's actually a simple job - I've just included all the details.

My cost for the materials used was less than 10 ($20?) and the job took me about 2 hours.

I've signed up with this forum to share how I did it.

First of all I have to say thanks to the many other contributors out there who posted instructions about this fault. If you have this problem with your jeep (no heat) It's worth trawling the net for information to make sure you've diagnosed the problem area (Like how to access and understand the Heater/AC system fault codes display) and to get pictures and instructions.

Especially helpful to me were posts/pictures on how to get at the blend doors without removing the dash! (i.e. by cutting into the heater ducting behind the glove box)

I researched all this beforehand so I knew what I was looking at and where eveything was (Important!)

Materials used:

2 @ 8 x 11cm pieces of 2mm thick Aluminium Sheet
2 @ 8cm lengths of 10mm copper pipe (As used with Micro bore central heating )
1 @ 2cm Length of 8mm Aluminium Tube
4 @ 4cm Lengths of copper wire (approx 1mm Dia)
4 @ Pop Rivets
Epoxy Resin Glue (Optional)
Solder (plumbers version rather than electrical)
Solder Flux (Optional)
Aluminium Adhesive Tape

Note: The 2mm thick aluminium sheet is quite rigid - (anything thinner might flex and that would be a problem)

Tools:

'Dremel' drill with cutting bit
Jigsaw ( with metal cutting blade)
Small Hacksaw
1 Medium File (half round)
1 Small/Thin file - Triangular or half round
Drill & bits - 1mm & 1.5mm
Pop Riveter (Hand Tool)
Sandpaper
Gas Blowlamp (for soldering)



These were the steps taken:

  • Removed the glovebox, unscrewed the 'actuator' motor and pulled out the plastic 'spigot' which locates in the blend door spindle. Keep this part safe - it's needed later!
  • Cut into the plastic heater duct using a 'Dremel' tool fitted with a cutting bit. (But I suppose a small size drill or even a small hacksaw blade would do the job)
  • I followed the instructions and diagrams found on other sites to make sure I cut in the right area and was careful so I didn't damage the heater core inside. This wasn't difficult and the job took about 5 minutes.
  • I did make sure to do reasonably tidy job of the cut as eventually this piece needs to be re-used. I also removed and retained the metal clip for use later. [PIC 1]
  • Use Dremel again to remove the piece of plastic (which can be discarded) between the two blend doors and expose the second blend door farthest into the heater duct.
  • This gives full access to the blend doors. I reached inside and pulled both out. ( Being careful in removing the inner door from it's corresponding motor spigot )
  • As expected both doors were broken at the point where the 'spigots' locate and the foam covering had disintegrated. [PIC 2]
  • I then used the two doors as a pattern to manufacture replacements and re-used the actuator motor 'Spigot'
  • Cut 2 @ 8cm lengths of the 10mm copper heating pipe.
  • Check that the pipe ends are smooth and open enough so the 'spigot' is an easy fit - if not clean pipe inside with small file.
  • Then cut to size a 2cm piece of the aluminimum pipe and insert to check fit inside each the copper pipes ( The aluminium pipe will be used as a 'centre spindle' between the two new doors so needs to fit snugly inside the copper pipes) [PIC 4]
  • Cut out 2 @ 8 x 11 cm pieces of aluminium sheet to form the new doors. The doors are only 10cm long but a 'fixing' tab is needed - hence the extra length. [PIC 3]
  • Check fit inside each copper pipe and note the length of the 'spigot' when fiited (this will later determine where the fixing tab ends must be) Similarly check where the aluminium pipe (spindle) will extend.
  • Using these dimensions mark out a 'fixing tab' each of the new aluminium doors and cut away where required. [PIC 5]
[Continued in next post with further pictures ]
Attached Images
File Type: jpg PIC1 .jpg (44.2 KB, 33 views)
File Type: jpg PIC2.jpg (57.7 KB, 26 views)
File Type: jpg PIC3.jpg (57.4 KB, 24 views)
File Type: jpg PIC4.jpg (68.0 KB, 23 views)
File Type: jpg PIC 5.jpg (59.6 KB, 24 views)
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Last edited by RobH; 10-24-2012 at 06:31 PM.
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  #2  
Old 10-23-2012, 08:06 PM
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Excellent writeup so far. Looking forward to part 2!
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  #3  
Old 10-24-2012, 04:26 AM
RobH RobH is offline
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Default Post No Heat/New Blend Doors - DIY FIX [Part 2] ;-)

  • Also mark and cut out the small section on each door to match the original door shape.
  • Now pair and mark up each copper pipe and each door (left & right)
  • The next job is to solder two pieces of copper wire inside each pipe. These will form fixings which correspond with the two grooves on the actuator 'Spigots' and enable the motors to turn the spindles.
  • You will find that the spigot fits nicely into the 10mm copper pipe [PIC 7 ] ....
  • But the spigot grooves do not extend all the way to the base so the wires will have to be fixed about 0.75cm into the pipe.
  • It is vital that the wires are postioned precisely so that the spigot will 'mate' correctly. To assist this process prepare two pieces of wire for each pipe. Each wire needs to be about 4 cm long. Now fold the wire in half and crimp it firmly to make a U shape 'staple' that can be 'clipped' into the pipe and will stay in place whilst you solder it. [PIC_8]
A note here - The AC/Heater computer carries out regular 'tests' to position the blend doors. This involves the actuators rotating each door until it meets the end of it's travel and cannot move further. This 'stop' puts a strain on the motor which in turn produces and increase in amps. The amp increase is detected by the computer to confirm the end travel position. Consequently the door spindles are regularly put under strain. The original part has a small 'stop tab' on each spigot ( which breaks off - causing all these problems !) I have not replicated the 'stop tab' in this design (you could if you wish) The finished doors are very much stronger than the original plastic version but it is important that the 'spigot' locates well into each copper pipe end to form a secure fit so take time to make this bit as accurate as you can.
  • Insert the 'spigot' and mark where the two wires need go to line up with the grooves in the spigot. [PIC 9]
  • Now make two cuts with a hacksaw in the end of each pipe corresponding with the positioning of the wires. If necessary enlarge the cuts so that the wires will fit.
  • Now insert the two wire 'staples' into the grooves and postion the wires so they are parallell in the pipe. Don't worry that half the 'staple' is on the outside - this is removed after soldering [PIC 10]
( Continued in Part 3 )
Attached Images
File Type: jpg PIC 6.jpg (56.0 KB, 14 views)
File Type: jpg PIC7.jpg (63.6 KB, 14 views)
File Type: jpg PIC_8.jpg (70.8 KB, 15 views)
File Type: jpg PIC_9.jpg (54.6 KB, 19 views)
File Type: jpg PIC 10.jpg (70.6 KB, 18 views)
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Last edited by RobH; 10-24-2012 at 06:59 AM.
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  #4  
Old 10-24-2012, 05:19 AM
RobH RobH is offline
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Default No Heat/New Blend Doors - DIY FIX [Part 3] ;-)

  • Now check the alignment by inserting the spigot with the wires in place [PIC 12]
  • Carefully remove the spigot to avoid heat damage; Make sure the pipe is clean for soldering inside (apply some solder flux if available) place the copper tube -with the wire staples in place - in a vice at a slight angle (so the solder will run) heat the pipe with the blowlamp and run solder down the inside of the pipe to fix the wires in place. Check that you use enough heat so the solder doesn't block the pipe but not too much so all the solder runs out. The finished job should just be a coating of solder over the wires inside. [PIC 13]
  • Once it's cool cut the external part of the wire away and clean up the outside of the pipe removing any excess solder. Complete this process for both pipes.
  • You now need to cut slot in each copper pipe to recieve the door and 'fixing tab' you made.
  • Mark out where the slot needs to be on each pipe to correspond with the dimensions of your fixing tab. (I used a marker pen)
  • Note - Ensure that when it is inserted; the 'tab' won't interfere with the spigot wires you just soldered in place or the insertion of the aluminium pipe 'spindle' at the other end.
  • Important : The slot also needs to be orientated so that it is cut at a point more or less centred between the two spigot wires. Hence if the spigot wires are positioned at 12 o'clock and 4 o'clock then the slot for the tab needs to be at about 2 o'clock.
  • then put the tube in the vice and using a 1mm or 1.5mm bit carefully drill a series of holes along your mark.
  • Only drill through one side of the pipe.
  • Clean up the line of drill holes using the dremel or a file/similar to produce a slot that will neatly accept the fixing tab - it doesn't have to be pretty but if the fit is better the door will be (even) stronger.
  • Now insert the fixing tab in the slot, ensure the tab extends all the way to the 'back' of the pipe and that the tab also lines up against the outside of the pipe without too much clearance. If necessary use a file to shape the tab to acheive the best fit.
  • Put the whole assembly back in the vice, check everyting is lined up OK and drill two holes for pop rivets through the pipe (one side only) and into the fixing tab. Then pop rivet into the tab to fix it in place. Make sure the door 'plate' is at 90 degrees to the pipe when fixed. Repeat this for the other door assembly [PIC 14]
  • For good measure I applied 2 part epoxy resin glue all around the tab but being careful not to get any glue inside the ends of the pipes.
  • Insert the piece of (8mm) aluminimum pipe to form a spindle between the two new doors. Check the whole assembly fits together well and especially that the spigot locates easily and snugly on the locating wires in both pipe ends.
  • You have now manufactured two replacement blend doors, they may be a bit untidy round the edges and not absolutely precise but they are very much stronger (and not much heavier) than the original parts and they should work OK. [PIC 15]
  • Important: When fitting the new blend doors the near one will be no problem but you will have to 'press fit' the pipe end onto the spigot of the far actuator at the back of the heater ducting - To avoid any risk of dislodging the (hidden) actuator this will need to be acheived carefully and without too much force so the parts do need to fit together fairly smoothly. It's worth taking time with the small file and/or sandpaper to smooth things out and make for a snug fit.
( Continued in Part 4 )
Attached Images
File Type: jpg PIC 12.jpg (68.3 KB, 18 views)
File Type: jpg PIC 13.jpg (70.3 KB, 15 views)
File Type: jpg PIC 14.jpg (65.6 KB, 17 views)
File Type: jpg PIC 15.jpg (65.9 KB, 16 views)
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Last edited by RobH; 10-24-2012 at 07:24 AM.
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  #5  
Old 10-24-2012, 06:18 AM
RobH RobH is offline
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Default No Heat/New Blend Doors - DIY FIX [Part 4] ;-)

  • Before fitting I used a small amount of 'copper grease' (heat resistant) lubricant on the spindle and spigot ends.
  • Fit the 'far side door' first - Insert the aluminium spindle in the copper tube then offer the 'spigot end' of the door making sure it is correctly located on the motor spigot and then drop it into place so that the new spindle rests in the centre section between the two doors. [PIC 16 & 17]
  • Then offer the 'near side' door copper tube to fit it onto the spindle in the centre; then align the other end with the hole in the duct side ready to accept the spigot.
  • Note: The precise length of the protruding aluminium spindle can affect this operation and I found it necessary to take a couple of millimetres off the spindle with a file to give me just enough room to align the door correctly.
  • Insert the spigot and replace the actuator motor.
  • Now to test that the doors actually work by recalibrating the AC system as follows:
  1. Turn the ignition on.
  2. Set the AC/Heater to automatic.
  3. Turn the ignition off.
  4. Remove the 'IOD fuse' (50 amp fuse No.15) from the Power Distribution Center (Fuse box on the left of the engine bay )
  5. Wait 30 seconds - then replace the fuse
  6. Turn the ignition on. Don't touch any of the Heater controls for at least 2 minutes to allow the calibration process to run.
  • You should see the doors move independently as the calibration test runs through...
  • If not check for free movement and any obstructions. If necessary take the door assembly out again and re-install it.
  • Once you are happy that the doors operate correctly re-insert the piece of heater duct plastic you removed; line it up correctly and replace the metal clip. Then seal over the cut you made using a couple of pieces of aluminium tape. [PIC 18]
=================== Job Done ======================


Note: The orginal doors are covered with foam, this deteriorates badly and I am not sure what could be used as a (better) replacement - Hence I have not used any sort of foam etc on my new blend doors and I don't notice any difference in the heater output. I suppose there may be some air 'leakage' which may affect hot or cold AC performance - and the lack of foam may cause the system to report 'Large Travel' - but I'm ok with that - at least I've got some heat !


Finally

Thanks for reading. If you have a problem with broken blend doors I hope I've helped - Please do leave your comments about this fix - It may not be a completely 'as is' replacement or even as good as the custom parts that are available - This was a DIY solution which cost no more than a few pounds -
But it's worked


OTHER SITES I FOUND USEFUL FOR REFERENCE:
Attached Images
File Type: jpg PIC 16.jpg (57.0 KB, 22 views)
File Type: jpg PIC_17.jpg (49.1 KB, 20 views)
File Type: jpg PIC 18.jpg (49.0 KB, 20 views)
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Last edited by RobH; 10-24-2012 at 06:24 PM.
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  #6  
Old 10-24-2012, 06:19 PM
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Great job RobH! This will certainly help anyone with blend door issues.
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Old 11-20-2012, 12:05 PM
RobH RobH is offline
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Update - Still working fine after 1 month - But I decided to reinforce the plastic 'Spigot' with a metal pin replacing the (broken) original plastic tab - just so there is something for the motor to act against when the system goes through the 'check postion' routine (which it does after about 20 'ignition on' operations I think)

( An all-metal (aluminium?) replacement for the plastic spigot would be a good preventive fix - Jeep Chrysler Please note !)
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Last edited by RobH; 11-20-2012 at 12:12 PM.
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