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Discussion Starter · #1 ·
Tired of not having any heat (other than my toasty heated seats) I decided to go all in on the upgrades.

I pulled the old heater box, cleaned off 30 years of dirt, replaced the fan with the newer PM136 fan, enlarged the bulkhead vent hole, and was planning on the larger Allisport heater matrix. I was expecting to have to modify the heater box as described in this video:


However, the new Allisport core I got (DA4743 from LRDirect) fits into my existing heater box perfectly and I don’t have the lower and upper apertures that need to be modified in that video. The new core is a little thicker, maybe 25% than the original heater core.







So… Did I get the wrong heater matrix? Is there some later/earlier heater box that I have? Should I shut up and just put it all back together?
 

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How much time in your shop does this project take? Looks like a good upgrade. My Webasto Thermo Too C is a great addition. Upgrading radiator core and blower would seem like a good addition to utilize the Webasto.
 

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So regarding upgrading heater - all tgr defenders I’ve had the Fan switch is basically binary … emitting noticeable Ali less blowing full bore.. the one or two intermediary steps never really seem to blow any air.

Is there an upgrade to the switch as well?


Sent from my iPhone using Tapatalk Pro
 

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Does your water temp gauge get to proper operating temp?

keep us posted on the project and the results... looking to do the same to my 90 as I also have no heat (planning to drain the all the coolant and use a vacuum system to refill).
 

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I did this three days ago. PM136 mod, Allisport straight pipe mod. Sandblasted rust off box, replaced all internal gasketing, used straight pipe Allisport matrix. Nothing tricky. Just a bit of cutting on the top and bottom shrouds to get it nice and pretty. The hardest thing was the gasket on the back side of the internal flap as that has gasketing on both sides. The outer flap just has it on one side and a small strip on the backside to prevent clanging around. You just want to make sure you have gasketing on the inside sides of the box pressing on the full length of the sides of the matrix to prevent air from getting around it. See posts 86-92 here: 1991 200TDI to R2.8--couple remaining questions

Feel free to stop by if you want to see it.
 

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Discussion Starter · #10 ·
Thanks @Davis!

I hadn't realized that you were journaling your R2.8 build over on NAS-ROW. I can confidently say that I'm doing about 40% as good a job on my truck as you are on yours! Yours looks great!

@sheki - Yep, the truck heats up pretty quickly and stays consistent. Once I got the heater box out I'm pretty sure that the heat diverter flap wasn't working properly.

@sundogcwolfe - I'm doing the work myself (too cheap to pay someone but I enjoy tinkering). From a timing perspective, so far:
  • about an hour to pull out the heater box
  • 30 minutes to cut the bulkhead hole
  • 30 minutes to modify the new fan's wiring
  • an hour to clean (wire brush on my grinder, degreaser, scrub) the box
  • an hour to clean the bulkhead, spray paint, put some soundproofing on
Next:
  • Install/seal the new heater core (an hour?)
  • put it all back into the truck (an hour?)
  • Bask in my new warmth (a lifetime)
Updates to come...
 

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Thank you the great time breakdown. Than is very helpful. My Rover projects on hold a week or two. Got some recovery time after a trip to the Mayo. Coming home to find two of my kids tested positive. Everyone feeling OK and are vaccinated and boosted. hot Toddy time.
 

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Updates to come...
If you don’t mind, can you take some temp readings after the install?
Out of the lower vents when open, the front hose and the rear hose (and the ambient temp)

I just ordered the Allisport heater matrix. Should be here on Monday and will do the same. Thx!
 

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Discussion Starter · #13 ·
I got the heater box buttoned up and put back in the truck. It's pretty fiddly to get the bolts to line up but I did it right (because I did it twice!) :) I didn't get the gasket right between the wing intake and the fan housing itself, but it's pulling plenty of air in so I think I can live without it.

The fan is loud on high and seems to be clicking a little so maybe something is loose or rubbing a little. I'll need to sort that out. But...

I keep blowing the 10A blower fan fuse. I haven't 100% confirmed it, but it seems fine when the truck isn't running, just on Accessory. I can turn the fan on/off and switch between High and Almost Non-Existent blower modes, and if I start the truck I can turn the fan "on" with no problem, BUT when I cycle the fan on/off a few times while the truck is running I blow the fuse. This never happened with the old fan.

Any ideas/?
 

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I just checked my new PM136 fan's amperage with it running and it pulls 1A pretty consistently and will have an initial start up peak of about 30A lasting just a fraction of 1 second which is typical of a motor on start up and typically not enough for any fuse to blow as it doesn't give the fuse enough time to melt for a typical blade fuse (and isn't a concern on start up). HOWEVER, if you have any motor drag, then the start up will take longer and could easily spike and last longer than a fraction of a second which would blow the fuse (or have the potential to do). You should not have any noise with the exception of it sucking/blowing a lot of air. You should definitely not have any clicking. That to me makes me feel like there is a binding going on. One area of common issue is the wire coming off the brush. Typically the "hard wired" brush is out of the way routed through a tiny hole in the board that keeps it tucked away from the rotor. The other wire that you invariably soldered, may be rubbing on the motor or you may have the squirrel cage offset to the point it is potentially rubbing. You could also potentially have a short although that is less likely due to the fact that it works once running. When you have an issue just on start up, that leads me to think of binding is happening.

Personally, I would start by taking an amperage reading on the blower---I would disconnect the resistor, apply 12V directly to the two wires on the motor lead and use a clamp on or in line amperage tester and see what you get. An analog one will be easier to see the spike, but I have a fairly good digital one that can at least see a little what is happening. An oscilloscope or recording meter that can measure spikes is ideal.

You can also take a look at the wiring to the fan and make sure that there is not anything secondary on that line creating a secondary draw.

What I would not do is just increase the fuse size. It should not be blowing and fuses are sized to the wire---to prevent the wire from breaking down and causing even worse issues...

I'd be happy to take a look next time you are up this way, too.
 

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Discussion Starter · #17 ·
I pulled the heater box back out (only took about 20 min!) and found that indeed something was rubbing, likely causing the spike in current draw/fuse blowing.

The squirrel cage was rubbing on the "Spacer Tube Flanged Condenser" (number 11 here).

I didn't put the foam gasket in (number 12 on that diagram) so do I really need to put the condenser back? I know it will then be pulling some air from the engine bay versus just through the wing vent, but is that such a bad thing?



 

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That spacer tube can just be pushed up inside of the air inlet to keep it from rubbing. I would also keep the foam gasket that you are omitting.

Not only are you pulling in carbon monoxide to the cab you're also pulling in smelly fuel air and road debris.

You don't need to buy the expensive gasket you can just use foam rubber Frost King weather stripping.

If you look at the diagram that you linked you can see that you had the spacer tube inserted in backwards.
 
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