Paging VStar - Fan speed controller resistor

[AZhitman]

G'day sir! Figured I'd go straight to the guru on this one.

1991 Pulsar GTiR (N14 chassis, but very similar to a B13). AC compressor kicks on, cool air in the vents, but there's no blower motor (3 settings, none work).

I'm told the common culprit is a burned spot on the resistor, so I started searching for it. I found what LOOKS to be the correct part (on the actual squirrel cage housing).

Here's what I found:

There are two "bubbles" in the tracks, which I assume are burns or corrosion.

Now, I'm being told that there's another fan speed resistor somewhere behind the HVAC controls, but this seems inconsistent with the part's function (and other Nissan designs).

I'm also told there's a replacement available, Part # 27150-62J60 - but mine has a different P/N.

So, my question is: Did I find the culprit, and am I OK to order the same P/N?

Big hugs buddy! Thanks for all you do for our audience!

[VStar650CL]

If it's the same as the old Sentras then it's not a VBC. It's a regular resistor with 3 segments, but the internals are printed, not wirewound. That one looks the same as all the other the old shark-fin resistors, but you're right, the part number doesn't match up and the one printed on it doesn't show any supersessions. Is the blower switch 3 positions plus OFF, and does that resistor have 4 contacts? If so, there's a good chance the -62J60 will work anyhow but the blower RPM's might be a little different. You might actually want to see if it will come apart, all of those old resistors had internal fuses in series with the pin for the motor wire and some of those fuses were silicon (not part of the printed circuit). Those can be desoldered and replaced. So if the fuse is popped and the problem isn't a burnt resistor element, it may be repairable.

[AZhitman]

3 positions + off, and yes, 4 contacts.

Already ordered a replacement, so I'll update upon arrival.

Would there be any reason for this to NOT be the only fan speed resistor? Some of the other owners are saying theirs is behind the HVAC controls, but after pulling the center stack apart, I see no such thing.

[VStar650CL]

There's no reason I'm aware of why there would be a second one. Maybe they're confusing it with the Thermo Amp for the A/C.

[AZhitman]

OK.

New resistor arrived.

Fan still not operational. I now hear a click (relay?) going from off to auto, and a click from auto to 1. No click to 2 or 3.

I pulled the dashpot but it appears to be a sealed unit. Guessing I should pull the actual blower and test it next?

[VStar650CL]

I'm not sure what the Auto position would do on something that old, but I'm guessing it just lets the blower follow the A/C. Speed 3 should be a direct connection to ground through the switch, bypassing the resistor. It will all be located on the ground side of the blower, that's true of all Nissan blower circuits. The blower relay can be located north or south of the blower fuse, so the fuse having juice doesn't necessarily tell you anything.

Is the blower hard to reach? If not, start by turning the key on and the switch to 3, then see if you have juice at both blower terminals. One should be bright, one dimmer with a test lamp. If both are dark, the problem is likely the relay. If one is bright and the other is out, the blower has bad brushes. If both are normal then the problem is either in the switch or the switch ground.

[PapaSmurf2k3]

only fan

Wait... you're launching an Only Fan's page?

[AZhitman]

Removed blower motor. Tested with 12v, dead. Decided to disassemble it, the entire motor casing is full of black sooty dust, like graphite... So, I assume it's toast.

PN is 57503-30350, but all I'm getting for that is s*** from Russia. I'm wondering if I can replace the motor with another 91 Nissan blower motor (they all seem to have a 3-bolt housing connection and I assume the same drive shaft).

Wish I'd pulled that FIRST instead of d!ck around with the HVAC controller and such.

[VStar650CL]

That black dust is what's left of the brushes. They're usually graphite doped with small amounts or copper or silver. If you can't find a replacement you could consider having it rebuilt by Eurton Electric, those guys can rebrush and recondition damn near any electric motor ever made.

[VStar650CL]

only fan speed

Wait... you're launching an Only Fan's page?

Hey, keep it in context. Boobs and speed... s#ityeah, I think that's a great idea.

[AZhitman]

WOO!

Well, I tried a cheap replacement that * looked * correct. Probably could've jury-rigged it to work, but the squirrel cage was a bit larger and the shaft diameters were off by 1mm.

So, I ordered a replacement motor only component, should be able to R-square it and be good to go. To be continued!

[AZhitman]

OK, replacement motor in and functioning. Almost there.

Question: Is the blend door function vacuum or electronic? I'm not getting "switching" across the various vents with key on, but hoping it might require engine vacuum.

ALSO, there's a corrugated tube (about 1" diameter) off the back of the HVAC control module. I remember disconnecting it, but can't for the life of me find where it was connected. I assume it's for temp sensing for AUTO mode?

[VStar650CL]

On Auto systems the tubes always go out to the cabin someplace, usually a vent in the lower dash. I dunno on something that old, you're straining my brain. I got out of the business to go do engineering around '83, right when the first serious cabin electronics were coming out. I can tell you how befuddled customers (and us too!) were when the Maximas got the first digital radios.

I checked ASIST and there's no online documentation for the NX's, the FSM's in ASIST only go back to '94. However, all the B13's I've ever seen with pushbutton HVAC had electric actuators for Mode and Recirc and a cable for Mix.

[AZhitman]

Gotcha. I'm hoping I don't have a failed actuator. I'll get under the dash again tomorrow and see if I see anything obvious... Grr.

Thanks brother!

[VStar650CL]

[AZhitman]

BTW, we have the FSM. https://www.nicoclub.com/service-manual ... Manual.pdf

[VStar650CL]

Trouble is, the 90~95 copy seems to be incomplete, it ends after EF&EC. The '89 has an HVAC section but it only shows cables, no options for pushbuttons or Auto. So I think we're in guessing game territory.

[VStar650CL]

Okay, I take that back. The one titled "Workshop" is actually Volume 2 and has all the other stuff. It's mislabeled, they're Vol 1 and Vol 2 of the same FSM. What it shows is that my guess was correct, Mode and Intake are servos and the heater control uses a cable. The wiring diagram is on PDF page 906, HA-84.

[VStar650CL]

From what I can tell, it looks like the Mode actuators can still be had (pricey, but available). Part number is 27731-40F00. They were used in the Max, 240, and Stanza in addition to the B13/N14, which is probably why they're still around. The Intake actuator (recirc door) is p/n 27740-64J00 and looks to be unavailable in the 'States, but still in stock at Amayama.

[VStar650CL]

Amazingly, it looks like there are also still a few button control heads available here in the 'States, p/n 27510-65Y00. The superseding part shows unavailable anywhere, 27510-65Y01, but you might be in luck even if the control head is the problem.

[PapaSmurf2k3]

Who would have thought airflow would be so complicated.

[AZhitman]

Today's episode of Pure Agony:

As you know, this started off as just replacing a bad blower motor and resistor card. I replaced both and still got no real airflow (I have good RPMs on the squirrel cage and can switch between the 3 fan speeds).

So I started checking the fresh/recirc door, the airflow selector (foot / dash / def), and the heat/ac servos. Of course, they weren't functioning. So, I figured I could manually set them to "AZ spec" (no heat, recirc, dash vents) and save myself some headache. Did that, in the hopes I could restore airflow. BTW, those servos are NEVER going back in, there's simply no room and I don't even know if the issue was my head unit or the servos themselves. BUT, I figured as long as I have max AC, I'll be happy, and I can use the car.

Considering I still had no meaningful airflow, I borescoped the evap box and found it's chock full of debris, and the evaporator is totally clogged (like a huge mass of fuzzy funk). So, I was hoping to disassemble the blower motor housing and the evap box, and be able to get in there and give it a good cleaning.

I've been at this for 2 days, I have a cereal bowl FULL of hardware, and I'm getting nowhere with being able to remove the evap housing clamshell.

I'm beginning to think I'm stuck pulling the dash. Which means cracking the AC hard lines, which means disassembling a ton of underhood stuff to even access them. I'm frustrated beyond belief.

THIS is why cabin filters are a great idea. The prior owner of this car ("Oh yeah, it's got good AC") can pucker up and kiss my aggravated arse.

[AZhitman]

On Auto systems the tubes always go out to the cabin someplace, usually a vent in the lower dash.

Found it. It's a "air sample" tube for the Auto setting, and found where it goes. (That's now the LEAST of my problems).

[AZhitman]

HVAC buddy came by to service our home AC units today. He's also a B13 Sentra guy.

While sharing my misery, he suggested detaching the high and low pressure lines at the firewall, and the whole assembly should come out.

There's a lot to remove to get to them, but if I've come this far, I may as well. I really want to clean the condenser and condenser box on the bench, so that's tomorrow's agony. Wish me luck!

[VStar650CL]

Crossing fingers and toes.

[AZhitman]

So, in a last-ditch effort to save myself a ton of dismantling, I hooked up a shop vac in reverse and stuffed it in the port between the squirrel cage box and condenser box with some rags to direct the airflow. I STILL have no meaningful airflow from ANY vents (where the hell is all that air going?)

Is it possible that a filthy, clogged condenser can stop the airflow THAT much? I guess it can...

BTW, I scoped the downstream tract and the heater core is pristine - guess the condenser caught all the funk.

Back at it tomorrow. I'm really, really not looking forward to this. A simple effing cabin filter would've saved me 20 hours of work.

[VStar650CL]

The problem with A/C evaps is that they get wet in operation. That means a junk-clogged unit like yours can actually become a dried-mud clog. If it's that far gone, you may have no choice but to remove it and hit it with a power washer.

[AZhitman]

OK. I probably needed that reassurance that I wasn't about to waste more time.

Thx brother!

[PapaSmurf2k3]

Man those window-mounted evaporative cooling units like you have for your wagon don't sound like a bad idea right about now.

[AZhitman]

Hahahaha, if the Thermador worked worth a s***, I'd have one on every car!

So, I got the condenser and airbox out. It's been soaking in cleaner all day, and I can see daylight through it now. Tomorrow, reassembly.

I'm gonna add more insulation to the in-box hard lines to reduce sweating, and replace the foam perimeter pieces.