Author Topic: cabin fan system question (1988 pickup)  (Read 410 times)

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KauriJ

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cabin fan system question (1988 pickup)
« on: Jan 12, 2020, 01:03:28 PM »
Iím hoping someone here can point me in the right direction of how I can solve two (small) issues with the cabin fan system in my momís 1988 Toyota pickup.

When I turn the cabin fan on, leaves/fir needles/etc. come out of the air vents into the cabin. I had a similar problem with my 4Runner, and I ended up just needing to clean a mouse nest out of the blower fan. Iíve removed the leaf debris that was in the pickupís blower fan, but thereís still a lot (!) of stuff coming out of the air vents when I turn the fan on, especially when switched from recirculation to outside air.

Iím guessing all this debris is probably originating near the air intake, but I havenít found a diagram of where the air intake is for the cabin fan system, and if itís different than the air intake for the motor. (Incidentally, there was a small mouse nest beneath the engine air filter, so Iím thinking mice could be to blame for this issue.) I do have a copy of the book How to Keep Your Toyota Pickup Alive for the Compleat Idiot (which is appropriate for my skill level :) ) and the 1988 Toyota Truck and 4Runner Repair Manual, and itís possible that Iím just looking in the wrong places for info.

The second issue is that the lever for adjusting the temperature on the cabin fan/heating system seems to be jammed at about the midpoint, and thereís occasionally a rattling sound from that area when the truck is moving. (Hopefully not another mouse issue?) Would I be able to access this area if I take apart the dash, or is the box containing the controls for the fan system totally sealed?

Any advice regarding how to fix these issues will be greatly appreciated! (Including pointing me to a thread that I missed when searching on this topic :) ) Thank you!

KauriJ [OP]

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Re: cabin fan system question (1988 pickup)
« Reply #1 on: Jan 12, 2020, 08:55:47 PM »
I think I may have found the answer to my first questionÖ. If itís like the newer pickups then the air intake should be under the wiper tray/windshield cowl, so hopefully cleaning it out from there will make a difference.

arlindsay1992

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Re: cabin fan system question (1988 pickup)
« Reply #2 on: Jan 13, 2020, 03:42:30 AM »
To answer your first question, yes the intake is under the windshield cowl. Remove the wiper arms, then pop the hood to access three Phillips screws and two push pins that hold the cowl to the cab. There are big holes in the cab for air to flow in. Some trim levels have plastic screens that pop in to provide a rudimentary filter. If you're interested, I have a set. If your truck was originally equipped with A/C, the A/C evaporator in the dash is a big collector of debris since all HVAC air flows through that no matter what the temperature selection.

To access the controls you really need to remove the entire dash. Nothing is sealed, it can all be accessed and serviced, it's just a pain. I wouldn't be surprised if the heater valve under the hood is frozen or or stiff. This puts a large strain on the blue HVAC cable, which might have bent. Also, when stuff stiffens up, sometimes the HVAC control assembly simply cracks. So don't force the levers if they are stiff. A good teardown, clean, and lube can make all the HVAC move like butter and save precious parts from breaking.

KauriJ [OP]

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Re: cabin fan system question (1988 pickup)
« Reply #3 on: Jan 13, 2020, 02:02:06 PM »
Great, thank you for the detailed explanation! Iíll remove the windshield cowl as soon as I get a Phillips screwdriver with a short enough handle so itíll fit under the hood and I can take those three screws out. :) I donít know if it has a plastic screen, but Iíll check. And thereís no A/C.

Also, thank you for the advice about the heater valve and HVAC, and that I should not force the levers to move! Iíll try to take things apart and clean them, and see how far I get; if it turns out to be beyond my skill level Iíll bring it to a professional mechanic. Do you have any recommendations for minimizing the risk of breaking parts when taking apart the dash? I admittedly donít have a lot of practice with things like this but I hope to learn. :) Thanks!

KauriJ [OP]

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Re: cabin fan system question (1988 pickup)
« Reply #4 on: Jan 25, 2020, 06:20:44 PM »
Iíve successfully removed the windshield cowl and cleaned out the leaves, fir needles, and mouse nest by the cabin air intake, which will hopefully solve that part of the problem. (Iím a bit embarrassed I didnít do this first, since it was full of debris, some of which is now in the blower fan, so Iíll be cleaning that out againÖ) Thank you to arlindsay1992 for the advice on this!

In regards to the second issue, Iíve partially taken apart the dash, but am having trouble with the passengerís side register. Following the instructions on page BO-45 of the repair manual, it looks like there are four clips that Iíll need to push down to remove it. Iíve gotten it partially out on top, but am not having any success with finding the bottom set of clips. I did see a YouTube video which indicates that, once the top is partially out, the vent part needs to be removed from the ďframeĒ of the register, and the clips pushed down from inside to get the frame out. But Iím not sure how to get this vent part out.

Iíve also pulled off the cover for the controls for the fan system (sorry if it has a more precise name that I donít yet know!) and can see the levers and the blue HVAC cable. This may be just showing my ignorance, but how would I know if the blue HVAC cable is bent and should be replaced? Also, the metal lever for adjusting the temperature feels wobbly top-to-bottom, and is stiff trying to move it left-to-right. Could the problem just be that it is bent or loose somewhere? Thanks!

arlindsay1992

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Re: cabin fan system question (1988 pickup)
« Reply #5 on: Jan 27, 2020, 09:26:01 AM »
The passenger side register is very difficult to remove without breaking. I would recommend leaving out the bolt that goes behind it when re-installing the dashpad that way you don't have to worry about it in future dashpad removals.

Once you have the HVAC control panel out you'll be able to see if the cable is bent. It should be straight with only a deliberate manufactured shape to engage the levers. It should slide freely inside the blue cable sleeving. Without seeing it, I can't say for sure the cause of the wobbly lever. It's all snap together so it shouldn't really wobble. Tight is fairly normal on an unserviced HVAC control panel. I cleaned the cables with brake parts cleaner, then lubed them all with either silicone spray or maybe WD-40. It's been a while so I don't remember for sure but either would probably work.

KauriJ [OP]

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Re: cabin fan system question (1988 pickup)
« Reply #6 on: Jan 27, 2020, 09:56:12 AM »
The passenger side register is very difficult to remove without breaking. I would recommend leaving out the bolt that goes behind it when re-installing the dashpad that way you don't have to worry about it in future dashpad removals.

Once you have the HVAC control panel out you'll be able to see if the cable is bent. It should be straight with only a deliberate manufactured shape to engage the levers. It should slide freely inside the blue cable sleeving. Without seeing it, I can't say for sure the cause of the wobbly lever. It's all snap together so it shouldn't really wobble. Tight is fairly normal on an unserviced HVAC control panel. I cleaned the cables with brake parts cleaner, then lubed them all with either silicone spray or maybe WD-40. It's been a while so I don't remember for sure but either would probably work.

Thank you!!

From what I can see with the HVAC control panel off, the cable looks as you described, straight with only a deliberate manufactured shape, but I'll (try to) take more of the dash apart so I can better see the cable and lever, and also if something else is bent or broken.

 
 
 
 
 

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