1984/1985 Toyata Pickups heater blower fans not working "Low" setting but otherwise working fine

toyota

#1

Hi, My Wife has a 1984 and I have a 1985 Toyota Pickup, 2wd, 22R engine, same dash and almost same everything. There are 4 settings on the selector switch (horizontal lever switch moving from left-to-right) for the blower fan: “Off”, “Low”, “Med” & “High”. In both trucks, the “Low” setting for the BLOWER FANS quit working, but the other settings still work fine and amount heat-output is fine(so this is a FAN problem and not a “heating” problem).

Is the problem in the switch itself?, or in the blower fan resister?, or in the blower fan moter? From what I’ve read elsewhere, it seems to be a blower fan Resister problem that is most likely. If that is the case, where exactly should I be looking for it and will I need to remove the dashboard? And what does it look like? I’ve seen a small black object about 1"x 1.75"x 1.75" and it has an Amperage listing on it and it’s next to a Relay that seems to be related to the heater. I’m guessing that thing is not the resister if it’s labelled “Amperage”, I would think it should have an “Ohms” symbol or word or rating on it if it were the resistor, or is that really “it”.

Thanks - Paul


#2

It’s the blower resistor.

For the low setting, the voltage passes thru two resistors. For the medium setting the voltage passes thru one resistor. And on the high setting the voltage passes thru no resistors.

Tester


#3

Sweeeeeet!!
I had both a 1979 and a 1989 and I loved both of them.

The stepped resister network Tester described is located mounted on and into the ductwork on the passenger side behind the dashboard. The air flowing through the ductwork is used to cool the resistive element to prevent the elements from burning out. You can access it by lying on your back on the passenger floor and looking up with a flashlight. You’ll see the back of the resister network, the connector and its wires. NOTE: I remember that my blower motor was mounted using “torx” (star) drive bolts. They’re like allen bolts, only with radial slots rather than a hexagonal hole. You can pick up star heads at the local dollar store. Fort one-time use they’ll be fine. I don’t recall whether the resister network used them too, but it can’t hurt to be prepared. Once you get yourself folded up under the dash, you’ll want to get the job done before unfolding your body.

By the way, I bench tested my blower motor using a simple 9VDC transistor radio battery. You could even use a 6VDC lantern battery. DC motors use variations in the applied voltage to control their speeds. The resisters simply “drop” (convert to heat energy) some of the voltage when you go to lower fan speeds, leaving lower applied voltage at the motor. I didn’t bother to run “ohm’s law” arithmetic, but 9VDC and 6VDC are probably close to what the motor sees when you’re on lower fan speed.


#4

You aren’t the only one with this problem on a Toyota @Pauliwog … the “lo” speed on my early 90’s Corolla’s burned out years ago. I can access that resistor gadget if I wanted to by removing the glove box I think, but being on the lazy side, I just use the medium setting instead. hmmm … Maybe I’m thinking “Being somewhat of a fatalist, if I fix that problem, then with nothing wrong remaining, something worse is bound to break. Better just live w/it”!

The reason the “low” speed is the one that burns out is b/c the way it is wired, the power is shared between the motor and the resistor. In “hi” all the power goes to the motor, none ot the resistor. In “low” less power goes to the motor, so more goes to the resistor and it heats up more.


#5

Considering I had my '79 for almost 11 years (don’t remember the mileage) and my '89 for over 338,000 miles (before it got hit), I can live with a burned out resister network. Besides, in the days when those open-element stepped resister networks were used it wasn’t unusual for one to burn out on an old vehicle no matter the make.

I have to admit, though, that the iron in my ‘79 must have loved oxygen… that vehicle did rot somethin’ awful. Oddly, the '89 had no rust problems throughout its entire life. Same climate, same driver, same maintenance. They had apparently solved the rust problems. Then, on later models, the rust problem apparently returned. Toyota even had a recall where they changed the entire frames.


#6

I still have my 1984 Toyota pickup, SR5 manual trans. It’s been awhile since I last changed its blower motor resistor but it is held on by a single phillips screw as I recall and there is, of course, an electrical connector attached to it. There are no amps or ohms markings on mine. There might be an H, M (or M1, M2) and L visible on the side facing out. No need to remove any dash parts. If you want to know what it looks like, you can look it up on an online auto parts store.


#7

Here is pics and schematic.


#8

Hey, Thanks to everyone for all that good info and quick responses!
Knfenimore- Thanks for posting the schematic and picture, that’s a big help for sure.

Adios - Paul


#9

Keep in mind that sometimes failed resistors are a symptom of a problem rather than the cause of one. An aged and dragging blower motor pulls more current (meaning heat) and over time that can burn up resistors or fan selector switches.


#10

Hey, I found the resistor, got a new one, opened up the vent-duct system and cleaned everything out of the blower fan, around the motor, etc. When I removed the original “burnt-out” resistor, it was encased in packed lint that was sooooo dense, it was like felted wool. It was soooo well thermally well-insulated, I’m betting that is the main cause of it burning out. I put the new one in this morning and it works fine thus far.

Hopefully tomorrow I’ll do the same with my truck, the 1985 Pickup (the aforementioned is in regard to my Wife’s 1984 Pickup). I’m betting I’ll find my resister similarly encased in some sort of uninted collection of insulating “stuff”. I’ll keep everyone posted.

Thanks again for all the input and feedback. - Paul


#11

The new resistor(s) will probably do it. But keep in mind, as ok4450 said, that if any part of the resistor blows again, you need to look at the blower motor itself.


#12

Thanks a lot Folks. You just saved me $35.00 for a new switch and pointed me in the correct direction as to where the little rascal is located.


#13

Hey, I got the Blower Motor Resister into the 2nd truck(my truck, the 1985 pickup), and when I opened up the vent system(by removing the section behind the glove box), it wasn’t as dusty or full of debris as I had expected from the same procedure on my wife’s truck, nor was the burned out resister encased in the same bundle of compacted lint. It still had enough dust to make it worthwhile to clean it out. I replaced that resister with a new one also and it seems to work fine for now. We’re probably going backpacking the next 3-4 days (don’t know where yet) and it will be a good test as we drive one of our trucks for our trip.

I decided to buy a 3rd spare resister for future use as we both intend to keep these 2 gems of vehicles as long as we possibly can, they’re real “Keeper’s” for sure.

Good to know about the possibility of the blower motor itself being a possible cause so I’ll keep that in mind if we get another burnout on the any resister coils. And I’ll definately post something if that happens. Since we’re talking 1984 and 1985 (30 and 29 years ago when built), and these resisters have never been replaced that I’m aware of, I’m guessing long term use of something that gets hot and is thin and in the presence of oxygen is the most likely cause of the burn out. But, again, good info that was brought up about the blower motors.

Thanks again - Paul


#14

Hey, Well, we did’nt go backpacking due to the weather, but I did get the chance to drive around with my vent/hearer/defroster fan blowing on a nice smooth “Low” setting on my truck, the 1985 2wd. So far, so good.

Thanks again for everyone’s input, it’s ALL been helpful and relevant.
-Paul


#15

Thanks sincerely for the follow up post. It’s good to hear of a happy ending. We so rarely hear the ending.


#16

One more followup, My wife and I mostly bike-commute so we don’t drive either of our trucks much but both have had occassion to use the “low” setting on the fan since my initial installation and both are working fine!

Thanks for all the input everyone! - Paul