FJ40 Heater / Fuse Gremlins

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michaelharrisco

michaelharrisco

10 Year 15 Year
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Jul 18, 2010
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Raleigh, NC
I searched a bit (i.e. gave it 5 min) on the main mud site and didn't find anything that helped so wondering if anyone here has any thoughts or experience.

Today I turned on the heater on the 40 (insert jokes, but yes I got cold on my way to work today with the doors off). Nonetheless, the heater quit working and my temp, oil and fuel gauges all went to "zero" while driving. Blown fuse was my first thought and I had planned on replacing all the fuses anyways because they were visually looking a little rough.

I've never got a good answer on what Amp to use on the 40 fuse box. I replaced all the fuses per this cover picture attached. Now, nothing electrical such as lights, signals, dash on the truck is working at all (I am able to crank it an drive it though).

Two questions:
1) Anyone know why turning on heater would shut off gauges and quit working blower motor after a few minutes?

2) Anyone know proper A for fuses in FJ40 (1978)?

fuse-box-cover.webp
 
Fusible link is my first guess. (is there a fusible link on the FJ40s?)
 
I know there is a "in line" fuse for the carb cooling fan.

I played around with the fuses in the Auto Zone parking lot today at lunch and put in all new ones per that image and it made things worse (i.e. no lights or signals, etc).

I'd really like to know the proper fuse amp for the FJ40...it sure does seem like I could trust the fuse box cover info I found online (I don't even have a cover at the moment).

Then once level set get back to figuring out why turning on the heater blower knocks it off / blows fuse somewhere.

I'll look through my Haynes manual when I get home (I know they can suck sometimes, but the schematics in the back are nice)
 
IMG_0842.webp
I've never seen a black cover before. There are a couple of different covers that I've seen listed as 1978 with different orders of circuits. Some have a small fuse at the bottom, some don't. Mine is a 9/77 and I'll look for my pic of the cover and edit here when I find it. I'd suggest reading through the entire thread posted by Rudi:
https://forum.ih8mud.com/threads/clusters-gauges-speedo-odo-meters.544543/

Found it. This cover came on my truck but I can't verify that it is correct. I've got the short fuse at the bottom (radio 5A).
 
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I would also recommend you take the 2 10 / 12 mm wrench bolts out that are holding the fuse box to the wall right there and make sure all wire looks good back behind the fuses. And clean the contact areas up a bit also. Might have some crusty s*** on them from over the years.
 
JohnVee said:
View attachment 945417 I've never seen a black cover before. There are a couple of different covers that I've seen listed as 1978 with different orders of circuits. Some have a small fuse at the bottom, some don't. Mine is a 9/77 and I'll look for my pic of the cover and edit here when I find it. I'd suggest reading through the entire thread posted by Rudi:
https://forum.ih8mud.com/threads/clusters-gauges-speedo-odo-meters.544543/

Found it. This cover came on my truck but I can't verify that it is correct. I've got the short fuse at the bottom (radio 5A).
Click to expand...

I have the short fuse at the bottom. I'll switch around fuses tonight and clean up things + check wires.

Thanks for posting.
 
I put all new fuses in per the white fuse box cover and everything came back online like it should.

Oddly enough...this still happened:
1) turned ignition to "on" (i.e. not cranked, but full elec on)
2) checked everything and all checked out
3) turned on heater, stayed on ~1 min then shut everything down
4) I figured, fuse blown...so I swapped in the HEAT fuse for a new one.
5) everything came back on...like it should
6) For kicks, I reinserted the same fuse I just replaced and everything still worked (i.e. the fuse didn't blow from the heater)

Something somewhere else has to be going on with this heater.

I ran out of time, but I'll review schematic in more detail.

I was not able to find any fusible links by the battery from a first look, but I was short on time last night.

By the way, if anyone has the fuse box cover like the one JohnVee posted...let me know if I can buy it from you.
 
My 75/40 has a ballast resistor on the main blower in the engine compartment, pass side fire wall. Look on top for the ballast. Sounds like that is acting up There is a thread that I've looked at on the main forum that gives you a place to order one. I'll try and find the link on the other computer.
 
Thanks for the insight...I'm not familiar with that particular part, but know exactly where you are talking about. I'll take a look / try to test if possible.

If you find that link, please send over because I'll probably just order a new one.
 
Don't worry about digging up link...I found a few options for a new one. The dealer is also looking to see if they can still get a new one (not sure on price though).

I located the part last night (right where I thought it would be).

Question: is there a way to test this part with a multi-meter? What measurement range should I find across it or are there other ways to test it to know if it is good or bad?
 
If it is the resistor on top of the heater motor, I think it is 8 ohm's and is only used for the first speed setting and is bypassed when things go to high and run the rear heater. I am speaking from an '82 point of view, so yours might be different.
Not laughing at turning the heat on this time of year, best part of my daily driver (Volvo) to Charlotte is the heated seat in the morning.
 
Its very interesting you say the part about the low speed, because I did finally find a write up on the main forum where people described this exactly. Now thinking the problem I'm having...turn heater on and it only stays on for ~1 min and then shuts off and kills gauges is something different than this resistor on the top of the blower.

I may be back to the drawing board...I'm going to test it tonight and check a few other wire connections to make sure something else isn't tripping up the system.
 
Well folks....it appears this has just been a blower motor dying a slow death. Tonight confirmed the blower motor isn't working. I'm thinking something odd was going on as it died and caused other odd stuff to other items like the gauges that are on the same circuit.

Guess I'm now in the market for a new blower motor. Give me a shout if you have one.
 
Or how about this....not 5 min after posting that last message I decided to give the top of the blower motor a couple of love taps with my BFH (very softly)....tada it has now been running great.

Any thought on root cause? I'm wondering if just not running heat all summer got it gummed up? Or a classic fj40 gremlin?
 
You might as well go ahead and start looking for a motor. A lot of times as the motor dies, tapping the housing will free up a locked rotor condition, and allow the motor to spin and work for a short period of time. Eventually that "trick" will no longer work.
 
Pulled this from a '88 (62) today. I do not know if it could be interchangeable but it looks like the same resistor. Does this look anything like yours? I will check if it turns in the next day or so.
image.webp
 
It looks similar. Mine has been working since the love tap, but who knows for how long.

Is yours working / anyone know if this would work in mine (78 FJ40)?
 
Coinop, if Michael does not want your fan and resistor I am interested in the resistor at the very least. Maybe the whole nine yards. I'm installing heat in the Crockpot and my resistor is fubar'd. Let me know.
 
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