50 amp heater fuse keeps blowing ‍‍‍

So the blower switch sends a ground (or +12v) to the relay to activate it, then the relay sends +12v to the blower (with the 50A fuse in series) and each speed position except high (direct) inserts resistance on the ground lead based on the setting via the blower resistor?

Sorry if I have that backwards or have inverted ground and +12v in places. Maybe a while back you posted a wiring/switch/fuse schematic. Trying to understand the connections for reference.

 

Correct, the switch controls the ground to the HEATER Relay to turn it on, power for the load side of the relay comes from the 50 amp HEATER fuse (hot at all times) and power for the control side of the relay comes from the 10 amp IG1 No2 Fuse (hot in run).
The switch also controls the ground to the blower motor, it regulates the speed by changing the ground path through the blower resistor and providing direct ground to the motor on high.
I have a detailed description of the power flow for the blower here.
https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/#post-28042158

 

@Dm93 Where could it likely be shorting if you had to guess

 

Not sure, it could be anywhere but typically I look where harnesses are rubbing on things.
You could unplug connector IA4 and see if the wire is still shorted, if it is then the short has to be between there and the fuse box under the hood, if it isn't then the short has to be under the dash between there and the blower motor.

 

Have you looked at the resistor connector?

 

That wouldn't blow the fuse, the resistor is on the ground side of the circuit.

 

Do all Gen 2 Tacomas have the Floor Wire, and Floor Wire No.2 & No.3? One appears to be under the driver's seat, and the other in or under the center console.

 

I'd have to look at other year diagrams but they probably do, the wiring routing and harness joining connectors didn't change a whole lot over the years.
Why do you ask?

 

Although it's a crude alternative to the ideal aftermarket heated seat kits - I have 2 of those inexpensive heated seat covers. They work ok, and the Honda CR-V I had provided a receptacle in the center console. I drilled a small diameter hole for a cable to exit which I connected to a dual 12v receptacle for the heated seat pads to plug into. I liked that the wiring was pretty much concealed. I don't think the Tacoma has a 12v receptacle in the center console (does it?) but if that 12v feed is accessible near it, or under it, or maybe Floor No. 2 Wire I could use that.

 

There is no 12v feed under the seat or console that I know of that would support seat heaters other than maybe the one for the power inverter on equipped trucks and I think that's only powered up when the inverter is turned on.
The floor No2 wire I'm pretty sure is just for the SRS System and the seat belt switch.

 

So out of curiosity If my heater blower relay is blown with that cause my 50 amp fuse to blow as well? Because I finally went and got a test light tonight and pulled the cap off my relaying tested it and it did not come on

 

I’m not sure what you did, or tested?
The relay should not come apart. It should only unplug from the fuse box.
How did you test the relay?

And did you use the test light to test anything?

 

I suppose it's a possibility but I have never seen a relay short out and blow a fuse.
Where are you testing?
To check the circuit like I said in Post 11 you need the relay, blower and A/C fuse unplugged, the relay is kind of a bear to unplug but enough wiggling will get it out.

 

Ok - probably best to plug into one of the 12v receptacles or connect to the cable going to them. A seat heater must draw a considerable amount of current.

Re: the OP's situation - automotive relays I've seen are typically sealed. Others I've worked have clear covers that can be removed to access the contacts but in this situation that wouldn't be relevant. I've never seen a shorted relay coil. I've seen relays get stuck closed after power is withdrawn if there's too much current draw where the contacts actually fuse together. As mentioned, need to have the relay, blower and A/C fuse unplugged.

 

Not sure, I would imagine 5-15 amps for a heating circuit.

The cover on many automotive relays can be removed pretty easily but some are sealed and can't be taken apart.
I've seen relay contacts get stuck as well as burned where they don't make connection as well as control coils go open circuit but I've never had a relay be the cause of a blown fuse.

 

I can tell you that the 2015 diagrams show that the OEM seat heaters are run off of a 30A fuse.
Does that say much? Not really, unless you’re using OEM heaters.

Your assumption of 10-15A seems correct for PER seat


Basically, I’m reconfirming your prior statement.
“I don’t know of any wires/circuits that large in the cab, that I’d want to tap into”.

 

I feel really dumb... I thought the relay was good but it wasn't. I bought a new relay and a new 50 amp fuse and it's working like a charm. I thank all you guys out there for your support and help. It really means a lot. I'll definitely start coming to you guys for any of my help from now on

 

Very interesting, the contacts must have somehow been shorting to pin 4 and 5 at the same time. Glad you got it fixed

 

Thanks @Dm93 You've been a great help through my troubleshooting journey and you were right, if I would have been smart enough to get a teslot before I replace the blower and resistor and started testing things I would have figured that out a lot sooner lol ‍♂️ but you have been a big help and I appreciate it a lot. I don't have to go to work in a cold vehicle now