Blower motor wire routing thru firewall

[TrueTexas]

Does anyone know where the two wires (positive and negative) exit the firewall to go to the blower motor?
The ones I am asking about are the ones that connect directly to the blower motor. It seems like they pass above the heater box but I lose them there. Thinking of redoing the negative from my relay setup and then bringing a positive direct from the battery with some larger gauge wire (8 or 10 gauge)

I'm still chasing hot wires at the positive relay and have rewired it with a 80/60 amp relay. This made it better but the relays and wire connections are still pretty warm to the touch.

BTW - I am on my second new Mopar blower motor. Both are pulling 23-24 amps on high. Could be a crappy DC ammeter but a lousy ammeter doesn't explain the wires getting hot.

 

[GEEP4ME]

It doesn't really exit the firewall. It comes down between the heater case and the firewall. The blower motor sets back a little from the firewall. The wires come down on the interior side of the firewall.

 

[TrueTexas]

Thanks @GEEP4ME that is gonna make it much easier. Do you know if you can buy a connector for the blower motor? I haven't been able to figure out if anyone sells one. If not, I guess some spade terminals would work.

 

[GEEP4ME]

I don't believe there is one. I think you have to replace the harness, or find a used one to splice in.

 

[TJ Hunnicutt]

The fuse for the blower motor is only 10 Amps so you shouldn't be getting that kind of current. Is your fuse still 10A?

If your wires are getting hot and the current pull is normal, you probably have a bad connection...which will cause the wires around that connection to be hot simply due to the heat from the bad connection traveling down the copper wire. If your wires are getting hot nowhere near a connector, you are actually pulling much current or your wires are severely corroded (which would generally require that they sit in water, at an end, long enough to wick up into the wire...pretty unlikely).

 

[TrueTexas]

@TJ Hunnicutt The 10 amp fuse (in the fuse box behind the glove compartment) is for the coil of the relay that switches on the 12v+ wire for the blower motor. The 12v+ wire that feeds the fan is located in spot 11 in the underhood fuse box. It is 40 amps. I'm sure it is oversized to handle the tip in current when first turning on the fan.

I've been thru the majority of the wiring on the fans and have built a relay array to remove any high current from the switches. Both of the new in box Mopar fans I bought showed 23/24 amps of draw but I was using a cheap Amazon Ammeter with DC current capability so its possible the reading was wrong.

I do agree that heat at the connectors would indicate a bad connection or high resistance at the connection. I have cut out the factory relay harness and crimped new terminals on. The wires were clean (no corrosion). They were also crimped properly using the same Klein crimpers I have used for 25+ years and I only used high quality terminals. They are definitely better than with the factory relay harness but still getting hot after a few minutes of use. Too hot for me to feel comfortable running the fan for an extended period of time.

 

[TJ Hunnicutt]

Sorry, misread (I do that sometimes).
Hmmm...I'll cogitate on why the wires may still be getting hot and let you know if I cogetize anything

 

[TJ Hunnicutt]

Did you see any signs of someone before you messing with the wiring for this circuit, like maybe replacing the wire with something smaller than factory? For a 30-40 amp circuit you would want at least 8 gauge, preferably 6 (assuming Chrysler followed standards).
Are you reading the current at the relay where it is getting hot? Just making sure you are getting a reading of the total current in that wire.

 

[TrueTexas]

I bought the TJ from a friend, who was the original owner. The blower motor wiring was a mess, he actually had bypassed the 12v+ relay, the blower motor resistor was shot, and the 3 wire harness into the switch was melted.
I orignally corrected all of that mess with new connectors. But the wires were all orignal

The Mopar wiring is still stock and the reason I was going to direct wire the blower motor is that the largest wire that Chrysler used is 12 gauge. Way too undersized to carry the current necessary in my humble opinion. My thought is very similar to yours, I was going to bring in a 8 or 10 gauge 12v+ wire direct to the blower motor and wire a new single piece of 10 gauge from my relay setup for the ground.

In the relay bypass I built, I used automotive grade 12 gauge copper to rewire the grounds, a new Dorman blower resistor wiring harness (also 12 gauge) and even used 12 gauge for all of the low current signal wires. So almost all of the wiring is now new, except for the 12V+ side, and the last foot or so from the 12v- to the blower motor.

I just went and checked my connections to the 12v+ relay, super tight and the relay even has .375" spade connectors on it.

 

[TJ Hunnicutt]

Wow! Any clue what caused the original meltdown? I'd hate to think you still had the original issue, whatever it was, still lurking around.
If you unplug the blower, does your current reading go to zero or is there something else pulling juice through that circuit?

Funny, I've never even checked the gauge in any of the OE wiring. Not surprising though; I'm sure they went with the smallest that would do...copper's expensive stuff.

 

[TrueTexas]

Its ironic that when these things were built, copper was still pretty cheap. Yet, they still decided to cheap out on the electrical systems. I believe the original issues were related to the fan and the PO said that he never replaced it. Judging by what was left of the label, I am inclined to agree that it was the original. So I guess it was just damage on top of damage that he tried to fix MacGyver style along the way.

Seems like the wiring is a common HVAC electrical issues as my other TJ has issues with the wiring as well, just haven't gotten to messing with that one yet. Good thing I now have 2 new blower motors so it isn't a complete waste of $$$

Yeah, if unplug the blower motor or check current with it off, I have zero current running thru the wiring so nothing else is hanging off the circuit.

 

[TJ Hunnicutt]

Did a little searching. Here's a thread from that other forum that actually mentions some amp draw numbers and they are all way lower than you're seeing. https://Wrangler Forum/threads/blower-motor-info.1605569/ Keep in mind that he was bench-testing it so the load on the motor was minimal.

 

[TrueTexas]

The link isn't working for me but I am guessing it was the same thread that I saw that led me to believe the first motor I bought had an issue when my cheap meter read 23.6 amps and hot wires. After buying the second motor and swapping it, I got virtually the same readings (24.2 amps) and still had hot wires.
That one made me think the meter was to blame so I rewired the relay with an 80amp relay.

Interesting note. With vehicle running at getting about 14 volts, current is 24 amps. With vehicle off at 12.6 volts, current draw was a hair over 20 amps. So bench testing at 12v could be about 18amps on these motors, relatively in line with expected draw.

Since the wires are still heating ( albeit not as much as before) with the new relay, I have now been thinking that direct wiring the positive with a larger gauge wire and keeping the negative running thru the relays was the last thing left in the circuit to try

Of course it is possible to get 2 bad motors but what are the odds?

Btw- here is a pic of my relay setup on the ground side of the circuit

 

[TJ Hunnicutt]

...Btw- here is a pic of my relay setup on the ground side of the circuit

View attachment 177191

View attachment 177192

View attachment 177190

Nice work! I see you're type "A"...I respect that

 

[TrueTexas]

Haha definitely type A. Ive spent 1.5 years re-building this Jeep in my spare time. Mopar parts where I could get them. I am 99% done, just finished replacing the windsheild, BedRug and Caltrend seat covers this week.Ready to go get it inspected and renew the registration.

Only have this pesky blower motor problem left to deal with.

 

[TrueTexas]

Wanted to follow up on this...

I have essentially replaced 90% of the wiring for the blower motor circuit.

For the 12v+, I ran a 10 gauge wire from the fuse box thru a new fuse and directly to the relay behind the glove box. I used a 70 Amp relay made by Song Chuan that I bought from Mouser Electric. I then wired a new 10 gauge final lead to the new Mopar Blower Motor.

For the 12v- side, I also swapped out the 40amp Online LED Store Amazon relays for some 50 Amp Song Chuan relays (also from Mouser) and a new 10 gauge negative wire from my relays to the blower motor.

This has solved my wiring issues. Relays and wire no longer get hot and everything seems to be working perfectly.

Key to the relay mod. Use high quality relays rated for continuous use and replace the old tired wiring with some quality pure copper wire. I was seeing about a 4 volt drop at the motor before replacing wiring and now I am seeing about a 0.2 volt drop.

 

[TJ Hunnicutt]

Wanted to follow up on this...

I have essentially replaced 90% of the wiring for the blower motor circuit.

For the 12v+, I ran a 10 gauge wire from the fuse box thru a new fuse and directly to the relay behind the glove box. I used a 70 Amp relay made by Song Chuan that I bought from Mouser Electric. I then wired a new 10 gauge final lead to the new Mopar Blower Motor.

For the 12v- side, I also swapped out the 40amp Online LED Store Amazon relays for some 50 Amp Song Chuan relays (also from Mouser) and a new 10 gauge negative wire from my relays to the blower motor.

This has solved my wiring issues. Relays and wire no longer get hot and everything seems to be working perfectly.

Key to the relay mod. Use high quality relays rated for continuous use and replace the old tired wiring with some quality pure copper wire. I was seeing about a 4 volt drop at the motor before replacing wiring and now I am seeing about a 0.2 volt drop.

View attachment 191009

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Nice work!