Blower Fuse Melting After Recharging A/C [1989 Jeep Comanche 4.0 I6]

[james-mc]

Hello everyone. Well I have found my next problem on this ol jeep. 

Yesterday I recharged the A/C system and after letting it run on Max AC with the blower on high I noticed a burning smell. Turns out the 25a blower fuse was melting. I'm wondering where to start looking. I first thought maybe the fuse terminal contacts were creating some heat as they were a little loose and dirty. I tried cleaning them the best I could and used precision needle nose to pinch them back together. 

 

I let the AC run for about 10 minutes and checked the fuse. It was hot to the touch. So I'm thinking it has to have something to do with the AC clutch engaging but I'm not sure.

 

When I was flushing / burping the coolant I had let the blower motor run for a solid 25 or 30 minutes and it never melted the fuse or even allowed the fuse to heat up. 

 

Any suggestions on what I should check next?

[ghetdjc320]

Have you done Cruisers tips with the blower motor ground? Perhaps give that a shot if you haven’t. Does your blower motor have the provision for the AC vent hose to cool it?

[james-mc]

On 5/16/2021 at 1:41 AM, ghetdjc320 said:

Have you done Cruisers tips with the blower motor ground? Perhaps give that a shot if you haven’t. Does your blower motor have the provision for the AC vent hose to cool it?

I have not. the only thing I've done with the grounds was pull them off, scrape the Paint, clean the eyelets, and put them back on. I bought the stuff to run another ground from the blower motor to the engine compartment. The blower motor does have a spot for some sort of vent hose that goes in the bottom. And I do have a new blower motor in the garage. I didn't put it on yet because it was a loose fuse causing the blower motor not to work when I got the truck

[cruiser54]

CRUISER'S MOSTLY RENIX TIPS

IMPROVING BLOWER MOTOR PERFORMANCE

NOVEMBER 28, 2015 CRUISER54 28 COMMENTS EDIT

On 1984 to 1990 MJs and XJs, the blower motor’s factory grounding point is on the driver side inner fender under the sheet metal screw. This ground is shared with windshield wipers, front windshield washers, rear windshield washers, AC clutch relay, fan control relay, fog lamps, fan motor, headlamps, front turn signals, front side markers, and park lamps.

So your blower motor has its ground point 10 feet away from where it is located!!

What we’re going to do is leave that ground intact and also ground the blower motor on the passenger side inner fender much closer to the blower motor itself. This will also benefit the other components on the factory ground circuit. Take this opportunity to refresh the factory ground as a matter of course. Remove the screw, scrape the surface to bare metal and reinstall the screw securely.

Here’s what I do to get the ground much closer to the blower motor and add another ground point to this overloaded ground circuit.

Find the blower motor connector on the passenger side. Red and Black two wire connector.

Find a location where the black wire can be made to reach the passenger side inner fender, and cut the wire. You may have to do some rerouting of the harness to achieve this.

Take both cut pieces of wire and put them together into a yellow eyelet and crimp. Fasten the eyelet to a place on the passenger side inner fender with a sheet metal screw after applying OxGard to the contact surfaces. Be sure to scrape the attaching point on the fender to bare metal first.

Your blower motor will now turn faster and last longer, and the other electrical components on the circuit will benefit from a better ground path. 

[james-mc]

Thanks Cruiser I will have to do that. Sorry for the late reply. I thought I was following this post but wasnt. Ill gather the supplies I need this weekend and will give that a try. I might also just go ahead and install the new blower motor while I'm at. The past week ive been trying to find a compatible speedometer cable as the one oreillys gave me doesnt engage my speedo.

[cruiser54]

Better get that done. No need to melt wires and stuff. 

What kind of cable end do you have at the speedo? 

[james-mc]

1 hour ago, cruiser54 said:

Better get that done. No need to melt wires and stuff. 

What kind of cable end do you have at the speedo? 

Its a plastic clip. I finally got new one to stay on the speedo. The one oreillys sold me i had to really sink it on there and then slide the retaining clip forward for it to work. Speedo still bounces but not as bad. I had to replace it because the cable housing on my old one was deteriorating and the clip broke off at the cable housing. But i think this one should work. It is longer but i ran it back to the gear on the trans and zip tied it along the way. I tried my best to make sure there wasn't too tight bends on it. 

 

The new one is a CA3068 https://www.oreillyauto.com/detail/c/pioneer-inc/engine-parts---mounts/transmission---transaxle/transmission-parts/speedometer-cable/d60839b9f204/pioneer-inc-speedometer-cable/pio0/ca3068/v/a/2224/automotive-suv-1989-jeep-cherokee

 

[james-mc]

Also as far as ground refreshing I gave it a try with the parts I had on hand. I had everything except for the oxguard. Also i tried to clean some more gunk from terminals with a q-tip and some iso alcohol.

 

After about 20-25 minutes on MAX AC it didnt melt the fuse. However when I pulled the blower fuse it was hot to the touch, almost on the verge of melting. Not too much longer and I think it would have melted. I haven't been running the AC or the blower motor at all when driving because I don't want this jeep to burn to the ground lol.

[james-mc]

I think eventually I'm going to have to pull the fuse box and replace some dirty and corroded terminals. The P.O. had a master cylinder leak that dripped some brake fluid on the fuse box. I sent quite some time trying to clean the corrosion and residue but I think I might be ahead to replace some of the nastier terminals. I bet there is still some gunk in between the terminals I can't get.

[cruiser54]

Added the ground to the blower motor?

You're doing all the right things!!

[james-mc]

20 hours ago, cruiser54 said:

Added the ground to the blower motor?

You're doing all the right things!!

Yep. I made sure to scrape the paint and i use the course wire brush to clean the screw and contact point. I'm beginning to wonder if maybe the ac clutch is drawing too much current. I might try adding some pag oil to the system. GF ran the defrost this morning on way to work (25 mi) and it didnt melt or begin to melt the fuse. This leads me to believe that it may have something to do with the AC compressor clutch itself.

[Ωhm]

When AC compressor clutch is engaged, make sure you have battery voltage (B+) on D2_6. If you can also check this using a testlight, looking for brightly lit. Same as if you put the testlight across the battery terminals.