Intermittant Blower motor and A/C

[HellCreek]

Has anyone run into this problem before and come up with a solution?  I turn on my A/C  with the blower on high and everything works correctly.  After about 10 to 15 minutes of driving the blower shuts off and also the A/C compressor.  Note: I have a 2.5L engine, so I can tell if the compressor is running or not.  Then after a little while everything turns back on and all is good - for a little while more, then it happen again.  When the system runs, the air is cold, and I have just had the system recharged professionally with no leaks reported.  It acts like there is a circuit breaker in the wiring, but the diagram doesn't show one.  Any ideas?

[eaglescout526]

There is a breaker like thing, it’s a thermistor and it’s set to make sure the evap doesn’t freeze over….I should unplug mine for AZ honestly. But if both the blower motor and compressor are turning off together, something is wrong somewhere. Or something is getting heat soaked and causing power loss IE the blower control switch on the AC deck. 
I’ve also had a relay die from heat soaking and stop the compressor. 

[HellCreek]

I have taken the dash apart and checked the A/C controller.  The wires and connectors were in good shape - not burned.  I took the switches apart (you can do that if you are careful) and cleaned them and re-greased them with dielectric grease.  I bought a new blower motor resistor because it has a thermistor, but I haven't installed it yet.  I also checked the low pressure switch and installed new connectors on the wires, since they were not making good contact with the switch.  I can't figure out why the blower motor would shut down with the compressor, since it doesn't come back on when I change the setting to vent or heat.  As I said, it comes back on by itself and then shuts off and on like a circuit breaker resetting itself.

[eaglescout526]

Factory set up or dealer installed?

[Ωhm]

The Blower Fuse (25Amp) is common to both the Blower Motor and the AC clutch. When problem exist do you lose other things like Wipers, Turn Signals or Radio or maybe all three (3) at once?

[zomeizter]

I recently had the issue you describe, the problem was the blower fuse got hot and the plastic melted and deformed causing the fan to work intermittently. I replaced the fuse and cleaned and tightened the fuse contacts on the fuse block, all is well now.

[HellCreek]

This is a factory installed A/C.  I will check the blower fuse, thanks.  I also hear a relay click on and off when this happens.  The relay must be near the firewall, since I can hear it while I am driving.  Also on these 2.5L engines, I believe there is a vacuum cutoff that allows more power when accelerating.  My A/C always goes off when I pass or climb a hill.

[eaglescout526]

54 minutes ago, HellCreek said:

I believe there is a vacuum cutoff that allows more power when accelerating.  My A/C always goes off when I pass or climb a hill.

This is correct. Combined with power steering, it will shut off AC to compensate for acceleration.  

[cruiser54]

Does your radio cut out or turn signals quit working when the AC cuts out? 

[HellCreek]

Hi, Cruiser54,

 

I'm not sure.  I don't play the radio very much, and it usually goes out when I am on the highway, so I am not using my turn signals.  Next time this happens, I will try to activate them.  The A/C works normally for a while then cuts off after a few miles.  Like I said earlier, it acts like a circuit breaker has tripped, although at times it comes back on right away - too soon for a breaker to reset, and sometimes it stays off for several miles (or minutes).  With a 2.5L I can tell when it cuts off and back on, and I hear the relay click when it does both.  The duration of the on-off cycle is random.

 

Thanks,

Tom

[cruiser54]

That^^ is why I ask. 

If the radio cuts out and turn signals don't work during "failure mode", it could be the ignition switch.

 

 

[HellCreek]

That very well could be it.  I changed the blower resistor block thinking the thermistor could be the issue with no change in the problem.  I have routinely turned the ignition key counter-clockwise after starting the truck because the spring does not return it to allow the accessories or gauges to run, but I have done that since I owned the truck in 2005.  Also, when the problem occurs, the gauges still work, and I have confirmed that the radio does not shut off.  The on-off problem also happens quicker with the A/C on "Max" then it does on "Norm."  I have also confirmed that there is a 30 amp breaker where the blower fuse should go.  I'm thinking that something is drawing too many amps.  I might add that the blower has been replaced.

[cruiser54]

CRUISER'S MOSTLY RENIX TIPS

IMPROVING BLOWER MOTOR PERFORMANCE

NOVEMBER 28, 2015 CRUISER54 30 COMMENTS

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. 

[HellCreek]

Hi, Cruiser,

 

I will do that.  I have already done all of the other "Renix Tips".  I have also noticed that the volt meter only registers about 10 volts max.  When the lights are on or the blower is running, it drops to about 8 volts.  I have had the  alternator checked and did all of the "Renix Tips", especially the grounds.  I might add that it has always performed in this manner, and I think that the volt meter is out of calibration or just bad.  This is not the original gauge cluster because I replaced it with a full-gauge cluster shortly after I bought the truck.

[HellCreek]

Hi, Cruiser,

 

I refreshed the ground on the left fender under the washer fluid bottle.  I also made a new blower ground per your instructions on the right fender.  There was no change in the intermittent blower problem.  It acts like a circuit breaker, as I said, or a loose connection - sometimes it stays on for a while, and sometimes it just goes on and off like flipping a switch or just stays off for a while.  I also thought that by refreshing the ground the volt meter performance would be improved, but it wasn't.  Do you have any suggestions?

 

Thanks,

Tom

[eaglescout526]

Mind posting some pics of the engine bay and the area above the passenger floor? I’m curious if you have a dealer installed set up or a factory set up. 

[Manche757]

I had the same thing happen.   It would go out then come back on by itself.  The mechanic who installed the ac finally removed the ac from the fuse block and put it on its own fuse.  It might seem like a tea leaf solution but I never had that problem again.  

[HellCreek]

1 hour ago, eaglescout526 said:

Mind posting some pics of the engine bay and the area above the passenger floor? I’m curious if you have a dealer installed set up or a factory set up. 

I can take pictures with my phone, but I don't know how to get them to my computer.  This definitely looks to be a factory installed A/C, though.  The firewall holes (pass throughs) all have rolled edges. 

 

On 8/16/2023 at 7:08 AM, cruiser54 said:

Does your radio cut out or turn signals quit working when the AC cuts out? 

I have confirmed that the only things that stop working are the A/C clutch and the blower.  Lights, turn signals, radio, gauges all work when the A/C cuts out.

 

I have by-passed the low pressure switch with a jumper and eliminated that as a cause. 

[eaglescout526]

7 minutes ago, HellCreek said:

I can take pictures with my phone, but I don't know how to get them to my computer.  This definitely looks to be a factory installed A/C, though.  The firewall holes (pass throughs) all have rolled edges.

You can post pics from your phone. Or you can plug your phone into the computer and get them off that way or the best way I have found is to use OneDrive 

[HellCreek]

On 8/15/2023 at 1:18 PM, eaglescout526 said:

This is correct. Combined with power steering, it will shut off AC to compensate for acceleration.  

Where is the vacuum switch located?  I want to check that.  Also, how can you tell if the A/C is factory installed or dealer installed by looking at it?

[HellCreek]

While the problem was occurring, I switched the A/C control to "Vent" and the blower was still intermittent, which leads me to believe that the problem is with the blower or its wiring.

[eaglescout526]

2 hours ago, HellCreek said:

Where is the vacuum switch located?  I want to check that.  Also, how can you tell if the A/C is factory installed or dealer installed by looking at it?

It’s not a vacuum switch it’s a load switch. The ECU internally will switch off the compressor during acceleration but does not control the blower motor. 
 

Easy, the dealer set up uses a lot more wiring(mounted on the air box)and relays than the factory set up. The factory set up is integrated into the harness with no extra wiring. Oh and the mounting brackets would be different. It just depends on what was available or the belt set up. 

[Ωhm]

Backprobe AC Mode SW (C236). Backprobe connector C236_D (VIO/YEL) using voltmeter or testlight. Connect other end to good ground. Look for voltage drop out when problem occurs.

 

 

 

 

[HellCreek]

On 8/23/2023 at 2:02 PM, eaglescout526 said:

It’s not a vacuum switch it’s a load switch. The ECU internally will switch off the compressor during acceleration but does not control the blower motor. 
 

Easy, the dealer set up uses a lot more wiring(mounted on the air box)and relays than the factory set up. The factory set up is integrated into the harness with no extra wiring. Oh and the mounting brackets would be different. It just depends on what was available or the belt set up. 

This must be a factory setup.  All of the wires are behind the dash.  I would have to take the entire dash panel out of the truck in order to get to the wiring.  The only wires visible are the ones going to the blower resistor and thermostat.

 

On 8/23/2023 at 3:52 PM, Ωhm said:

Backprobe AC Mode SW (C236). Backprobe connector C236_D (VIO/YEL) using voltmeter or testlight. Connect other end to good ground. Look for voltage drop out when problem occurs.

 

 

 

 

I have to remove the radio and/or the A/C mode switch to get to this.

 

I replaced the blower motor and relay (on the right fender well behind the coil) today and took it for a test drive.  The problem persists.  I checked the 30 amp circuit breaker (where the blower fuse normally is) and it was hot enough to burn my fingers.  Something is drawing way too many amps.  None of the wires that I could get to under the hood were hot, so it must be something under the dash.  

[HellCreek]

I just finished a test run with the blower on only with the selector set on Vent.  Everything worked as it should, and when I finished I touched the blower circuit breaker, and it was not even warm.  Evidently, the blower circuit is o.k.  It is only when I switch the selector to A/C that the problem occurs and the breaker gets hot.  Any suggestions?