2016 Peterbilt 587 Electrical problems

[Waterloo]

(03-15-2021 )Alexp86 Wrote:  Still trying to figure out the issue I'm having. I've spent a long time looking through wire cleaning grounds etc...

The biggest issue for me atm is the a/c defroster not working. When I click the snow flake to turn the cold air on or if I put it on defrost its popping the fuse.

I've unplugged the compressor and it still pops when I click that snowflake, so I unplugged the high and low pressure switch and it didint pop. If I plug 1 in it doesnt pop but with both switches plugged in it pops.
Does anyone know what could be causing this? I had a friend tell me it's the computer that will need to be replaced and I'll be looking at 5000+ is this true?

I would look at the blend door actuator, it will be up under the dash, passenger side, on the left side of the AC condenser box, toward the steering wheel side, there are normally two. Also, there is more than likely one under the hood at the firewall, up under the cowl on the right side of the AC condenser/box unit. I would start under the hood, that is the fresh air blend door actuator and is normally a different part number than what is under the dash. When you go to defrost, closing that fresh air blend door is the first one to go into action to cut off the fresh air coming into the cab. Does the AC have issues when you put it at MAX? Or only at defrost? If only defrost, I would suspect the interior unit, it will be the actuator at the top of your AC condenser box, a real PIA to get too, but it is doable. The screws they use to hold those in are torx heads, a ratchet able to hold a torx bit, or a torx bit socket, is the best tool to use to get these out. I want to say it is a size 15 torx bit, but not 100% sure on that.

My thinking, it is a wiring issue, rubbing up against something metal blowing the fuse. You will need to pull all of the plastic crap off of the dash from the floor up on the passenger side to get to it.

Here is a link to the blend door actuators, https://truckerac.com/heaterandactuators.html

Just a tip, if one blend door actuator fails under the dash, odds are the other is soon to follow, I always replace both when one fails. The one under the hood, I have never had to replace it, going on 1.2 million miles... The ones under the dash and sleeper, every couple of years they tend to fail. I normally carry a spare with me, as the dash and sleeper actuators are normally the same part number.

[Alexp86]

(03-16-2021 )Waterloo Wrote:  

(03-15-2021 )Alexp86 Wrote:  Still trying to figure out the issue I'm having. I've spent a long time looking through wire cleaning grounds etc...

The biggest issue for me atm is the a/c defroster not working. When I click the snow flake to turn the cold air on or if I put it on defrost its popping the fuse.

I've unplugged the compressor and it still pops when I click that snowflake, so I unplugged the high and low pressure switch and it didint pop. If I plug 1 in it doesnt pop but with both switches plugged in it pops.
Does anyone know what could be causing this? I had a friend tell me it's the computer that will need to be replaced and I'll be looking at 5000+ is this true?

I would look at the blend door actuator, it will be up under the dash, passenger side, on the left side of the AC condenser box, toward the steering wheel side, there are normally two. Also, there is more than likely one under the hood at the firewall, up under the cowl on the right side of the AC condenser/box unit. I would start under the hood, that is the fresh air blend door actuator and is normally a different part number than what is under the dash. When you go to defrost, closing that fresh air blend door is the first one to go into action to cut off the fresh air coming into the cab. Does the AC have issues when you put it at MAX? Or only at defrost? If only defrost, I would suspect the interior unit, it will be the actuator at the top of your AC condenser box, a real PIA to get too, but it is doable. The screws they use to hold those in are torx heads, a ratchet able to hold a torx bit, or a torx bit socket, is the best tool to use to get these out. I want to say it is a size 15 torx bit, but not 100% sure on that.

My thinking, it is a wiring issue, rubbing up against something metal blowing the fuse. You will need to pull all of the plastic crap off of the dash from the floor up on the passenger side to get to it.

Here is a link to the blend door actuators, https://truckerac.com/heaterandactuators.html

Just a tip, if one blend door actuator fails under the dash, odds are the other is soon to follow, I always replace both when one fails. The one under the hood, I have never had to replace it, going on 1.2 million miles... The ones under the dash and sleeper, every couple of years they tend to fail. I normally carry a spare with me, as the dash and sleeper actuators are normally the same part number.

I have been feeling air when I'm driving and the fan is in the off position.
The fuse has been blowing with the a/c max cold on or in the defrost setting.
I will get tonight as soon as I stop for the day
Thank you so much!

[Nilao]

I don't have wiring diagrams and usually don't need them. Common sense and a basic understanding of electrical systems would get you far. If it only blows the fuse when you press the AC on button then it's the wire from the fuse to the compressor. Not the computer. You say it only blows if both limit switches are plugged in. I'd expect the wire after the limit switches to the compressor as I believe the compressor energize wire runs from the AC clutch relay into the low limit then into the high limit and then to the compressor on most peterbilts.

Funny story on abs lights.. I have a friend who has since retired that was always complaining the inside edges of all.4 wheel ends were cupping and his abs light would come on turning corners. I told him his wheel bearings are loose and they need to be checked. He fought this condition for a couple years. Took it to 2 different shops to have new drives put on and check the bearings. Then he blew a wheel seal a few hundred miles from my house. Long story short we found all 4 wheel ends were loose, so loose I disassembled all 4 by hand without a ratchet to release the lock nuts in the hubs. These "trained" techs couldn't be bothered to read the plastic yellow ring around the locking ring that said LMS hub, special torquing required. I asked if they had ever put a 300 ftlb torque wrench on it and he said no they tightened it and backed it off. I let him know they cost him 3 spindles and hubs. The 4th was still serviceable.

So in a nut she'll...don't trust shops.

[Alexp86]

(03-17-2021 )Nilao Wrote:  I don't have wiring diagrams and usually don't need them. Common sense and a basic understanding of electrical systems would get you far. If it only blows the fuse when you press the AC on button then it's the wire from the fuse to the compressor. Not the computer. You say it only blows if both limit switches are plugged in. I'd expect the wire after the limit switches to the compressor as I believe the compressor energize wire runs from the AC clutch relay into the low limit then into the high limit and then to the compressor on most peterbilts.

Funny story on abs lights.. I have a friend who has since retired that was always complaining the inside edges of all.4 wheel ends were cupping and his abs light would come on turning corners. I told him his wheel bearings are loose and they need to be checked. He fought this condition for a couple years. Took it to 2 different shops to have new drives put on and check the bearings. Then he blew a wheel seal a few hundred miles from my house. Long story short we found all 4 wheel ends were loose, so loose I disassembled all 4 by hand without a ratchet to release the lock nuts in the hubs. These "trained" techs couldn't be bothered to read the plastic yellow ring around the locking ring that said LMS hub, special torquing required. I asked if they had ever put a 300 ftlb torque wrench on it and he said no they tightened it and backed it off. I let him know they cost him 3 spindles and hubs. The 4th was still serviceable.

So in a nut she'll...don't trust shops.

I went for an oil change at the TA n noticed the sign said they did electrical and being my ac would not stay on I asked the guy how much he would charge me to attempt to diag this issue he told me 40 bucks so I said why not..
He spent about 2 hours trying to figure it out he got a master mechanic on video and the guy had him unplug the compressor and the fuse still blew then he took apart the blower assembly and tried to follow the high switch wires that went through the assembly towards the cab but was unable to reach in there through the blower so he went to the fuse panel and tried changing the relay with a new one he had and it still blew.
He then got a peterbilt mechanic on his video chat the guy told him to do the same thing the first guy told him to do unplug the compressor etc.. in the end he ended up telling him that I needed a new compressor, after he got off the phone he said unfortunately I can't help you I don't believe its the compressor though. He said that I may have a wire that's broken in the cab most likely the high pressure switch wire he couldnt reach, he said I would have to take my whole dash apart.
I haven't been able to get all the panels off because I'm on the road and have loads to deliver and very little time until the 26th, when I get home I'll be taking everything apart and trying to find this wire and also check the blend door actuators like Waterloo suggested.
Peterbilt said they will print me the wiring diagram so I'll be getting that when I get home, not sure what good it'll do being I ha e no idea on how to read it. I'll be watching some YouTube videos on it.

The rear temp sensor that keeps failing I followed the wire to a clip that was zip tied behind a bunch of other wires removed the protective cover, cleaned it really good, repositioned it and and it hasn't tripped it since, but it looks very old and worn out So I'll be replacing that when I get back.

The abs, its the trailer abs light that would come on on my dash when I made a turn or hit a pothole, I ended up using a flat head to spread the prongs on the pig tail and it stopped coming on for a few days but now the trailer abs is just on, on my dash but not the trailer even if I unhook from the trailer the trailer abs stays on.

I'll be taking it to a shop to get the bearings checked n re torqued just in case it's loose. I will watch them do it so I can feel comfortable enough to do it myself next time.

[Alexp86]

I replaced my gladhand seals and as soon as I started driving the trailer abs went off hopefully that's what was wrong with that.