Yaesu: Odd FT-891 Issue with F-150

KB4MSZ

Billy
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Ok, it has been long enough for an evaluation of my odd situation with my 2018 F-150 and my FT-891.

First, a little history. My previous truck was a 2003 F-150. My FT-891 worked just fine in that truck for 3 years. I purchased the 2018 truck in June of 2021, and soon installed all of my equipment (FT-891, FT-8900, FT5DR HT, President Mckinley CB). All are ran off the truck power, same as they did in the 2003 truck.

After about 3 months I noticed that the receive in my FT-891 was very weak. A few days later it was gone entirely. The transmitter seemed to still work properly. I uninstalled the FT-891, boxed it up and sent it to California. Not wanting to be without the HF ham bands I made my first trip to the new Winter Springs HRO store and bought a new one. Installation was easy enough; everything was already in place.

The older radio returned fully repaired about 5 weeks later and now I had two of the little monsters to play with. Except that about 3 months later the new radio came down with the same issue, receiver completely dead.

With this happening to yet another of the exact same model, I figured there must be something about the installation that was causing the problem. None of the other radios had any issues.

So, I re-installed the original FT-891 and sent the new one in for service. The same cycle occurred, and in about 6 weeks I had the new radio back (covered under warranty this time). About a month later I was heading out to do some portable operating at a local park in south Tampa. I turned the radio on as I left home and all seemed fine, I was listening to 20 meters with plenty of receive sensitivity. On the way to the park, I went through a drive-through to get a drink, turning down the volume on the radio so that I could order and interact with the two drive-through window people. I was most of the way to the park and turned the volume back up. No receive! It was dead again! I got to thinking about this and came up with the idea that maybe there was an issue with my hamstick antenna hitting the drive-through canopy and receiving something the radio didn’t like. This made sense, I often went through this drive-through before going to the park.

Back goes the older radio to California. Before installing the newer one I put in an antenna switch that I could use to take the antenna off of the radio whenever I went through drive-throughs. All went well for a few months and the older radio came back repaired.

One morning I was headed to work and went through a drive-through for some coffee. I turned the antenna off at the switch before entering, got my coffee, and headed back out to work. When I switched the antenna back on there was no receive! It was as dead as Mozart. So much for the antenna idea. Off goes the radio for repair. The local FedEx office now has a counter set up for me 😊

Back to brainstorming. One thing I noticed with this radio is a “clicking” that it makes while I am driving. I have a voltage monitor connected to my gear, and I also noticed that the voltage of the truck varies considerably due to the BMS system. It seemed that these voltage changes (they happen quickly) are when the radio makes its clicking sound. I got online and found out how to disable the BMS system altogether, it simply requires unplugging the connector that attaches to the negative side of the battery. No more clicking radio. As a bonus, this also disables Auto-Start-Stop. I always turned Auto-Start off manually, but now I don’t have to bother with it. I never start the truck when the radio is on.

Back in went the older radio in mid-February, and all has been fine since. It has been almost 7 months and no more issues. Does anyone else have any experience with the BMS system like I have?

I have attached a screen capture of one of the repair tickets, all of them have been the same. Hopefully no one else is having this issue, but maybe this information will help if they are.

1725215537708.png
 

KF0NYL

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Oct 20, 2023
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How to you have the power connected? I didn't see that mentioned in your post.

While I do not have an HF radio in my 2023 Ford Escape, I do have dual band 2m/70cm and GMRS radios installed. I ran the positive wires directly to the positive battery terminal and the negative wires directly to a chassis ground.
 

KB4MSZ

Billy
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Tampa, Florida
The setup is the same as you described. The ground is inside the dashboard. I have a braded ground "pigtail" that comes out at the bottom of the center faceplate of the dashboard. All of the radio equipment grounds to that point. 7 months and no problems so far with the BMS system disabled. One point I forgot to mention in my first post is that I do not transmit with any other HF radios while the FT-891 is on. I have used the FT-8900 while I was parked with the engine off, and for extended periods of time such as at a park, but without problems.
 

robertmac

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What does the Ford Factory Manual state about connecting auxiliary radio systems. That's how I learned not to connect to neg terminal. Not sure if anything new with a 2018.
 

mmckenna

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What does the Ford Factory Manual state about connecting auxiliary radio systems. That's how I learned not to connect to neg terminal. Not sure if anything new with a 2018.

I had a 2018 F-350. The Ford guides were pretty clear on it. Positive to positive battery, negative to body ground.
Mine was Diesel, so no auto start/stop. I was running various LMR radios, Motorola CDM and eventually a Harris XL-200M.
Never had any issues with those radios. Radios were power 100% of the time and used the ignition sense lead to trigger the power. Never turned them off when starting.

Currently have a 2024 Chevy Silverado (half ton) and it does have the auto start/stop feature. Harris XL-200M in it, powered direct off battery with ignition switch control. Never had any issues.


Billy's experience seems to suggest the start stop feature was contributing to the issue. I'd probably want to see what the voltage did when it started.
 

devicelab

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It does appear to be a failing diode in the Rx chain of the receiver. The diode is pretty generic but really only appears on the Rx side of the MAIN board. (There are too many to know for certain.)

Very valid presumption that a voltage spike is blowing the diode in the Rx chain.
 

KB4MSZ

Billy
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Billy's experience seems to suggest the start stop feature was contributing to the issue.
I always disabled the auto start/stop before turning on the radios and driving. The BMS system varied the voltage a lot while I was driving, as low as 12.0 and up to 15.0. The inline volt meter is not capable of reading peak values, maybe there where spikes that got too high. Now that the BMS is unplugged the voltage is 13.8 at all times, just like cars used to be.
 

mmckenna

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I always disabled the auto start/stop before turning on the radios and driving. The BMS system varied the voltage a lot while I was driving, as low as 12.0 and up to 15.0. The inline volt meter is not capable of reading peak values, maybe there where spikes that got too high. Now that the BMS is unplugged the voltage is 13.8 at all times, just like cars used to be.

There certainly could be something wrong with the BMS system. Like I said, haven't seen this happen on any of the Fords at work, including a couple of hybrid police interceptors that an officer just jumps in and turns the key. And there's a ton of equipment in those cars that would complain if voltage went too high.

Might be something to have a dealership look at, or someone with a peak reading digital multimeter.
 

KB4MSZ

Billy
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Tampa, Florida
Well, February will be a year since I disconnected the BMS. If the 891 hasn't gone deaf by then I'll conclude it was a BMS power problem.
 
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