700R4 vs battery draw *Update*

[wheels87k5]

On my way to work the other day I noticed that the transmission would keep going in and out of TCC lockup. This would happen at about 60 mph while going up in speed.

I also noticed that my voltage dropped from 13 to about 10.5 v. When I come to a stop the voltage would go back to 13v. Seems that the voltage drop occurs once it gets out of 1st gear.

Huh?

 

[Fordum]

So many possibilities........
For the moment, I would ignore the dropping out of lock. I don't think the wiring going to the transmission is heavy enough to handle enough load to kill the output of a healthy alternator.
Its possible that the dropping out of lock is caused by the low voltage.

As for the low voltage, there are several possibilities. One of the most common speed related causes, is belt slippage. Pretty sure that yours is a serpentine belt. Those can slip as well.
A worn belt, or a weak tensioner will cause that.
Also an alternator can be speed sensitive.
Remember, the speed I am talking about is engine RPM.
Many alternators have to get up to a certain speed before they will start charging. However, they should keep charging once started even if the speed drops.
Also bad connections can cause voltage problems that change with load.
Try running the truck with minimum load, and watch the voltage. Then, if its normal, toss a load on it. Turn on the headlights, fan on high, things like that.
If the voltage drops, then you are on the right track.
Next, you need to measure the voltage at the back of the alternator. If the voltage drops there too, then its an alternator problem. If not, then wiring.

Check that stuff out, and get back to us. Its fixable, we just need to find the problem.

 

[Greg Ducato]

It sounds to me like the lockup drop out would be a symptom of the low voltage and not the cause, it doesn't pull enough amps for that.

 

[wheels87k5]

OK....Thanks for the information. I'll do all those checks this weekend and let you know what I found. I can use the wife's truck until then so the K5 can sit. I hate driving it with that voltage drop.

When this was happening there was no load on the truck. I didn't notice the voltage was low until heading home and I just happened to look at the volt gauge and seen it was sitting on 10.5 v. I was going 45 mph at the time. I figured that maybe the low voltage was the cause of the TCC lockup going bananas. Anyway, I was cruising at 45 mph and came to a stop light. While waiting for the light to go green I seen that the voltage was back to 13 v. I knew something wasn't right. I took off, once the light turned green, and watched the volts drop to 10.5 v. I came to a stop sign later in the trip and watched the volts jump back to 13 v right before the truck came to a complete stop. Seemed odd that the voltage comes back right before you come to a complete stop. And then shoots back to 10.5 as soon as you take off.

It would be great if was just the alternator. It's still under warranty.

 

[dyeager535]

OK....Thanks for the information. I'll do all those checks this weekend and let you know what I found. I can use the wife's truck until then so the K5 can sit. I hate driving it with that voltage drop.

When this was happening there was no load on the truck. I didn't notice the voltage was low until heading home and I just happened to look at the volt gauge and seen it was sitting on 10.5 v. I was going 45 mph at the time. I figured that maybe the low voltage was the cause of the TCC lockup going bananas. Anyway, I was cruising at 45 mph and came to a stop light. While waiting for the light to go green I seen that the voltage was back to 13 v. I knew something wasn't right. I took off, once the light turned green, and watched the volts drop to 10.5 v. I came to a stop sign later in the trip and watched the volts jump back to 13 v right before the truck came to a complete stop. Seemed odd that the voltage comes back right before you come to a complete stop. And then shoots back to 10.5 as soon as you take off.

It would be great if was just the alternator. It's still under warranty.

Just be sure to check the stupid things...connections, voltage at the battery and alternator while it's running to confirm gauge, etc.

 

[JoshHefnerX]

Sounds like a connection is loose.

 

[paratrooper307]

Sounds like a connection is loose.

That's been my problem more often than not on these trucks. I had a heater fan working intermittently. I was diagnosing the switch, relay, resistor, power connection and it was a loose ground. A couple years later the same thing happened and it was a nut on the bus bar that had worked loose.

 

[wheels87k5]

Had a little time tonight to check volt gauge connections. I did find a terminal end that wasn't crimped very good and the wire pulled right out. I fixed that but it didn't take care of the "alleged" voltage drop. I say alleged because just turning the key to on shows 10.5 volts. And the same 10.5v after starting the motor.

I'm very tired so I'm going to get some sleep but I'm wondering if it's the volt gauge going bad. The blazer will start up without any hesitation, and I have all lights and blinkers working. I have 13.0v at the alternator and the battery when it's running. I have a spare gauge so I'll check it on Saturday and let you know what I found.

Again, THANK YOU for all the input. I know some of this is common sense but I lost some of that when I said "I do".

 

[wheels87k5]

OK.....the problem with the drop in voltage is the volt gauge.

Turn key to on, volt gauge reads 10.5 volts. Remove and then test the connections to the gauge and voltmeter reads 12.2 volts. Start blazer and get 10.5 volts on gauge....connections to gauge is 14.5 volts.

As far as the 700R4, it may be a lean fuel cell causing the stumble. I'll swap out the ECM to my stock one and see if that makes a difference. And I'll do that on Saturday so more to come.

 

[wheels87k5]

Short story long.......

I had knee surgery in January. The doc trimmed off both meniscus, a bone spur and shaved off some arthritis on the back of the knee cap. The knee feels great. It will never be as good as new but it is a lot better. Next up is a knee replacement but that will hopefully be a long time from now. I was off work from Thanksgiving week, when the pain started, to the end of April. This time off included knee rehab twice a week. I was able to start working on the blazer about the end of February when it didn't hurt too much to hobble around the garage.

As an outside technician, climbing telephone poles and 28' ladders was not uncommon. I have transfers in to try and get a position that requires less climbing. So I return to work, from disability, and they offer me a data com job. One of my transfers came through at the right moment. Thankfully I came off disability when I did because the Doc was offering me 3 more weeks off if I felt it was needed. I told him the knee was feeling good and he released me on the last day the transfer was in effect. Hell yeah I accepted. No more poles or large ladders.

Anyway, I've been in training, been to a Networks Fundamentals class in Irving, Texas. And.....this job requires a lot of windshield time. I love it. So, I haven't been able to spend any time on the current issue with the blazer and the transmission.

Until..................I finally got some vacation time.

A couple of years ago I changed to an autometer speedometer and I had to buy a speed sensor to match it. This sensor mounts to the transfer case, in place of the speedometer cable, with 2 wires. One is for ground and the other for signal. I ran the wiring to the cab and made the connections. Followed instructions to calibrate the speedometer and enjoyed an awesome looking gauge panel and gauges. This lasted for about 2 minutes. For some reason the speedometer needle started bouncing. When the needle would go to the 80 mph mark it would affect the odometer reading as well. It would climb as though you were really going 80 mph when you were only going 35 mph. I thought it was the speedometer so I sent it in to autometer for repair. They said they couldn't get it to do the symptoms I described so they sent me a new one. And after I installed the new one it did the same thing. So I figured maybe the speed sensor is bad. But the ECM seemed happy. Or was it?

I did some data logging, during knee rehab time, to see how the blazer is running and could never get a decent data log. Since the speedometer would spike during the data logging it would show on the graphs and throw everything off. dyeager535 was assisting me on the data logs but I had a couple of projects come up that took precedence so the blazer was put on hold again. When I did get a little time to work on it I wanted to try get everything fixed at once. Never taking the time to figure out why I'm having so much trouble getting my blazer to run good.

Well, two days before I was to go on vacation, (4th of July week) and while heading to work, I noticed the gauges were reading a little lower than they should. Oil pressure was down 5 lbs, water temp was about 10 degrees cooler. Transmission would still stumble if you wanted to pass someone, but ran fine cruising. Nothing had changed on that. Made it to work fine.

After work I get in the K5 and it was sluggish when starting. It started but for some reason the battery was low. Took off and headed for home. Gauges were still off on the readings. I checked my blinkers and they were SUPER slow. I was starting to wonder if my alternator was dying. Made it about 10 more miles and all of a sudden the radio faded out. Crap. I turned it off and then it happened. The blazer started to die because no power to the ECM, injectors. I quickly hit the ACR switch and went to the 2nd battery. Boom, had power again. Drove the blazer home like nothing had happened. Gauges were still a little off and the transmission still stumbled under load but got it in the garage.

NOTE: I have a dual battery system with the Bluesea ACR and switch. Before the alternator went out......Whenever I started the blazer, after about 5 seconds you would hear the ACR switch on to charge the battery that was below the threshold. The sound is kind of like a dull thunk. Not loud but if anyone is standing next to the blazer, and they hear it, they look at you a little funny. During a drive you would hear the ACR switch over to another battery. When you shut off the blazer you would hear the ACR switch to off after about 15 seconds. I HAVEN'T HEARD THAT SOUND FOR ABOUT A MONTH. And didn't realize it. I haven't been driving the blazer much in the past because I was able to drive my work truck home. So there is no telling when the alternator was going bad.

Vacation time.

I had ordered a new speed sensor about 4 months back. The sensor was on back order because the person who made these sensors was on disability because of back surgery. Anyway, the new speed sensor showed up while I was on vacation so I installed it and a new alternator.

THIS FOCKING BLAZER RUNS AWESOME.

After calibration the speedometer works perfect, and the transmission doesn't stumble.

I did some data logging and there are no more spikes. I need to make some adjustments to a few fuel cells and a couple of other items and it should be done.