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Topic: Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ? (Read 2943 times) previous topic - next topic

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Hello there, I THINK I’ve got an electrical problem starting to develop. First of all, where’s what I have. It’s an ’86 Turbo Coupe. Everything is stock, except for the 3G swap, and an aftermarket stereo (no amps or anything, just the stereo). The 3g swap is probably about six months old, and the stereo has been in there for about three years. I haven’t had an issue with anything until now.

It started about nine months ago. When I would start my car, the idle would pick up for about ten seconds, and then drop down to a raggedy idle for two or three, then go back to normal. I probably should have investigated it then, but I just worked around it—figured it might have been a charging issue and the 3G would remedy it…nope. So for the past couple days, while driving, I’ve been noticing some oddities. The speedo needle would jump while at stoplights, I’d put my foot on the brake, and the radio would shut off and come back on, and most noticeably today, the power would cut in and out while driving. Not completely, it would feel like going from half-throttle to part-throttle. I’m kinda stumped here. I haven’t been under the hood or dash fiddling with anything; this just started and is progressively getting worse. I don’t think it’s the alternator, but I can’t be for sure. The car starts up fine, doesn’t seem to be affected when the lights come on, or any other electrical device, but it still seems to be electrical in some way. Any idea where I should start? Any of these symptoms sound familiar? Need any more info? As long as the car holds up until Saturday, it’ll be a weekend project. Thanks!

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #1 –
Geez, no takers? Oh well, I know when it comes to electrical gremlins, I'm hatin' life--kinda like now...lol...New info: I leave for home last night, I start the car and get under the hood and jiggle every wire I could see. Nothing. The drive home was perfect...everywhere I drove, absolutely perfect. This morning--back to the glitches! So, these past two mornings have been cold and damp, so I'm starting to lean towards a short somewhere...possibly a bad ground? I know the battery cables look like they're the original ones, so I think I will replace them to see if the improved ground makes a difference. If that doesn't help, I'm thinking about having the diodes in the alternator checked. What about the ECM?

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #2 –
Have the alternator checked. Auto Zone, etc. will test for free, sometimes on the vehicle without having to remove it.
I believe '86 TC's also had an external voltage regulator. That may be going bad.
And to be thorough, you may want to install a new ignition switch.

The symptoms you describe sound a lot like a bad alternator and/or regulator though.

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #3 –
Has the ignition switch ever been replaced?
I don't mean where the key goes, I'm talking about the piece under the trim in the column...Ford has had a lot of recalls in the last 15-20 years over those, and when they start going bad, all kinds of crazy issues develop. Just a thought. If it still does it after that is resolved, I'd look into your grounds for the cluster/dash area. Either get or ask Jcassity or ThunderChicken for advice..they are electrical gurus here.

Good luck!
'98 Explorer 5.0
'20 Malibu (I know, Chevy, but, 35MPG. Let's go brandon, eh)

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #4 –
Thanks for the reply guys!
I upgraded to a 3G alternator a few months ago, but it's a junkyard alt...I had purchased one before, tested it, and it was fine and then when I went to put it on, found that it was too big to fit in the bracket! Made a mad rush to a nearby salvage yard to yank another one, slapped it on and crossed my fingers. So, it may very well be on its way out.
Yes, I replaced the switch in the column the first week I had it. I've done it twice before on my Mustang. I'd say that switch is right at three years old.
I think I'll get the alternator tested, and if it's still having issues, start checking grounds in the dash area. I'll keep Jcassity and ThunderChicken in mind. Thanks again guys. Much appreciated.

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #5 –
Okay...it's only stumbled once since I posted. We've been having a run of warm weather, so it's been good. I'm still gonna get the alternator checked out though. Hey, when i unplug the alternator to see if the problem persists with it out of the loop, am I supposed to jump any of the terminals? I tried to see how it would do the other day and the car just died.

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #6 –
Sounds like a typical ignition switch issue or the connector. The alternator should be fine because even if it was intermittent the battery would be charged enough to carry the load of the vehicle. Sounds like a bad connection. Try and see if the things that are effected are common to key battery or non key battery. This way you can isolate the problem. My money is the Ignition Switch or Connector. Their is only one way to eliminate ignition switch issues in those cars. That is to slave out the ACC side of the switch supply with a relay. As we speak i am doing a MUSTANG head light switch modification and will post some photos of slave relay control.
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #7 –
Hmm...the Ignition Swith is the first thing I replaced when I bought the car. Do you think maybe it's because I bought a cheap, aftermarket switch and it's going out already? Are you talking about the connector that plugs into the Ignition Switch?

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #8 –
Yes even a relatively new switch can cause issues, But if its new i would not suspect it but i have seen them go south in as little as 6 months. This depends on the usage of accessories. Mostly the ac and blower circuits put a heavy load on the switch.
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #9 –
Interesting you should say that. I use my AC a lot. So, you're suggesting to put a relay where? Sounds like you mean to route all the power through the relay and just use the ignition switch as the trigger. Am I close?

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #10 –
Quote from: BlackCardinal;363302
Interesting you should say that. I use my AC a lot. So, you're suggesting to put a relay where? Sounds like you mean to route all the power through the relay and just use the ignition switch as the trigger. Am I close?

You GOT IT i just did a mustang fog head light mod.

http://i600.photobucket.com/albums/tt88/tomrenzo/001-6.jpg Burnt switch and plug

http://i600.photobucket.com/albums/tt88/tomrenzo/002-3.jpg First wire in the relays

http://i600.photobucket.com/albums/tt88/tomrenzo/003-2.jpg Then make them NEAT

http://i600.photobucket.com/albums/tt88/tomrenzo/004-1.jpg Then push the relays behind the dash PRESTO NEAT AS A PIN Thanks
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!
 

Speedo needle jumping, radio cuts out with brake pedal, Charging system issues, or ?

Reply #11 –
Thanks!