Thread: 302 Stroker??

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Originally Posted by 34_40

Got the linkage "more secure" and took it out early Sunday morning before it got hot out. I think I want to adjust the Throttle Valve just a touch more to hold the shift points just a bit longer.

At one point on the ride I jumped on the highway and ran it up to 70 / 75 and suddenly my gauges go flukey.. Tach swinging all over the place, speedo the same - it was weird!! So I've been thinking about and I'm thinking it was the cooling fans freewheeling and acting like generators. I know others have had this happen but don't remember what they did to negate the effect. I've been mulling over installing diodes to stop the backfeed..

So anyone remember this saga and what was done ??? TIA

Well, Mike, we all know I'm not a wiring guru (surprise!) so I have no idea why your gauges went all flukey but freewheeling fans acting like generators probably would have never come to my mind. Just curious how the fans are controlled? Was your "flukiness" confined to the gauges or did it also affect how the car was running at the time?

I'm thinking an intermittent ground problem, a battery going to ground or an alternator getting crazy. I can't buy the motors acting like generators.

I guess nothing is impossible.. intermittant ground? I don't know, as the ignition didn't skip a beat.
And I have heard of this before, just don't remember where I read it. So I thought I'd ask here if someone remembered the topic.

Are you thinking of a flyback diode - Flyback diode - Wikipedia, the free encyclopedia From what I see the diode is there to protect the contacts in the relay from arcing, not from pushing power into the system vs being driven. I'm a gearhead vs a spark chaser, and that generator thing just doesn't make sense to me. Then again, on big power generators (electric utility size) one of the most important pieces in the generation controls is the backfeed prevention to keep from motoring the generator with grid power if the turbine trips..... I think you've got some other gremlin to chase, and good luck with it!! Keep us in the loop as you try/find things. Interesting, interesting......

Disconnect components until it goes away.

Just run for short periods with the components isolated.

I'd start with the alternator.

A capacitor to ground might be the ticket for your fans, maybe an in-line diode as well.

Originally Posted by rspears

Are you thinking of a flyback diode - Flyback diode - Wikipedia, the free encyclopedia From what I see the diode is there to protect the contacts in the relay from arcing, not from pushing power into the system vs being driven. I'm a gearhead vs a spark chaser, and that generator thing just doesn't make sense to me. Then again, on big power generators (electric utility size) one of the most important pieces in the generation controls is the backfeed prevention to keep from motoring the generator with grid power if the turbine trips..... I think you've got some other gremlin to chase, and good luck with it!! Keep us in the loop as you try/find things. Interesting, interesting......

Yes, the diode acts as a one way valve to stop the backfeed. I also realized that I had changed the wires when I re-installed everything. Before the dual fans were wired in series. I became concerned that a single failure would take out both fans so I changed the connections so each fan is independent but share a common power supply. (As an aside, when running dual emergency generator sets, a synchronizor on the motor govenors must be used as one generator will become dominant and force the other generator to become a motor and drive the prime mover.. so you end up with a electric motor driving the engine! The synchro keeps the generator output matched and in phase.)

Originally Posted by firebird77clone

Disconnect components until it goes away.
Just run for short periods with the components isolated.
I'd start with the alternator.
A capacitor to ground might be the ticket for your fans, maybe an in-line diode as well.

I think a diode would be the way to go if I can prove the fans can become a generator. I know it is potentially possible depending on the motor. I just don't know these fan motors. Since it only happens above 70, I don't see me "testing" many things on the highway. But thanks for the thought~~

Originally Posted by randyr

Well, Mike, we all know I'm not a wiring guru (surprise!) so I have no idea why your gauges went all flukey but freewheeling fans acting like generators probably would have never come to my mind. Just curious how the fans are controlled? Was your "flukiness" confined to the gauges or did it also affect how the car was running at the time?

Seems I also missed some of your questions. I have a relay which is controlled by a "sending unit" in the intake. At 180 degrees the S.U. closes to establish a ground circuit and the relay latches closed. At 165 degrees the S.U. opens and the relay also opens. I can't swear what all the other gauges were doing, but, I know the tach and speedo were going nuts! Once I got back to 65 and below.. the gauges returned to normal.. HTH..

Had similar issues once upon a time with an electric speedometer.....is yours electric or mechanical???

The one I had trouble with was a Dakota Digital....took the dash unit and speedo to them, they did some of their wizardry, no more problem.

And that would be pretty much be the extent of my knowledge on feedback problems!!!!!!!!!

Originally Posted by Dave Severson

Had similar issues once upon a time with an electric speedometer.....is yours electric or mechanical???
The one I had trouble with was a Dakota Digital....took the dash unit and speedo to them, they did some of their wizardry, no more problem.
And that would be pretty much be the extent of my knowledge on feedback problems!!!!!!!!!

Yeah, it's electric.. The other change that was made over the winter was the lower pan behind the grille was added. To help force all the air through the radiator..
Is this the culprit?? I don't know.. I guess I'll just drive it the speed limit and it'll be fixed!

HAH! NOT!!!

I think I have another fan from a wrecked vehicle. I'm wondering how my buddy will feel about holding it out the window while we run down the highway with it hung out there with a volt meter attached?!?!?! rofl..

Originally Posted by 34_40

...I think I have another fan from a wrecked vehicle. I'm wondering how my buddy will feel about holding it out the window while we run down the highway with it hung out there with a volt meter attached?!?!?! rofl..

Let's see, you're sayin' I can buy a Prius or Volt, mount a bunch of electric fans anywhere they will catch air going down the road and I'll have a perpetual motion machine that runs off the batteries, but re-charges the batteries from the air velocity through the fans?? Too many things wrong with that picture, Mike.

Originally Posted by rspears

Let's see, you're sayin' I can buy a Prius or Volt, mount a bunch of electric fans anywhere they will catch air going down the road and I'll have a perpetual motion machine that runs off the batteries, but re-charges the batteries from the air velocity through the fans?? Too many things wrong with that picture, Mike.

You're funny! No, that's not what I'm saying! But what I am investigating is a fan motor(s) becoming a generator that's out of phase with the rest of my electric system. Something is causing the speedo and tach to go crazy! Didin't check the other gauges so I can't speak about them.. And don't you know sarcasm when you read it??? And here I thought I was transparent!

If your speedo and tack are digital it could be a frequency feedback from the fans that is causing the problem, a ferrite bead could possibly be the solution.

Only above 70, I missed that part.


Sounds like an AC component in your power.

Fans sound like a good suspect.

Originally Posted by 36 sedan

If your speedo and tack are digital it could be a frequency feedback from the fans that is causing the problem, a ferrite bead could possibly be the solution.

No, they aren't digital but they are electronic.. Tell me more about this ferrite bead?

Originally Posted by firebird77clone

Only above 70, I missed that part.
Sounds like an AC component in your power.

Fans sound like a good suspect.

That's what I was thinking! I may be way off base but I have heard of it before!

Sounds to me like the flux capacitor is whacko again, hate it when that happens!!!!!!!