Dim lights when I clutch??

[66Sprinter]

I have a new problem with electrical dimming when I push in the clutch.

With the engine off and selectively turning on power items like parking lites, head lites, radio, fan. etc...the volts go lower on the battery..but there is no change when I push in the clutch. So on that note I figure that I am not having any wiring problems. :roll:

T5 not in gear and Engine running at startup and with a meter on the battery..I am running 14.8volts..when I push in the clutch it goes to 14.3 volts...when the choke finally settles the RPM's I am running about 800rpms and the meter reads 14.5 volts..when I push in the clutch it goes down to 14.0.


I am using the stock 65 amp alternator...but with the battery at 14.5 volts : I am not sure where to look next. Its only a 0.5amp loss but when driving at night the lights do dim and sometimes my MP3 player will quit.

Any suggestions or ideas???

 

[MustangSix]

When you push in the clutch, the engine is getting more load because of the extra friction of the release bearing and thrust bearing. That may be enough to cause the engine to drop 50-75 rpm.

At idle the stock alternator is not putting out much current. It should read in the 14-14.7 V range. But because it is putting out so little juice, the voltage will drop with even a small dip in rpm.

 

[66Sprinter]

Jack if I read you right..then a simple change to a 100amp alternator is all that I need?

 

[Mustangaroo]

Why? Why install a larger amp? It will just require more HP to turn, less to the wheels! If you havn't installed anything needing more amps than a stock setup why change?

 

[66Sprinter]

Well...I guess the first issue is that I dont want my lights dimming while driving at night....and the MP3 player thing..

However, I guess my choices would be to either rewire the lights directly from the alternator...(wouldn't that be a no change in the dimming) or add a larger amp alt to keep me up at power...if there are other choices then...I am open to listen...although I am going to retune the car today to make sure that we are in optimum condition

I also remember a post about alternators sometime ago..so I may do a search and see whats up with that

Jim

 

[MustangSix]

This should only be a problem at idle if everything is working correctly. And it shouldn't be a dramatic difference. If it dims the lights significantly, you may need to check the alternator. It's possible to blow a single diode and still have the alternator putting out current.

If you're running a lot of other things (amps, fans, fog lights, EFI, MSD) then you may need a bigger alternator as well. The best upgrade IMO would be a 3G 130amp alternator. I have one on the Locost and will install one on the Mustang eventually.

 

[66Sprinter]

Jack...

My problem occurs at both idle and while driving and shifting. I originally thought I was bumping a wire under the dash...but last night the lights go dim while I am at the stop light...

???? :roll:

 

[addo]

Headlight switch?

 

[MustangSix]

I'm with Addo. Check under the dash to see if you're hitting anything with the clutch or linkage. Most of your underdaash wiring is in that vicinity.

 

[66Sprinter]

I am pretty sure thats not it. I tested the circuit...engine off...and with the lights on and pushing in the clutch...no dim

While my wiring isnt all new....it is good.

This only happens with the engine running...

I am tempted to

(1) wire the headlights via relays
(2) replace charging sensor
(3) upgrade to higher amp alternator via MAD

Any other thoughts...It really kills me not to run around at night due to embarass ment....and I just put in a new windshield so I can see at night :x

 

[addo]

Well, your lights will appreciate the "straight shot", no matter what creates the energy. I have a harness with a funky old period-correct relay (New Era brand) - it's about the size of the early Autolite generator regulators. Or you could gut a spare reg, and hide a couple of new Bosch relays under it.

Work with what you've got for starters, rather than adding further unknowns. If the lights are no better, then consider an appropriate upgrade.

Cheers, Adam.

 

[Lazy JW]

If the voltage doesn't drop below 14.3 volts as Jammer noted, then the stock unit is obviously keeping up and a bigger alternator won't help. I suspect something under the dash also. Make absolutely certain that the dash is securely grounded to everything else. All connections need to be clean and tight.
Joe

 

[66Sprinter]

Guys....I really appreciate the help. I am heading out in a few hours (VACATION DAY FOR ME! ) to look up the relays and stuff and will try that route first. I think my alt is fine..it is only a year old and I have no other supply problems. Also new plugs and a tune since I just put a new 1100 on.

Remember back in my orig post. I tested the clutch with no engine running and all things on and got no dimming or change in voltage at the battery when the clutch was depressed....so again..I am ruling out the wiring issues under the dash. (That is where I first spent about 45 mins doing the checking anyways)

The note Jack brings up about the friction and loss of RPM makes sense for me.

Is there a smaller pulley for the stock alt? Would that help? Maybe a new regulator?

 

[Anonymous]

I changed to a GM style (I know I know, tho it is cheaper and easier) Powermaster 100amp alt... and my car runs alot better! But my voltage was dropping down below 13 when it was idling in gear (automatic). Now it never drops below 14.5v no matter what I have on. I am running a MSD 6, so I know when you give them better voltage, it'll work better..

Why? Why install a larger amp? It will just require more HP to turn, less to the wheels!

I don't think a larger alt is going to create more drag unless it is under more load. I would think a 100a alt putting out 30a would making less of a load on the motor than a 60a alt putting out 30a (much less a 40a which is what most of our Fords came stock with)