strange voltage prob?

[WyoSyclone]

Re: strange voltage prob?

Try an experiment real quick.
The fog lights are supposed to go off when the high beams are on. The left front high beam supplies voltage to the 'fog lamp relay', energizing the coil, breaking the relay circuit, and shutting the fog lamps off. Turn your lights on, flip on your high beams and see if the fog lamps go off.

That fog light relay is just above and to the right of the access panel to the fuse box. If the fogs don't go off when the high beams are on, the relay is shot. I'd also inspect the wiring around that relay for damage from your 'fire'.

If a relay is carrying a lot of load through the coil (damaged or worn out coil), when the coil de-energizes it can cause a back emf voltage of up to 200 volts (big relays)... it's possible that the 17 volts you're seeing could be caused by back emf from the relay.

If it was me I'd just replace the relay for peace of mind.... Also, the circuit breaker at the fuse box should be tripping if there is that much current being pulled. If it's not tripping I'd probably replace it as well just to be safe.

 

[BoostedSUV]

Re: strange voltage prob?

Wyo I will give that a shot when I get home from work. I know the foglights turn off when the high beams are on though.

I am also going to make sure for certain that I have the correct fog light bulbs in place. I will mess with it tonight.

 

[WyoSyclone]

Re: strange voltage prob?

Wyo I will give that a shot when I get home from work. I know the foglights turn off when the high beams are on though.

I am also going to make sure for certain that I have the correct fog light bulbs in place. I will mess with it tonight.

You could always put an ampmeter in line, in the feed going to the foglights and see what kind of current you're pulling.

 

[BoostedSUV]

Re: strange voltage prob?

I just went out and verified, the fogs do turn off when the high beams are switched on. I believe I have another relay off the 'fire' harness I removed but since this existed prior that may not be the issue. I used to melt fuses if I left the fogs on for too long. Took an electrical fire and trial and error to determine this. I just need to track this down, I want everything working properly.

 

[WyoSyclone]

Re: strange voltage prob?

I just went out and verified, the fogs do turn off when the high beams are switched on. I believe I have another relay off the 'fire' harness I removed but since this existed prior that may not be the issue. I used to melt fuses if I left the fogs on for too long. Took an electrical fire and trial and error to determine this. I just need to track this down, I want everything working properly.

Which fuses were you melting? Did you replace the fuseblock/box?

 

[BoostedSUV]

Re: strange voltage prob?

If I remember correctly it was the third fuse up from the bottom on the left side of fuse box. Fuse box and entire interior harness was replaced after I melted the fuse box.

 

[WyoSyclone]

Re: strange voltage prob?

If I remember correctly it was the third fuse up from the bottom on the left side of fuse box. Fuse box and entire interior harness was replaced after I melted the fuse box.

That would make sense.. that's on the same bus bar as the fogs.... in checking the grounds did you check the one beside/behind the factory air cleaner housing - beside the horn bracket.... this is the ground for the fogs.
Also, the main bus bar ground (look like a bent metal plate with six fingers beneath the dash on driver's side)... make sure it's solidly grounded to it's mounting location... black wire coming off of it going up to an 8-pin connector - make sure that black wire is grounded well.

 

[kentuc]

Re: strange voltage prob?

Disconnect one fog at a time and see if anything changes.

 

[BoostedSUV]

Re: strange voltage prob?

I've checked the ground bar under the dash a few times and its secure. The only ground I found on the driver side was by the upper radiator hose on the rad support.
I relocated my battery to where the air box used to be so if its behind there I'm betting I need to look there! My horn has been sounding like its dying for a while now so if the fogs and the horn share a ground that's a great place to look! I never related the 2 to each other and I forgot about the horn because I haven't used it. You may have just centralized my problem. I will check tonight and see if I can find where that ground is.

 

[BoostedSUV]

Re: strange voltage prob?

Or should I say you just found the "common ground" between the 2! Lol

 

[WyoSyclone]

Re: strange voltage prob?

My horn has been sounding like its dying for a while now so if the fogs and the horn share a ground that's a great place to look!

Yup, they share the same grounding point.... single wire for the horn, two wires into single ring terminal for the fogs. They just go into the sheet metal with a self tapping screw... I replaced mine with a bolt and starwashers. Good luck!

 

[WyoSyclone]

Re: strange voltage prob?

:rotf:

Or should I say you just found the "common ground" between the 2! Lol

 

[BoostedSUV]

Re: strange voltage prob?

Well I pulled out the relocated battery and checked the grounds for the horn/fog lights. Everything was tight and intact, but I cleaned them up anyway and tightened them up. Horn wasn't working because the battery was against it and caused a bad ground on the self grounding horn bracket. I relocated the horn and made a bracket off a charcoal canister bolt. Horn works great now, but I'm still having the voltage issue with the fog lights. I'm going to have to put the multimeter on the fuse and see how much of a voltage drop I'm talking about because it doesn't show up at the battery. I know a drop in voltage in is normal but my case seems extreme.

I am going to verify that the correct bulbs are in place and try unplugging one light at a time and see if I can isolate the problem. This is getting frustrating. I ran out of time tonight but I will try a few other things mentioned when i get a few minutes. Thanks for all the continuing help! At least I got my horn working in the process :tup:

 

[BoostedSUV]

Re: strange voltage prob?

They share the same FUSE, too. "HRN/DME"

The fogs get their B+ from the hrn/dme fuse. This power comes through the bulkhead connector. You could have a resistive connection at the engine harness-to-bulkhead connector.

Dve is there any good way to determine this? I've got the horn working now but still having the same issue wih fogs. Could this explain my originsl issue why the voltage doesn't move at the battery but the gauge will read lower sometimes and if I turn fogs on and off it will read normal again?

I don't know if I mentioned it in this thread but I swapped out my 92 fuse panel/dash harness with one from a 93. I had other issues with this swap that I straightened out (ie wires in different positions etc), did I miss another one?

 

[BoostedSUV]

Re: strange voltage prob?

I just read the origional post again. Do I have this right? Truck starts, and voltages appear normal. After a period of time, the voltage (as indicated on the dash) falls, and it runs crappy (or 'different'). Cycling the fogs brings the voltage back to 'normal'.

If I have it right, does cycling another heavy-draw like the headlights or defogger, or high-blower motor accomplish the same results?

This looks like an alternator, or alternator wiring problem. Be sure you have system voltage at the pnk/blk wire at the alternator plug. Pull back the taping and covering for a few inches and inspect this wire. You would not be the first to find previous "repairs" in this area.

I don't think the problem you're trying to 'fix' has anything to do with the fogs themselves. It just is affected by the current-draw of the fogs. You need to keep looking. Sorry. I know this is not the 'help' you were hoping for.

That pretty much sums it up... To answer your question only the cycling the fog lights bring the voltage reading back to normal. Nothing else "hits" hard enough to spike it back to normal. I will check the wires at the back of the alternator again but I didnt notice any problems there when I went over everything when the engine was out. The fog lights still seem to spike the voltage wayyy more than normal. The needle hardly moves with everything in the truck turned on but it will jump down and stay there with just the fogs/parking lights on.

 

[BoostedSUV]

Re: strange voltage prob?

here's a visual that for you you guys that I took with my camera phone on way home from work. The Angle of the camera makes it appear lower than it actually is. It's about a needle width higher then midway mark in fist pic from my viewing angle.

First pic, lights on, radio on (2 amps, 2 subs), wipers on, elec fan on, foot on brake.

Second pic, same as above but turned fog lights on... Significant drop in voltage!

 

[BoostedSUV]

Re: strange voltage prob?

Dave as soon as I get day here in NJ when it's not raining (been a while) I will take the multimeter out side and report back on those finds. Thanks for taking the time to break that down for me where and what to check for.

 

[BoostedSUV]

Re: strange voltage prob?

ok I lied I sucked it up and went out in the rain. Here's my finding hope they make sense.

this is how I'm going to break it down <fogs on / fogs off>:

neg lead of meter on Alt housing:
neg batt post <.05 / .03>
engine block <.03 / .03>
Ground off intake bolt <.03 / .03>
Firewall ground strap <.10 / .09>
Cig lighter shell <.10 / .09>
Buss Bar <.10 / .09>

Pos lead on Alt post:
bat pos term <.05 / .05>
Firewall junction <.15 / .23>
pink coil wire <.40 / .40>

Checked all the fuses and they appeared to be within .1 except Horn fuse (makes sense)
fogs off <.60 / .45>
Fogs on <.83 / .58>

I'm not sure what this really indicates but the horn/fogs fuse is warm to the touch, and hot with fogs on. This is the circuit that melted and caught fire on the old harness so my issue definitely lies there somewhere!

 

[BoostedSUV]

Re: strange voltage prob?

Alright to answer the questions.. Alternator is an Autozone reman, higher amp than stock maybe 140? Crank pulley is stock and the Alt pulley is the one that came with the Alt -2 3/8" to the outer edge. I pulled the fog bulbs out and changed them with a verified set of 55watters and no change. I had the truck idle while I testing everything and with the elec fan/head/park/hood/interior lights on the volt Gauge hardly moved. As soon as the I flipped on the fog lights the truck would barely idle and actually shut off a few times. It starts idling rough and sounds like it gets a slight miss with the fog lights on. The volt gauge doesn't continue to drop after turning them on it just falls hard and stays there. The Pics are about where it stays once warmed up. Alt puts out 13.9 cold and 13.6 hot. Voltage to the battery does not move no matter if the fogs or on or off. Only seems to affect the volt gauge in the dash and the way that the truck is running. When I say it barely idles with the fogs on it's no exaggeration!

I would probably agree that the Alt is the problem but I can turn every single thing I have on in the truck and hardly budge the Volt gauge (head lights, high beams, stereo blasting, front and rear wipers, blower motor, interior lights, rear defrost, elec fan etc) It's when the fogs and only the fogs, even if I have everything off except parking lights and fog lights does the volt gauge show any idication of low voltage.

 

[BoostedSUV]

Re: strange voltage prob?

I will definitely give that a shot this weekend. That's pretty much what I did with my fuel pump, it was heating up the ECMB fuse so I ran a 10ga wire from the Alt stud back to a relay and T-ed into the factory fuel pump harness and solved that problem and it actually feeds the pump more volts. Same thing I did with the power feed to the ECM because it was dropping to 12.1 at WOT, now it stays steady at 13.8. Same concept I'm guessing.

Can I go to firewall junction block which is fed by the Alt or Is the Alt post better? Just asking because I think that would look cleaner and I already have 3 or 4 wires off the alt stud, is there a limit? haha