Need elec. help

[Dinkie Diesel]

I had my truck inspected today. It is a 2001 with 16,000 miles on it. It Flunked! Stupid High Mount Brake light doesn't work. Neither of the two bulbs light up. They wanted $12 to put in a new bulb. I almost reached across the counter and took a poke at the dude. $12????? Gimme a break! I sped off to AutoZone and bought 2 new bulbs for $3. Guess what? It isn't the bulbs. No power going to the harness at the fixture. Cargo light still works!

Can anyone out there give some ideas to check? I looked all thru the fuse block but couldn't find anything marked for the HMBL. I checked all the fuses and none were bad. What's my next step?

I went to the dealer hoping they would be kind enough to let me see a elec schematic but I might as well had my conversation with the garage door to their shop. All he could do was make an appointment for me. I just know I am going to spend hundreds of dollars to have them tell me a line of bunk. If in fact it turns out to be a harness problem will it be covered under warranty?

I can't tell for sure how long this light hasn't worked. I would like to know from you guys if there is a connection somewhere under the dash, etc. that I can check. I do have a Tekonsha brake controller hooked up. If memeory serves, I had to ScotchLock the control wire to one under the dash but that shouldn't have done it. I think it was the cold side of the switch anyway.

HELP!

[AbqGeorge]

Hmmm,

I recall sleuthing this out for a friend that had a camper topper put on. The topper place apparently didn't like the idea of that Center High Mount Stop Light coming on and lighting up the front of the topper so removed the CHMSL fuse.

Unfortunately, I let my manuals go with my 2001 6.0L "the screamer". I'm pretty sure there wasn't anything else on that line except that the lead for the CHMSL also feeds the brake controller harness and rear trailer harness.

[wangotango]

dinkie dude....relax, take a deep breath.

The signal may be CHMSL (center mount stop lamp).
It may be fuz #16, a 10 amp.

If that fuse is still good there must be another reason and it's probably not magic.

When the brake activates it illuminates the tail lights and CHMSL. Your brake lights at tail are on a ckt of there own I believe, fuz #17. Logic dictates a few things if one or the other does or doesn't work.

Fuz #14 is desiganted as STOP LPS , a 20 amp. It is related to the VEH STOP and CHMSL signals. This fuz may feed the other two.

I'll check the ckt closer if necessary.

Don't forget the ultimate reason that most auto lighting fails: inadequate,or non-existant grounds. High resistance eats up 12vdc pretty quick.

Good luck.

w/t

[IndigoDually]

Check all of your fuses with a test light. Some, like the panel lights may not show power unless turned on. IIRC the third brake light may be ground side switched. I believe that the wires run up the driver's side A-Pillar.

Good luck and keep us posted,

John

[HowieE]

Open the lamp assembly up and with a test lamp or volt meter check for voltage to a Good known ground. If you do not have voltage but do have a good fuse the wire is mostlkely open. If you have voltage there with an ohm meter check the other side to the same Good ground. If this shows open or a high resistance check the point at which that ground is connected is made or the wire leading to the ground.

If you have a public vocational school near by stop in and ask if you could get a copy of the schematic off the computer. They all have Mitchel on thier systems.

[Dinkie Diesel]

Thank You Gentlemen,
Actually, WangoTango had the best advice...take a deep breath. I am really not as dumb as my post would lead you to believe. The culprit has been identified. It was a fuse clearly marked CHMSL. In all my anger and fearing the worst I overlooked this simple matter. I checked about 14 fuses on the day of my problem and all were good. I looked in my owners manual and saw the acronym for it "CHMSL" but couldn't find in on the fuse block drawing.

All is well and thanks again!

ps Where did you guys come up with numbers for the fuses? I don't see them identified by number.

[ 02-06-2003: Message edited by: Dinkie Diesel ]</p>

[wangotango]

lucky guess

[wangotango]

upon further review:

info came directly from service manual

glad to see your problem solved

w/t