New M1008 with Headlight issues

[ChrisG]

Picked up an 85 cucv I have owned a bunch of these 80s GM trucks and have always wanted one of these but could never get to them quick enough when they came up for sale. Truck had not been started for three yrs and had pass.side alternator issue which turned out to be missing insulators inside. Replaced those put in new batteries and it cranked right up and runs like a top.
The headlights do not come on taillights parking and directionals all work. I have not bought new headlights yet but did probe around plugin and there does not seem to be any power to back of headlightI have read through most off the stickies about headlights. What position should the black out controls be in exactly, left control only seems to stay in middle position. Will the harness upgrade only fix this?
I am jumping the gun on questions a little as i really haven't had time to thoroughly troubleshoot this problem. The horn also stays on hoping that clipping out diode will cure that bypassed suppressor already,maybe needs new relay too?
Thanks for any help and love the site.

 

[Warthog]

Welcome to the site.

The horn on issue can have an effect on the headlights.

Do some troubleshooting and report back. Could be as easy as bad headlight bulbs.

 

[dependable]

Nice truck. Looks just like one of mine that is painted dark green, except my grill and bumper green too.

Sounds like you know about the horn diode. Cutting it will probably be all you need to do if it is stuck on.

Black out switch returns to middle. Just don't leave on, good way to drain your batteries. Other switch normally should be in up position.

 

[Evil Dr. Porkchop]

Welcome from VT. Nice truck!

 

[Al Harvey]

Welcome from Tennessee.

 

[ChrisG]

Dr Porkchop think I talked to you about bumpers and clevis's maybe.
Went home at lunch and cutout horn diode,cured horn issue and rest of driving lights work have reverse lights too, very bright now actually. Still no power to headlights though...

 

[cucvrus]

Headlamp dimmer switch can be the issue with no headlamps. That is fairly easy and inexpensive to fix.

 

[ChrisG]

So does the headlight harness upgrade continue back to headlight switch and that is what controls on/off? read the stickies just didnt see where it says how it gets switched power.

 

[Assel]

welcome from south germany

 

[Warthog]

So does the headlight harness upgrade continue back to headlight switch and that is what controls on/off? read the stickies just didnt see where it says how it gets switched power.

The stock headlight wiring supplies power to the headlight upgrade harness. It supplies 12v to the new relays that feed the headlights.

You switch on the stock headlight controls and instead of supplying a bunch of power to the bulbs, it supplies a little power to the relays.

Before you think about adding the new harness you need to make sure your stock wiring is working properly.

Do you have a multimeter and know how to use it? You need to see if you are getting voltage to the plugs at the headlights.

 

[ChrisG]

Yes I do and will...I know im jumping the gun a little just trying to get heads up on how that upgrade works. Just quickly poking around with test light it doesnt appear there is power at plugs. I need to do complete troubleshoot procedure. And i do know a test light is not a multimeter... lol.
Thanks again for quick responses. This weekend will be when I can really spend some time on it. Any quick thoughts as to why there is no power to headlights and all other lights work...fuse is good i do know that wires look to be intact...I know I know continuity test...

 

[victor3ranger]

Welcome to the site, I just got my first 1984 M1008, you are lucky mine is a real pain to get started.

 

[ChrisG]

Yes I think I did quite well with this truck. It was a maintenance vehicle for a retirement home for a number of yrs and appears it was really well taken care off. Knock on wood every issue so far has been very easy to resolve.
Not as easy as the last 87 1 ton I bought that guy swore it needed fuel pumps and on and on....it was out of gas...

 

[Warthog]

Straight from the troubleshooting section of the TM 9-2320-289-20 tech manual:

33. HEADLIGHTS INOPERATIVE IN HIGH AND LOW BEAM (ALL OTHER LIGHTS OPERATE)
NOTE
It may be necessary to remove headlights to perform this step.

Step 1. Check for voltage at headlight connectors.
If there is voltage, replace headlights. (See paragraph 4-24)
If there is no voltage, trace circuit from headlight connectors to blackout
toggle switch. (See wiring diagram F-13 or F-16)

Have you figured out the Black out light switch positions? It is covered in the TM 9-2320-289-10 Operators manual.

Some areas to look at:
B/O Service Switch
Headlight switch
wiring
the firewall wiring connection plug

harder items to check:

dimmer switch
dimmer switch linkage

 

[Recovry4x4]

Welcome from Sunny and "Too dam Hot" So. Florida.

 

[ChrisG]

Okay so I had some time last night to work on getting the lights working. Everything except the headlights works now, appears blackout switchs work, maybe not sure. There is no power to headlights started pulling dash apart got BO switch plate out but ran out of time to mess with it. The truck came with a fairly large parts break down and service troubleshoot manual (pic) but there is barely a reference to the headlights in it. Tried searching stickies on here without much success,my laptop was not cooperating.
So in this scenario what would be the most common cause for this headlight issue happening?
I have been involved in other forums and I get the deal about a new guy posting a question that has been asked and answered a hundred times so I apologize if this is the case,which I know it is.
Thanks

 

[Warthog]

You need the TM 9-2320-289-20 manual. It covers more of the basic/electrical troubleshooting. Your TM 9-2320-289-34 is more for the major components. We have all the manuals for free here.

Your headlight problem is a specific issue and it is "okay" to ask about it. The problem comes when someone asks "how much oil" or "What is this dohicky".

We will be glad to help you fix the light issue.

I have written a lot of the CUCV stickies and know the CUCV electrical system very well. Here is a link to the Headlight sticky which traces the headlight circuit from one end to the other.

http://www.steelsoldiers.com/showthread.php?87544-CUCV-Headlight-Circuit

 

[Warthog]

I changed the thread title so others with headlight issues can find it.

From your description so far it sounds like you have power through the Blackout switch and the headlight switch.

Next I would disconnect the plug from the dimmer switch and see if you have power there. The switch is described in the TM 9-2320-289-34 manual you have on hand. Section 4-13, page 4-92.

5th picture in this thread

http://www.steelsoldiers.com/showthread.php?50551-CUCV-Switches-Diodes-Relays

Remove it and check for voltage on the yellow wire ( This is with the BO Service switch in the up position and the headlight switch pulled out)



If you have 12v with the switches on, use a jumper wire from the yellow wire to the light green (high beam) and tan (low beam) and see if the headlights are working. If they do then the dimmer switch is the problem. If not then you will need to proceed to the engine compartment and start checking the headlight harness.

 

[ChrisG]

Thanks for your patience...just read thru that whole stickie again. Think i will try the service switch bypass I read about on here just to eliminate that from the equation for now. I did notice the headlight fuse is very loose. Whats puzzling is that when I read through other posts there seems to be a combination of issues associated with headlights not working and every other electrical item works except the headlights on this truck. Im going to check couple things at lunch...

 

[ChrisG]

Thanks Warthog all good info. Gonna try and do that at lunch.