720 king cab healights/dahlights dont work

[Kingcab]

So I have a 82 720 and the healights work but they are very dimm the driver side is super dimm and when u turn on the high beem only the passenger side works and also the dash lights dont turn on and the cigarette lighter doesn't work.. what would cause all this? And is it all linked together?.. 

 

[weldingrod]

If the truck has been sitting a long time all kinds of strange and fascinating things happen to the electrical system, mostly due to corrosion. Start by cleaning/replacing your headlight plugs.

[datzenmike]

 Check the running/parking lights are they off as well? If so get them working first and this will fix the dash lights. You also need dash/running lights to power the hi/low headlight relay so that might also end up being fixed as well. The two fuses closest to the front of the truck are for the headlamps.

 

Check/clean your battery posts and cable terminals and look on the positive cable for your fusible links. (usually black and green wires) If any looks all burnt or crispy replace it.

[Charlie69]

Physically test the fuses.  I have had several of the blade fuses look good but not have continuity.

 

There are fusible links connected to the positive battery cable.

 

 

 

 

 

 

Mike any pictures of burnt fusible links?

[Kingcab]

I cleaned all connections running lights work fine. But only the dash loghts cigarette lighter dont work and the headlights are dimm and when I turn the high beems on all work besides the driver side inside light. I've checked all fuses and wires on the fusebox and the relay is branew. 

[datzenmike]

If the side marker, license, running and parking lights are working then the dash lights are disconnected somehow. Did you turn the dash light dimmer switch to full brightness???? Is the dimmer plugged in? Under the steering column are two 10 pin connectors near each other, one white and one blue (maybe green) Unplug and plug back in..... maybe the connection is poor to the dash.

 

 

Not following the headlight statement. What happens when headlamps are turned ON in the low beam position??? What happens when you switch to HI beams????

 

Do you have stock headlamps or after market????

[Kingcab]

I've changed the diner switch with a new one and I took off my cluster and cleaned all connections going to the back of it. When I turn on headlights they are dim and when I turn on high beem they are also dim but the driverside inside one doesn't work only they are also stock headlamps. I'll have to follow out every wire and see if there a broken wire somewhere as I noticed theres an old rat nest in on of the vents.

[Charlie69]

Have you cleaned grounds?

[MaxChlan]

11 hours ago, Charlie69 said:

Have you cleaned grounds?

I was just about to say that. My truck was really clean when I got it but some of the grounds had to be cleaned; definitely check those! 

[wayno]

The headlight circuit on the 720 wiring harness is a weird animal, yes you need to check your grounds, but you cannot add any grounds either.

First check to make sure the headlight plugs on the outside headlights are plugged in properly, if one is upside down it will cause issues as it puts a ground where it is not supposed to be.

Next, do you have aftermarket gauges or radio in your truck, if you do and someone wired the gauge light in it to the headlight or dash light circuits this could be your issue as this light needs to be wired in properly, neither the headlight or dash light circuits have a traditional ground, aftermarket gauge lights normally ground out to the gauge housing, this is a ground that is not supposed to be there, if one follows the wires in the stock aftermarket gauges in headlight or dash light circuits you will only find grounds before the headlight relay and at the dash light dimmer control switch, stock gauges are in plastic housings.

On the 720 diesel wiring harness the only ground wires in the plastic instrument cluster are for the seat belt and clock circuits, even the high beam indicator has no ground, it is wired into the headlight circuit without a ground because them wires are after the headlight relay, I do not know if the tach on a gas wiring harness has a ground wire.

One can wire the aftermarket gauge lights to the marker light circuit, as it does have a traditional ground, but you need to find out which wires they are behind the dash, they will be wrapped up but one does have access at the blue and white plugs and at the plug connected to the headlight switch in the column clamshell.

[Charlie69]

Great info Wayno!

[Kingcab]

Thanks for the info guys! I'll chek ibto all this when I get the chance and I'll keep you all posted on what I find out 

[Kingcab]

Another question unrelated.. but I was wondering if the timing chain xover from the z22 would bolt on to the l20b..

[datzenmike]

Timing cover? Yes, perfectly, but the top part under the head isn't a perfect match. The shape and the bolt holes don't match, but as this only seals in oil spray and fumes you could probably seal it up without them. .

[Kingcab]

How would I go about sealing it up? Would it be easy and affective?or lots of modding and brazing?  As my front cover for my l20b is worped and leaks lots of oil. 

[Charlie69]

Buy another used front cover.  Cheaper than buying oil all the time.

[Kingcab]

I cannot find one neer me that's guaranteed not worped for a decent price. And I have 2 z22 motors laying around and thought maybe I could use It free of charge other than some cilicone gasket maybe 

[datzenmike]

 

Place a Z22 head gasket onto the bottom of your L head. The gasket is different but covers and seals everywhere but is thinnest in this corner, near the fuel pump above. I blobbed some JB Weld in this corner and filed it down by hand to make it wider here. The head and the timing cover just barely pinches the gasket in this area. When assembling you could rub a thin smear of RTV on the outward facing contact on the sides and front of the timing chain surfaces.

 

None of the 10mm bolts in the timing chain area will line up, but as I said it just has to seal in fumes and oil spray

[Kingcab]

Thays really good info to have! Thanks! ... i think my l20b front cover is worped is why I'm asking about this. Would it be easier/more affective to just resurface the l20b front cover? 

[Kingcab]

I resurfaced the head with a flat board and sand paper I was wondering if it would be more worth it to do the same to the front cover.. as it has the studs in it and not sure if there removable for the process...

[Kingcab]

Sorry to be all over the place but the headlight issue was a loos terminal. But the dash light and cig lighter still dont workk

[datzenmike]

2 hours ago, Kingcab said:

I resurfaced the head with a flat board and sand paper I was wondering if it would be more worth it to do the same to the front cover.. as it has the studs in it and not sure if there removable for the process...

 

Thy can be pulled out with vice-grips. They are critical for proper alignment of the front cover so are needed. Why would you think it's warped?

[Kingcab]

Its leaks oil badly from the front cover and I have replaced the gasket multiple times.

[datzenmike]

Did you also replace the front crank seal? These are the usual cause of drips. Also a very small dab of RTV where the oil pan, timing cover and the block meet on each side. Then the timing cover, block and head where they meet on both sides at the top.

[Kingcab]

I rebuilt the bottom end about 4000 miles ago..

 I bored out 1mm bigger than factory..

  I put bran new pistons crank bearings front and rear main seals, oil pan seal front cover seal and head gasket also all coolant and oil pump gasket. As we all as tranmiston seals.