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electrical gremlin. any ideas?

J.Peart

J.Peart

Active Member
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Location
Kelowna, bc, canada
Started up my truck after work and had some odd problems. all seem they could be related to dash electronics.

the airbag light is on.
the front blower wont turn on.
the wipers wont turn on.
front diff wont engage.
the gear indicator light isnt on.
abs light is off (odd because fuse is pulled)
and i have a dtc code. (which i think is due to the airbag issue) i will check tomorrow when it is light and not -4f. brrr.

truck starts and runs fine, minus 4x4 of course, gauges and the rest of the lights seem to work, stereo, 12v plugs, etc all seem fine.

no blown fuses that i can find.

Any idea what could cause all these items to malfunction at the same time?

on edit, just to be clear, this is on the 95 burb.
 
Did this all pop at once? Knowing the go to response is to check grounds but first I would check those "good" fuses with a multi meter to check for voltage. That's at least a warm thing to do along with a little research to investigate if they share a common ground point. I don't have 1995 manuals to check so hopefully someone more familiar with the 1995 and your issues will be able to chime in.
 
yup all at once. It was all working when i parked the truck. Started it up after work and this was what i found.

Also, add another symptom to the list: the glow plugs don't come on. (if i use my manual switch they work and the light turns on, but no automatic control on start).

I figure it has to be a power or ground common to the items, but i don't know what that would be.

I just did the engine grounds recently, but i will check them tomorrow.
 
looked through ground locations in turbine doc's faq and it appears these items are spread out over several grounds. I'll still check them, but seems unlikely that they would all fail at once:???:
 
well found a few ground points that were questionable. fixed them.

pulled 3 dtc codes.

29
39
41

12 did NOT flash.

problems still there.
 
DTC 29 - Glow Plug Relay Fault
DTC 39 - TCC Stuck "OFF"
DTC 41 - Brake Switch Circuit Fault

After looking these i remembered about a 2 years back when i first put this motor in i had a similar issue but it only affected dash lights and the gear indicator light. Cant remember exactly why it stopped.
 
Checked the fuses and they seem fine.

Checked in cab fuses to make sure they had power and they did.

So i think you are right ak diesel driver, bad ign switch.

No other suggestions?
 
yup i checked with a meter. about 11.9 with the the key on run (engine not on). a bit low, but i was just touching the neg probe to the dash cross bar. either way, it shouldnt stop things from working. i mean the blower would at least come on.
 
You have heard about "brown outs"? This is where the voltage is so low things quit working, motors slow down and burn up etc. Well computes signal 1 and 0's. 1 is "on" of course. Well if the voltage is low the computer could be signaling a "1" on but the voltage could be so low that it is read as a "0".

Check both batteries. Check positive cables including back to the fender fuse box. Clean that connection on the fender fuse box.

You want 12.6 for old batteries and 12.8 for new ones. Temperature dependent, but, 11.9 is indicating a high resistance connection or bad battery. Ign switches are well known on newer stuff to go bad like this. (low voltage.)
 
yes i have. most of these items are not digital though (could be wrong). for example the blower motor just receives a voltage not a digital '0' or '1' signal. or is it controlled through the comp? the rear blower works, and it gets the same voltage as the front blower.

Am i correct in assuming power goes through the cab fuse box and then through the ign switch to the different devices? If so the ign switch could have bad contacts and cause a voltage drop or no power through it.

Both batteries are about 2 weeks old. check the connections and power to the underhood fuse panel. all looks good.

That being said, the batteries were reading 11.99 volts which explains the low voltage at the fuse box. the alternator does put out 14v but maybe is getting worn out. also it has been cold here all week (-15c to -20c) and i dont have far to go to work, so maybe the batteries arent getting enough charging time on the drive. I put it on a charger for now. I'll keep an eye on this and see if the alt needs replacing once i get this dealt with.

I'm thinking i'll pick up a ign switch tomorrow and install it on sunday. seems the most likely suspect at this point. Although at 160 bucks :eek:, i really hope that's what it is.
 
WarWagon said:
You have heard about "brown outs"? This is where the voltage is so low things quit working, motors slow down and burn up etc. Well computes signal 1 and 0's. 1 is "on" of course. Well if the voltage is low the computer could be signaling a "1" on but the voltage could be so low that it is read as a "0".

Check both batteries. Check positive cables including back to the fender fuse box. Clean that connection on the fender fuse box.

You want 12.6 for old batteries and 12.8 for new ones. Temperature dependent, but, 11.9 is indicating a high resistance connection or bad battery. Ign switches are well known on newer stuff to go bad like this. (low voltage.)
Click to expand...

x2 on the above.

Ive had some wierd electrical issues like you described with battery problems before.

I would double check that in fact both batteries are good. I know you said they are almost new, but disconect them both, and load test individually. Clean the terminals and try again.

-Nick
 
well I'm disappointed. it wasn't the ign switch.

Seriously though, it fixed. You guys didn't harp on grounds enough. It's always a ground.:rolleyes5:

turns out when i checked the grounds, all the one i checked looked fine, i missed one. (probably the ground that gave me problems last time). There was a ground wire that i hadnt even hooked up tangled in the wiring harness behind the fuel manager. probably had been touching the fuel manager for the past to weeks just enough for things to work.

Everything works now. Good and solid. Now lets hope my ARP studs don't leak :thumbsup:
 
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