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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: cwest on January 04, 2014, 05:24:57 pm
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Hello, all.
86' K20 TH400 4X4
Where and what size is the fuse that the ignition buzzer runs through? I'm pretty sure the previous owner pulled it (as I'm sure most guys do). I probably won't use it but would still like to know where and what size it is just in case I want to hook it up.
Also, I pulled the steering column recently in order to install a new pedal assembly and forgot to disconnect the battery. Needless to say, one of the wiring plugs sparked on something or other. Everything is back together now and the only discrepancy appears to be that the choke, parking brake, and high beams indicator lights in the dash now don't come on when I turn the ignition on. The dash light itself works, and everything else that I've checked, so that's a plus! I'm hoping that those three indicator bulbs runs on one fuse and replacing it solves things. Does anyone know which fuse that would be so I can avoid playing 'guess that fuse' under the dash?
Thanks for any info,
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All the appliances you mentioned are powered through different fuses.
- Choke Fuse powers the choke heater.
- Stop Fuse powers the key buzzer.
- Gauge Fuse powers the e-brake warning lamp.
- High Beam Indicator is powered through the headlamp and dimmer switches.
Check the high beam and park brake bulbs and socket connections.
Are you sure the key buzzer alarm module is installed? Along with the horn relay and hazard flasher, the alarm module plugs into the "Convenience Center" located above the accelerator pedal.
Power to the choke heater runs from the choke fuse through a two-prong oil pressure switch that's located either at the back of the intake adjacent to the distributor, or just above the oil filter. Make sure the switch is plugged in and not leaking.
See the 1986 Wiring Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Wiring/ST_352_86_1986_Chevrolet_GMC_Light_Truc_Wiring_Manual_CK_10_30_Only.pdf) for details; allow a few minutes for download.
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Thanks for the very thorough info. I'll check all of those things as soon as it get above negative degrees outside.
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Okay, I'm back from checking all of those things listed below. I replaced all of the bulbs in the dash, and they appear to be working now (well, all accept the red seat belt warning lamp). The choke light in the dash comes on now, and the fuse, as well as the two pronged oil pressure switch seem to be in tact. With all if that said, I tried to fire it up and I'm pretty sure the choke itself is not kicking on. The engine just turns over and over until the battery dies, and you can smell it flooding. I'm thinking now it's the choke itself and not an electrical issue. I had a friend tell me the chokes on these trucks are known to go bad, so that's got me wondering. I am by no means and expert in any of this and am pretty lost at this point. Any additional thoughts would be great.
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- Verify that the seat belt alarm module is plugged into the "Convenience Center" located above the accelerator pedal. The module controls the seat belt light.
- On a cold engine, the choke thermostat closes the carburetor choke plate when you initially depress the accelerator pedal about one-quarter or more of the way down. After the engine starts, 12 volts is applied to the choke heater through the 2-prong oil pressure switch (OPS) - and the choke plate gradually opens.
Your description suggests weak or no spark, grossly incorrect ignition timing, or a heavy carburetor float. Nonetheless, since you suspect the choke is the culprit, do the following:
- With the engine cold, step on the accelerator pedal one time to set (close) the choke. If the choke plate closes, the choke thermostat is doing its job.
- Turn the ignition ON, but don't crank the engine. If the instrument panel Choke light illuminates, the choke heater is electrically intact and grounded.
- Turn the ignition OFF and connect a temporary jumper wire protected by a 10-amp fuse or circuit breaker between the battery positive post and the choke thermostat terminal. Within 2 - 3 minutes the choke should gradually relax and open. Does it?
- No - replace the choke thermostat.
- Yes - the choke thermostat is okay. Remove the temporary fused jumper, reconnect the blue choke wire to the thermostat, and let the choke cool down. While the choke is cooling, verify ignition power to the OPS from the Choke fuse by turning the ignition ON, unplugging the connector from the OPS and probing the pink wire. Alternatively, if you don't have a test light or voltmeter, once the choke has cooled sufficiently to close again, unplug the harness from the OPS and jump the connector terminals. Turn the ignition ON. The instrument panel Choke light should go out and the choke should heat up and open again within the same 2 - 3 minute time interval. (Unfortunately, to easily verify operation of the OPS, itself, the engine needs to start and run...).
- Let us know what happens.
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Ok, I'm back.. I had a friend of mine come over and take look at it. We did a spark plug check and then got as far as figured out there is not power getting to the distributor. The ignition fuse is good to go so that's not the issue. According to my Haynes manual the ignition wire is pink? There is sort of a faded pink-ish/orange-ish wire going into the dist. I assume that's the old pink wire? However, under the dash there are multiple pink wires. There are two plugs on top of the steering column, one long one on the side, and one on the bottom. Do you know which of those set-ups hold the correct pink ignition wire? We also determined the ignition fuse isn't getting power itself so I'm hoping there isn't just a random break in the wire itself somewhere in the line. Anyway, I hope someone can make sense of that!
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I recently changed the pedal assembly over to a hydro clutch setup on my 86' Chevy K20. In doing so I had to unplug all the switches in and around the steering column as to remove the column itself. Since I put everything back together I'm now not getting any power to the distributor. There's power getting through the red wire to the ignition switch, but no power through the pink ignition wire when the key is turned to on. The ignition fuse appears to be in tact, and I can't find any obvious breaks in the system. Anyone have a good trouble shooting idea for this type of scenario?
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"The ignition fuse appears to be in tact"
Did you test this fuse or only look at it ? What have you done specifically so we can suggest things you might have missed, you say no power is on the pink wire when ignition switch is turned on, is the pink wire hooked to the right terminal ?
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I recently changed the pedal assembly over to a hydro clutch setup on my 86' Chevy K20. In doing so I had to unplug all the switches in and around the steering column as to remove the column itself. Since I put everything back together I'm now not getting any power to the distributor. There's power getting through the red wire to the ignition switch, but no power through the pink ignition wire when the key is turned to on. The ignition fuse appears to be in tact, and I can't find any obvious breaks in the system. Anyone have a good trouble shooting idea for this type of scenario?
The ignition circuit leg that powers the distributor isn't protected by a fuse. Rather, it relies on the primary circuit protection afforded by one of the fusible links at the firewall junction block, supplying 12 volts to the ignition switch via the large red wires.
Since you've already verified the red wires to the ignition switch are hot, try re-seating the harness plug at the ignition switch. If there isn't a connection problem between the plug and the switch, replace and adjust the ignition switch. But, thoroughly inspect the harness connectors and terminals that plug into the ignition switch for heat damage (melting/distortion) and repair/replace accordingly.
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I was reading up online and in my Haynes manual on the four sets of fusible links through the truck, but I couldn't paint a picture in my head about how they tied in with the ignition system. I'll give them a look-see tomorrow and make sure they're still in tact.
I attached a pic of the two terminals that go into the ignition switch. I inspected them pretty well and didn't see any burn marks or corrosion. However, now that I'm looking closer I think I might have reinstalled them wrong when I put everything back together. How are those two suppose to fit in the switch? Up and over the steering column with the blue plug furthest from the the firewall?
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Compare your image to the schematic on page 11 of the 1986 Wiring Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Wiring/ST_352_86_1986_Chevrolet_GMC_Light_Truc_Wiring_Manual_CK_10_30_Only.pdf). The connectors fit the ignition switch only one way. BUT, you must install the blue plug before the black one. IIRC, blue is closest to the firewall - but again it will plug up only one way.
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It's alive! As is usually the case the problem was a fairly easy fix. When I put everything back together the first time the prong in the ignition switch that connects to the ignition wire got bent down. In the picture below it's the prong that the screwdriver is pointing to, it's still a little bent but the plug eventually fit with some careful placement. If you look close you can see in the other picture a little indentation (upper right most area of the blue plug) where the prong was sitting outside the plug. Thanks for the help, guys, your suggestions led me to the answer!
While we're here though, and you guys are definitely experts! One more question while it's on my mind. Is it normal for the heater core hoses on these trucks to heat up to the point of almost being too hot to touch? I did the heater core last year, and am pretty sure I put the hoses back on correctly. Coming out of the firewall and heater core, I've got the hose from the top port going to the engine and the bottom port hose to the radiator. Is that how they should go, or should I reverse them?
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If your heater works I wouldn't worry about it. But the honest answer is the water supply (hotter side) should be stopped at the core's heater control valve before it goes into the core not after it comes out. Other than that I don't remember which hose goes where right now. CRS I guess. The core temperature will be as hot as the engine gets, however hot the thermostat lets the engine run at...anywhere from a cold 165 to a hot 210 degrees. Both of those temps are pretty warm to hot for most peoples tastes if they are touching them. Bath water is normally less than 120 degrees. There is another thread here somewhere about a core that cools down when the radiator cap is put on...it has some good info in it.
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Our trucks don't have heater control valves from the factory. Heater hose temperature should be nearly the same as engine thermostat temperature, ~195° F. The 5/8" heater hose connects to engine, the 3/4" heater hose connects to radiator.
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Sorry, when did that happen? Seventies trucks had them, I guess the '80's trucks relied on damper doors, bypass ducting, and insulation to keep the heat out of the cab?
I was thinking the same basic setup made it all the way to the metric trucks. My 78 had a heater flow control valve at the core cover on the firewall. My '75 outside had A/C and it does too (have a flow valve) but that doesn't make it factory I guess.
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I believe the only trucks that had OE heater control valves were the Suburbans and Crews with rear heat and AC. The C/K standard cabs relied entirely on temperature door position; all the heaters were constant flow.
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Oh crap, That was completely wrong information on my part. I just went out and looked at my truck.
Sorry all, I'll be sure of any information instead of my poor memories before I open my mouth again. :-[
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So it sounds like I'm good 2 go on the heater hose temp. I'll just leave them alone. I would also just like to acknowledge that this is my first discussion thread that made it to two pages! Haha, thanks for all the good info, guys!
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Well...some of it was good anyway LOL ::)