no power on accy

Car: 1993 Acura Integra LS

Issue: No 12v on radio accessory lead. Yes, there IS Accy power from ignition switch to fuse panel.

Troubleshooting: Used DMM to find any opens from the stereo to the underdash fuse panel. All associated fuses are good. Found that there's NO power coming from the "radio" fuse. Not sure how to troubleshoot this other than trying to remove the fuse box itself.

Help!

is there power present at the radio accessory fuse with the fuse removed?..one side should have power. do the terminals for that fuse look spread/wider than other fuses?..careful prying with a dental pick style tool will allow the terminal to contact the fuse. if you don't have continuity from accessory feed to the radio fuse, the fuse box has issues.

There seems to be some inconsistant information about this car on this site. The switched 12v Accy lead from the ignition switch is WHITE/ Red. Not Yellow or Yellow/Red. And there's no power coming from it. I'll have to take it apart and investigate.

have you tested for voltage at all of the fuses(both sides of each fuse) with the key in the on position? sometimes its not just the fuse labeled for the radio or acc, it could be some other fuse that looks like it wouldnt have anything to do with the radio, maybe the fuse for the 12v outlets...?. if all else fails then i would just run a new wire to the vehicles accessory wire at the ignition harness.

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Yeah I've looked at an electrical diagram of what circuits the radio is using. I'm not an electrical genius but I was able to understand a few things. It's rather simple, actually. I've tested both sides of the fuse and terminals they connect to. Everything tells me that it should work IF there is voltage on the WHITE/ Red wire, which there isn't. So, I put a jumper to the Yellow wire which was right above it on the same connector and the radio works. Not the solution I wanted but it confirmed that it was the ignition switch at fault.

I tested for continuity from the WHITE/ Red wire going back to the switch and it was fine. There just is not any voltage coming out. I took apart the switch and clean the contacts and applied dilectric grease but still no dice. I'll just have to replace it. Bummer.

are you sure its not the plug that goes into the ignition switch? sometimes they can lose contact over time because of heat and vibration warping the plastic around the pin causing the pin to wiggle free.

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The ignition switch on these cars are 1 piece. Meaning that the wires are soldered onto the ignition switch itself. Think of it as a stereo with a built in wiring harness lol.

The wiring from the IG switch to the fuse panel is good. There's just not any voltage.

broken solder joint? either on the wire in question or the 12v input wire that feeds it. im sure you'd want to test all possible minor issued before you spend the money on a new cylinder. even though you are probably right about the cylinder being bad i think its worth checking even the unlikely possibilities.

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is fuse #25 (40A) underhood ok? that fuse feeds both the blower motor (IG2-B) and accessory (ACC) circuits through the ignition switch .

Interesting. I see that in the schematic I have but I can't locate that fuse in the underhood fuse box! It's not even labled on the fuse box.  How strange...

EDIT: Actually #25 is under dash. I just replaced it. No dice.

did the fuse have power present on one of the terminals for it? one side should be battery power, the other dead. test the dead side for continuity to the ignition switch. test the blue/white at the blower motor for power...key on of course. ground the blue/black at the blower motor with a jumper lead, does the motor spin?

I went through the flow chart as described in the service manual. No 12v to the blue/white at the blower motor. I also tested for 12v at the solder joint on the ignition switch itself which didn't show any output.

so assuming we are looking at the same manual/diagram, you have no power on IG2-B nor ACC. is there power at BAT-B? if no, is there power at the No. 25 fuse? if there is and not at BAT-B, you need to test for continuity between the non-powered terminal of fuse 25 and BAT-B. of course, make sure the fuse is good also.

I'd suggest my normal fault finding technique - ROTATE all same rated and type fuses. If a single non-matched fuse, then replace (rotate) with a spare.

Then try circuit tracing etc.

In response to concerns raised by another esteemed the12volt contributor...
I've briefly looked at a basic diagram (autowiringmanual-199093-honda-integraacura-integra-wiring-diagram).

That shows the ACC being on the same "Bat-B" IGN-switch circuit as the Blu-Wht IG2-B circuit which I take as being the heater.
(The other IG-switch Bat-A circuit is Wht-Blk circuit via 50A Fuse #32 and is for IG2-A, IG & STart.)

That ACC circuit is from the Wht-Red power via 40A fuse #25.

If the IGsw solder joint for the ACC is NOT +12V with the key in the ACC position AND an intact 40A fuse #25 (ie, +12V at the Wht-Red solder joint), then that switch is faulty (burnt out else worn) in which case the Blu-Wht IG2-B joint for the heater will not be +12V in the IGN position.

If burnt out, the question is what burnt out the switch? A 40A fuse or circuit breaker could be wired direct from the battery to test the Blu-Wht IG2-B heater operation.
If that blows, then there s a heater fault. That circuit could be disconnected until the fault is found.
But it may be mere age that has blown that switch contact. Contact surface contamination increase resistance over time, hence heat and eventual destruction.
Personally I don't like any switch to carry more than a few Amps. I have removed many such loads from my OEM (1965 vintage) switching via relays (eg, IGN via a relay, full current carrying headlight switches & dippers switch relays instead, etc).   

Heater problems may be a shorted motor, or motor speed dropping resistors (usually wire coils in the fan path) shorting to GND.


It may also be a high ACC loading or a short that has caused switch burn out.
In both cases, the 40A fuse should blow. But repetitive replacement or use of a higher rated fuse could have cause IGsw damage. (As well as the aforementioned "high current" and age issues. I often feel for switch and connector heat to ascertain their health. But be warned - burns are not uncommon!)


Another aging or "current overrating" consideration is connector elasticity - ie, fuse terminals and female contacts can be heat effected and lose contact pressure. Both male & female connectors can lose conductivity due to heat effects.


The above is a somewhat limited reply. I don't have the complete wiring diagram (my torrent is slow...) but wanted to add some considerations or tests before a new switch was fitted etc as well as suggest a testing order.


Otherwise your testing method seems fine - especially now that I know what circuits you and Ween are referring to.
FYI - I was concerned about the somewhat large 40A fuse for ACC, but now I know that is fine. (Not that I know the vehicle's history - ie, when problems occurred, and if anyone has used a 2" nail (>40A fuse) for that circuit.)   

Thanks guys. I'll check ASAP. I know I measured one side of #25 fuse and it did have 12v. I didn't bother checking the other side :(

Oldspark! The 40a fuse IS blown! I'm going to wire the heater fan/blower directly to 12v and see if it turns and continue to follow the troubleshooting flowchart in the factory service manual. Thanks!!

To help find a short, instead of blowing fuses (if you don't have a circuit breaker), you can use a light bulb in place if the fuse.

While the short or heavy load exists, the bulb lights.
A big bulb (eg, headlight - with due care handling halogen bulbs if relevant) will only light for heavier loads or shorts (above a few Amps).
That's a very useful technique for intermittent faults - the bulb lights when the short occurs, eg with suitable switch positions; jiggling wires; or vibration and bumps.

[ Circuit-wise that's like 2 series resistors. The bulb is the first and lights if the 2nd (the load or short) is of similar or lower resistance, and it limits current to the bulb current - eg, if there is a short to GND, the bulb is "powered normally" from 12V. No loads or light loads likewise limit the current thru the bulb, hence it's dim or off.]


Other than judging brightness levels etc, it doesn't show what the actual load or fault current is. That requires a big ammeter or for large currents above a DMM's normal 10A limit, a shunt and voltmeter. The bulb can act as a shunt (though halogen bulbs are quite non-linear wrt voltage versus resistance).

PS - I had assumed that the fuse was ok and had blown again. Ween questioned the fuse status a few times, and that's where I butted in with my common tip. [Fuses are usually the first check. However many fuses seem to be ok but aren't, hence my experienced learning where I always ROTATE fuses AS WELL as checking the fuse(s).]

But in your 2nd last reply, you didn't measure the downstream side voltage (which should always equal the upstream side of the fuse, though if that's 0V, then it is not getting power...).

If it's a one-off blow, then no big deal. It's if it reoccurs that all the writing in this thread should be useful.
It it is a one off, then this should be 3 post thread - no power; check fuses; 40A fuse blow - thanks!
And do not take the last sentence as any form of sarcasm. This forum is to help people and that includes people that know nothing about cars or electrics or that fuses exist etc. And boy oh boy, even I have had multi-pagers for threads that should have been 3 post threads!

LOL yeah I know what you mean, Oldspark. My Alarm thread was like 17 pages long! Haha! I still go back in there to recap everything I did. Good info around here!

Anyways, I took apart the blower motor and the entire thing was seized up. It took a lot of force to turn it. The connector to the wiring harness was starting to melt also. Yes, potentially dangerous. I tested the resistor as well and it was out of spec, so I'll need to replace that as well.

Thanks again for that circuit diagram. I now have a clear understanding of how this works!

Thanks. Diagrams can be hard to find. Sometimes I search and find paysites etc but might persevere and eventully strike a brilliant site. (A recent search to get some info for my brother's mate's RX7 found a site with all(?) RX7 models and their Manuals downloads - mechanical and electrical, all year models.)


Glad you found the problem. Glad too it was a possibility predicted by someone...
Yeah, this is a good site eh?!


Hopefully this is another example how problems must be stepped thru in a logical order, but I suspect you figured that out once you had the diagram etc. (And never assume good GNDs or fuses or even battery connections...)
Alas my replies tend to be long because I foremention the possibilities up front. That's bad from a confustigation point of view. Ween OTHR took more of a step by step approach ( - cum elimination) which is the proper way to do things though it can mean many small replies & iterations, but that usually less confusing (maybe with the expense of more replies).


Happy accessorizing!


PS - BTW - seized or seizing motors are often a cause for over-currents and fuse blowing etc. So too worn motor brushes. (But NOT air-blocked fans etc - they normally reduce current!)
Glad the fuse blew before the connectors etc melted and started a fire, or smoked occupants to death. (READ: Glad nobody uprated the fuse to a 2-inch nail etc!)
Again, that is a good example of my suggestion to check wire & connector and switch warmth on occasions as a preventative maintenance measure, or as a tool to finding problems.   
It's also a good example of when - or why - not to uprate fuses etc.

Check the condition of the melted wires and contacts. Contacts can lose elasticity or corrode and hence heat up and flame etc. (Such faults do not always blow fuses. In fact like arcing faults, rarely do the fuses blow.)

Some warm or bad contacts an simply be fixed by breaking and making the contact to break thru contaminants etc - ie, disconnect and reconnect all contacts. (That's why some fuse checks fix problems - the remove & refit is the fix - and novice fixers are left totally confused as to how they fixed it. Else witnesses think us repairers have spiritual powers.)