Dead 911 after alarm brain smokes

[85carrera]

so....

it all started with a desire to fix the cruise control. I did a little work and decided to check out the cruise control brain and I thought it was in the front trunk in front of the driver's side. So I see two mysterious boxes a black box with HOFCO III on the outside and a small white box. I disconnect the HOFCO box and take apart and realize it is NOT a cruise control brain...hahah...yes...you can make all the fun of me you want.

So I hook it back up and the car wouldn't start (turns over no gas) Didn't even sound like the fuel pump was turning on. I'm thinking great what the beep could it possibly be? It's obviously something to do with the HOFCO box (at this point i still don't know its an alarm system). So I start playing with the cables and I'm pretty sure I have hooked up correctly and then I get the red LED lighting up so I go for it. The car starts right up but then the box starts smoking!!! I quickly turn off the car and then the horn starts blaring!!!!! After waking up the entire block I quickly disconnect the alarm. Naturally I try to start up the car again and nothing. I take apart the HOFCO box and one of the chips is clearly burnt out. I did some research on the board here and I learned the HOFCO box is an alarm...

I'd like to just bypass as opposed to repair the HOFCO box. I never knew the car had an alarm on it nor do I care to have an alarm on the car.

Can someone please help me bypass the crappy alarm and get my car started and move it out of my friends driveway?!? haha...i was all dressed and ready to hit the town tonight but that clearly isn't going to happen!

[85carrera]

folks...quick question...

i have an 85 carrera.

trying to disable an alarm system gone bad.

is there a "DME relay" that provides power to the DME under the driver's seat? Or is power supplied directly to the DME? I'm trying to determine the difference between what is referred to on this board as the "DME relay" and the DME under the seat containing a huge beep plug of wires...

Thanks!

david

[ZOA NOM]

On your car, the DME receives 12v directly from the ignition switch. The DME relay under your seat provides 12v to the fuel pump. The Bentley shows a red wire from the Alarm Control Unit to the luggage compartment fuse panel, connecting to the top of fuse #2 along with the horn relay, power window and the fog light relay inputs. Your best bet would be to snip the input to the alarm control unit, which is shown as pin 30.

[85carrera]

well...im actually disconnecting a HOFFCO (sp) alarm system. my car did not come with the factory alarm.

so let me think of it this way. if the engine cranks but doesn't start, the alarm must be preventing the DME from turning on and thus keeping the fuel pump off right?

so rather than the alarm being between the DME and the fuel pump preventing ONLY the fuel pump from turning the alarm is actually between the battery and DME preventing the entire DME from turning on?

[85carrera]

so let me get this straight?

there is a black wire pin #61 going to the DME that powers the DME?

i don't have a wiring diagram so any help would be great....



thanks

[Joeaksa]

Just posted in your other thread. Email me your address and will send you a wiring diagram.

[85carrera]

just pm'd you

[85carrera]

so here's the deal fellas...hopefully someone can help me out.

im at my buddy's place in costa mesa, CA

i find a HOFCO alarm system installed....I unplug it and inadvertently plug back in the wrong way (I'm assuming). The car doesn't start....I plug it in a different way and the car starts, but the alarm box starts to smoke. I quickly turn off the car and proceed to pull out the alarm wiring harness.

after proceeding to pull out the alarm, my buddy and I soon realize the alarm affected the car in a few ways.

1. it received its power pretty much straight from the battery unfused (great idea)

2. there was a relay between the fuel pump and the fuel pump fuse controlled by the alarm

3. there was a wire to the horn relay

everything else on the alarm harness was disconnected or cut off.

my buddy and I removed the alarm wire harness including the separate fuel pump relay controlled by the alarm and replaced it.

now the car does not start. no fuel and no spark. however the DME is getting power. (we disconnected the wire harness to the DME and turned on the ignition and check each of the leads)

this problem is killing me. i have no clue what's going on considering the alarm really only had contact with the fuel pump fuse, so i don't think there's anything it could have really hurt. (the fuel pump still works).

hopefully someone has some insight because im about to give it up to a mechanic tomorrow and get charged crazy style. not good considering im currently laid off. sat night plans were already ruined and im supposed to drive to arizona tomorrow..

is there any way to test a DME? perhaps someone could cruise by and I could try dropping in my DME? that would solve a lot of headache cuz then i know its just the wiring...

any insight? i know no one likes wiring problems, but i could seriously use some help. so tear yourselves away from the football for one second.

go bears

david

[Early_S_Man]

David,

DME relays are always suspect in 3.2 Carrera no-start situations! Check under the drivers' seat for the date code of thwe existing relay. If original, plan to replace. In the interim, you could remove the cover and resolder both relays to the circuit board.

I suggest bypassing the the alarm system socket ... switched power to the 'extra' fuel pump relay you found.

After refurbishing or replacing the DME relay and powering the new fuel pump relay from ignition switched feed ... check at the #15 terminal of the ignition coil for +12 Volt power with ignition switch on???

Let us know what you find.

[nolove670]

what's the difference between the DME unit and DME relay? and do most people carry an extra DME relay?

[85carrera]

hey...

we actually removed the "extra fuel pump relay" and wired it directly to the fuel pump.

we even hard-wired the fuel pump running to see if it woudl start...no dice. obviously getting no spark....

so i don't quite understand what you mean when you say re-solder the dme relays to the board. are there relays within the DME that go bad and disonnect from the circuit board? or is the entire DME considered the DME relays???

thanks!
david

[mackskibum]

Is this a factory alarm?

[dentist90]

DME is the computer 'brain box' under the seat which controls all things related to the engine operating properly (fuel, air, spark timing, analyzing O2 sensors, temp sensors, flywheel position sensors...) while the DME Relay is the little black relay box beside the DME which switches power to the DME and the fuel pump. There is also a silver 'cannister' under the seat which is an altitude compensator (barometric pressure) sensor, which also sends a signal to the DME to adjust fuel ratio and spark timing.

[zrdstr3]

It's a good idea to carry an extra relay. I bought my 85 last week and the relay died on the same day.

[Early_S_Man]

David,

The DME relay has six pins and two relays inside the black plastic case ... click on the following link to see close-up pics of the board, relays, and bad solder joints:

PICS - Failed DME Relay

The DME unit is also known as an ECU or engine controller, and is located inside the large flat box ... it has two circuit boads inside.

[Joeaksa]

Originally posted by zrdstr3
It's a good idea to carry an extra relay. I bought my 85 last week and the relay died on the same day.

Anyone who has a DME car needs to have a brand new DME relay. Buy it and plug it into the system. Take the used one and put it in the glovebox.

You will need it sometime and be very happy that its there!

Joe

[911Urge]

Ive got one of those in my car as well. I hate it, the remotes are difficult to obtain and I am afraid to remove it. You may have to get it to a local alarm installer to get it properly de-installed.

Hofco still exists in So Calif. their website is http://www.hofcoalarms.com and they will talk to you if you need some assistance.

[Steve W]

Hofco makes a great alarm and the Hofco III is/was a high end alarm system. If you are in the Los Angeles area, and if you could have it restored, it would be best. They are active and located in in the Los Angeles area. The black box is the brain, and the white box should be a mic or shock sensor.

IIRC, the alarm disables the starter by tapping itself into the starter circuit at the fuse box. You should be able to see a set of black wires similar to the ones from the alarm harness around the fuse box area.

I think if your box smoked, you may have plugged the harness back in backwards. Usually unplugging the box should have disabled the alarm, and the car should start. However I suppose if wired differently, it could operate differently.

[85carrera]

my buddy and pulled all that crap out today....turns out it fired the DME relay.

[85carrera]

turns out the DME relay was fried. soldered right back up and the car runs.

buying a new DME relay off pelican parts right now...