Electrical Mystery

[Crazy Lucy]

Help! Our mechanic thinks our '90 GW is possessed! Can anyone offer some insight for what to tell the mechanic to look for - he is stumped! (And keep in mind, I am a total idiot when it comes to auto repair - so keep it as simple as possible - speak slowly, use small words! :) Quirk: When you accelerate from a complete stop ONLY, the radio loses power (doesn't cut out totally). Now here's why this confuses us - it can't be a connection, you can take this thing over the meanest dirt roads, bumps, etc and the radio stays solid, and you can accelerate hard on the highway and no loss in power. I know the radio is fairly insignificant, but my concern is that this is the indicator of some larger electrical/power problem (note, we had the whole Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley thing rewired - the wire bundle in the drivers' side floor is all practically brand spanking new). Any thoughts? Also, electrical in nature the switch to after-market air conditioning seems to have given up - should I just give up on it (it gets hot in Maryland!) and is there any weird chance the two are related? And one last strange electrical thing, the reverse lights keeping dying. Does anyone know if by chance these things could be related? Any insight at all will be so greatly appreciated! Have a wondeful holiday weekend!

[JDJeep98]

They may be related. It sounds like you may have a bad ground. There should be a ground strap between the body and the frame somewhere. Check it for damage or corrosion.
The reason I'm going there is the acceleration issue. The stresses on the body mounts could cause the body to shift slightly aft when you accelerate from a stop (where your G forces would be at their greatest) possibly causing a shift in the grounding strap and agrivating an already marginal connection.
Anyway, I would start there.

[ September 01, 2003, 07:59 AM: Message edited by: JDJeep98 ]

[woodybeone]

Welcome.
Can you be more specific to the after-market air? Is it using the same rotary dash switch as the factory unit ? What was changed /added to from the original system?

The reverse light problem could be associated to the trailer hitch wiring (provided you have a factory hitch). There is a relay box that plugs in series with the rear lights to provide signal to the "horse trailer" wiring connector. Parts(relay) do fail in these but can be repaired.

The radio issue is strange. Will the radio loose power(no sound and no display), or just loose sound (display still lit)? How about when a tape is playing , same result?
Agree it could be a loose/failing ground somewhere in the system.

Why was the wiring harness replaced? How much was replaced? Where did the replacement harness come from ?

[Crazy Lucy]

Hmmm - the grounding issue makes a lot of sense - it does not lose all power, the display lights on the radio dims, (and does the same thing with tape or radio in operation) but does not cut out completely. However, there is one good thing that has resulted - I tend to be a bit heavy-footed on the gas off the line and this is modifying my behavior to be a gentler driver!:) I will have our guy check the ground right away (as I would think a bad ground could also cause other issues down the line, no?). Thanks for the heads up! As for the AC issue - I really don't know what else has been changed/added. It uses the in dash switch for factory air, and it works, occasionally and when it feels like it, other times, nothing (no rhyme or reason there- hence the "possessed" moniker). I will certainly look into the wiring for the hitch relating to the reverse lights - as we do have a hitch with wiring. As for the wiring bundle, there is a huge mass of wires that run on the floor at the drivers' feet - ours (upon purchase is May) was FRIED (had all kinds of electrical failures and misfires) so they cut out all of the fried part (mechanic was surprised the Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley thing hadn't caught on fire yet!) and hand re-wired the entire bundle and re-wrapped it all. We haven't had any of the old issues that neccessitated that repair (really fun stuff like the car being able to start in Drive, lights not turning OFF, etc.) All of the insight you guys have provided is wonderful - I so appreciate it!

[Joe Guilbeau]

I believe that you are looking at several un-related issues.

Issue No. 1...When you accelerate from idle (stop) the radio volumn is not steady.

Theroy: This is an indication of the alternator not coming "on line" right away and providing enough power to run all of the circuits involved. Alternaors will have a lag time for the magnetic field windings to send out power when the regulator senses that there is a need. You need to re-route the "voltage sense" input to the alternator to get a bit more downstream than where it probably is.

Solution: See if the sensing voltage routed to the regulator circuit on the alternator is going to the battery or the starter solenoid. If it is, try sensing the voltage at the "big splice", and use enough of a 18 AWG length to drop (IR loss) about a volt from the big splice to the connector on the alternator. If this solves the radio problem you can move on to the next issue. Cost? A length (3-6 ft) of wire.

Analysis of why this could be the problem? This is only happening when you are at a stop, therefore the battery is telling the alternator that there is plenty of charge, and that the battery is in a fully charged state. Therefore the alternator regulator circuit is shutting down the field current (to test theroy, put screwdriver tip against alternator to test magnetic field being generated). When the FSJ is floored with the radio on, the vehicle draws more 'juice" than the battery can supply, and therefore the radio outputs less volumn, and the alternator "kicks-in" now that the RPM's are of sufficient amount to "turn on" the regulator. At speed the alternator has enough RPM's to energize the magnetic field, and power keeps up with demand.

Check the alternator and let us know if it is a Delco 12-SI, check further to see how many wires are connected (three wire, two wire or one wire).

Let me know and I will help out with the troubleshooting. To further test this theory, turn up the volumn full blast, then at very modest volumn to see if the alternator can keep up with the radio amplifier power requirements.

Issue No. 2: Air Conditioner problem...need a much more refined problem description than what was provided.

Issue No. 3: What exactly happens to the back up lights? Do you hit a tree and break them, does the fuse blow? Do the lamps burn thru and open up?
perhaps you could convert the lamps to Buddhism, and get 10,000 lives out of them before "dying".

Just a little humor to lighten the mood, eh.

Really, we are here to help, just help us with a more complete diagnosis of the rear light problem...

[Crazy Lucy]

OK - I will have the mechanic clense the reverse lights chakra and aura in the morning! :) That made me smile - thank you. Reverse lights - they didn't work when we bought the car and it was a simple fix - re wiring that bundle at the drivers' floorboards fixed all the issues at once, but now they are kaput again (have NOT checked the bulbs yet, as what are the chances both would go at the same time?) Don't think it's the fuse as turn signals are on same fuse and those work fine.
Wow - the electrical issue with the radio seems very complicated. I do not know what type of alternator we have - and to be quite honest - I don't know if I could even FIND the alternator if asked! At least I am honest! I will print out all of your suggestions and just hand them over to the mechanic with the keys in the morning! Both the grounding theory AND the alternator power theory make a lot of sense - I will absoluetly let you know what it turns out to be...
The air condition has got to just be the relay switch - it worked fine just now on the way to the store, but didn't on the way home, so the unit itself isn't the issue (I had my son watch the condensor while I jiggled the slide switch about a thousand times - if it wasn't broken before, I'm sure it is now! Please note my extremely hi-tech way of approaching problems - couldn't get it to fire up, then I got in a day later, and it turns right on! Possessed I'm telling you!
As a newcomer to your little society, I am hooked! The 'support system' I have found is wonderful and I feel much more confident that we can overcome the little glitches with all the help you all offer so generously! We sooooo love our GW - and so does all of Baltimore! We can't go anywhere without meeting strangers compelled to come over and talk to us about the car (or try to buy it - it may have quirks but she's a beauty!) Thanks again for all the help - and the humor - my Buddist reverse lights! :)

[2Stock]

Just a note to say why I think Joe G is right about the radio:

Not too long ago I decided to cruise down the highway to a few of the small towns around the DFW Metroplex. After I had been about 40 miles on the highway, I got off and drove around in the town. I turned on the radio and, basically, the same thing happened: it did not play when I accelerated and it did when I was idling. I started watching my voltage meter and it was not charging. That is when I suspected that my alternator was bad. I drove home on battery power. I replaced the alt. and all is well again.

[JeepBountyHunter]

Tell us what kinda Jeep your driving? Year etc...got pic's :D

[Crazy Lucy]

Oh boy, I'm sorry - we are enjoying life in a 1990 Grand Wagoneer - absolutely pristine, spent her life in Texas, as a matter of fact (rude awakening come wintertime here in Maryland!) As for a photo - I cannot for the life of me figure out how all of you post your nifty photos - got some great digitals of the car, but feeling very net ignorant right about now...

[Joe Guilbeau]

Here ya go!

http://209.238.200.129/gw/elec/GW_wiring-1990.html

Looking at the Charging System diagram, it indicates a classic wire up of a Delco 12-SI Alternator...

Here is a section of an article that I am writing on the subject matter:

Section 2…”Typical FJS Jeep Alternators”

Delcotron 10-SI Series alternators. These were the 1st generation of Delco/Remy System Integral (“SI” meaning that the regulator was mounted inside the alternator, instead of on being a separate unit on the firewall), and began showing up in the very early 70’s in GM products and weighed about 10.5 lbs.

With all OEM components installed they had outputs of 37-amp, 42-amp, 55-amp, 61-amp, and 63-amp ratings, outputs higher than 100 amps can be purchased but the heat and cooling requirements required are just not incorporated into these units and therefore are not recommended.

Cooling was accomplished via three vertical slots on the rear housing and a pulley mounted cooling fan. Again, the threaded mounting hole and orientation of the regulator connections determined the “clocking”.

Amp’s/RPM’s
0 amps at 1000 alternator rpm
32 amps at 2000 alternator rpm
63 amps at 6000 alternator rpm

Delco SI-series internally regulated alternator has the following connections.

One large connection that is the Alternator output, known as the Bat, this connection has "Bat" cast into the housing (aftermarket housings may not incorporate these markings).

Two tabs to connect a Molex connector to, these have "1" and "2" cast into the housing next to them, these tabs are inputs to the internal regulator.

"1"- this terminal (usually closest to the "Bat-terminal") is fed from the Ignition thru a lamp ("idiot light"), and is used to supply the magnetic field inside the alternator with the voltage needed to operate.

The lamp limits the current flow to the "Field" terminal, and this current limited voltage is what tells the regulator to start/continue/stop charging. When the alternator begins to charge, the voltage increases at the battery, therefore the voltage at the ignition "Run" terminal switch position increases.

This increase in voltage eventually reaches a point (as the alternator charges the battery) to where it is equal to the field voltage inside the alternator. Thus they equalize out, and there are zero volts across the lamp. Therefore the lamp goes out, and the voltage being fed to the "1"-Terminal is essentially 0Vdc.

When this happens the field collapses and the alternator stops charging. The idiot light is there to detect under voltage and over voltage conditions at the battery. Either of these conditions will energize the "idiot" light.

"2"- this terminal can be fed from the positive battery post or the starter solenoid where the positive battery post connects to the solenoid switch. This is an input to the alternator that also senses the battery voltage, some regulators use this and some do not.

"Bat"- this terminal is for the alternator output to the battery. On most jeeps this output goes to the ammeter inside the cab, and returns and has a fusible link in series somewhere along the line.

That is about all there is to it, in the most simplistic terms.

For a bit more on the regulator circuit...

The Number two terminal is connected to (most likely) the solenoid terminal hooked to the positive post of the battery, or is set up a for remote sense, and connects to the braised or soldered fan-out connection, and senses the charge condition at the battery, and routes this voltage to a voltage divider network with a capacitor to filter it, inside the regulator circuit inside the alternator itself.

The voltage divider feeds a Zener diode, that is "off" (while the alternator is putting out a charge), when battery voltage reaches a threshold, the Zener turns on and provides a 1st transistor with base drive. This 1st transistor controls a 2nd transistor that is used to turn "On/Off" the magnetic field or the rotor.

When the 1st transistor turns on, it grounds the base of the 2nd transistor thru a diode. Thus the 2nd transistor is turned off.

This 2nd transistor is responsible for providing the voltage that the rotor's magnetic field needs to maintain itself.

So, the magnetic field collapses, and the process reverse itself. The 1st transistor now has a decreasing voltage (recall that it is fed from the battery) supplying the Zener diode and as the voltage at the Zener diode falls below a threshold level, the Zener "turns off", or more correctly stops conducting current.

This, in turn, limits the voltage to drive the base of the 1st transistor, which in turn "turns off".

Thus, there is no longer a ground at the diode feeding the base circuit of the 2nd transistor.

With the base of the 2nd transistor reaches a high enough voltage the 2nd transistor turns on, and it's collector voltage now feeds voltage to the rotor and the magnetic field is once again up and running.

The alternator generates voltage and current.

This happens over and over...energizing and collapsing the magnetic field thereby controlling the alternator output, it is a wonder that these alternators last as long as they do.

Delcotron 12-SI with 6 cooling vents…these were available in 56-amps, 66-amps, 78-amps, 94-amps,

The cooling fan on a Delco 12-SI alternator is easy to spot, as it backs up the alternator pulley and is black thermoplastic with a metal plate attached between the fan and the pulley for added strength. These models began appearing around 1983. With under hood real estate becoming a premium and greater electrical loads making demands on the alternators, the 12-SI with it’s increased cooling and higher output became a popular component. Larger air intake ports on the rear of the alternator also contributed to cooling. These units can be purchased from aftermarket vendors up to 140 amps. The interior and cooling components incorporated in these units make this feasible.

0 amps at 1600 alternator rpm
30 amps at 2000 alternator rpm
70 amps at 6000 alternator rpm

Improvements in the regulator circuit have occurred but the operation is basically the same as in the 10-SI Series.

Have fun...

[bigun]

Man you guys missed the main problem this is a Texas truck in shock after having been taken Maryland the poor thing is screaming for help suggest she find a good automotive Psyc. doc. to get the poor thing to talk over it's problems also suggest finding good witch doctor to do rubber chicken thing

[Crazy Lucy]

OHMYGOD - I am laughing my behind off! Yes - it is surely in shock!!!! That whole electrical explanation thing was SOOOOOOOOO far over my head I can't even tell you where to start - does it tell you anything that I didn't even know where the alternator is let alone anything about how it works, etc. - and fellas - let me tell you a little secret - the only reason I passed high school physics (the very LAST science class I sat in to date) was by out and out cheating my way through! It's hopeless. But - to bring some of the mysteries up to date - the mechanic took a look-see at her today - the AC issue is a plug fitting in the engine where the condensor unit plugs into the coolant line (it actually looks like a household plug...anyway...) it's not the dash switch - and he showed me how to check it if it does it again, and then he'll just swap it out - for now he just tightened it up a bit and it seems to be running fine. The reverse lights - loose steering column/stick not sitting in the right position to trigger the reverse lights (jiggling it flicked them right on) which gives me just the excuse I was looking for to put in the nice wood steering wheel I wanted - anybody know a good source for that (also want a nifty wood knob for the end of the shifter). The radio is still a mystery - I'll keep you posted on that. I do now know it is an "after market radio" if that helps any...thanks again for all of the advice - and the laughs!