Omni GLH electrical problems

[iTurbo]

My Omni GLH Turbo started acting up lately. The charging voltage will drop down really low all-the-sudden and it will start bucking and the tach goes nuts.

I'm getting a code 47 (charging voltage too low), but I'm also getting other strange codes that aren't being saved. If I watch the 'CODE' parameter on my OTC 4000E, it will flash wierd codes like "FF", "C1", "80" etc...but they are not saved and only appear momentarily. Also, EVERY data readout on my OTC is freaking out! All the sensor voltages are going nuts; TPS, MAP, knock sensor will suddently spike to +5v, coolant will momentarily show 280F degrees etc, and I get constant KR on all cylinders, even at idle!.

The car is running on '89 SMEC electronics from a turbo Caravan. Is my SMEC shot or what?? Another wierd thing is that the OTC will suddenly quit while driving and say 'NO DATA'.

[MiniMopar]

You've got a grounding issue, it sounds like. The electronics ground at the fuel rail bolt. Make sure the ground strap between intake manifold and the firewall is in good condition. Also check the ground at the front of the head.

[iTurbo]

So far I've tried checking my gounds. All look good, clean and tight. Battery terminals are clean and tight as well.

Grounds I checked:
braided strap from back of intake to firewall
large ring terminal from fuel injector subharness to rail mount bolt
negative battery terminal to inner fender
large ring terminal from front subharness to front of cylinder head
ground on inner fender behind SMEC
another ground from inner fender behind SMEC to cylinder head ground
clip-on braided strap from solenoid band to inner fender

I did find one broken ground wire that is the brown/yellow wire that grounds to the trans case. This was originally going to the neutral safety switch since the underhood Caravan harness was auto. Since my GLH still has A525, I cut this wire and grounded it like the manual harnesses are configured.

Still nothing has changed. It will intermittently charge and the battery voltage at idle will go up to ~13.6v, at which point everything seems great! Then it will stop charging and the battery voltage will drop down to ~12.2v and everything starts acting up again. I cleaned out all the connectors I could and looked for broken wires....moved the harness and connectors around with the engine running and it made no difference.

The alternator connections are tight, but with the NPR in the way, I cannot verify field voltage. Could it be as simple as a bad alternator?

[iTurbo]

I also tried a spare 2.5L TI SMEC (from an '89 Shadow ES). No difference compared to the '89 Caravan TI SMEC I have been using.

I'm going to rip out all the intercooler plumbing, remove the front subharness and verify it's 100% OK, and then have the alternator bench tested.

I have a feeling it's something in the wire harness though. The car was doing the same thing about six months ago and it miraculously cured itself. Now the problem is back.

[tryingbe]

Check the voltage sensor wire at both end.
My somehow bended itself at the computer end and caused the voltage go low.. Took me a week to figure it out what was wrong.

[iTurbo]

Yes I'm definately going to scrutinize the alternator field wiring very closely. When I constructed the front engine harness, I used too much friction tape. Would have been OK, but my oil pressure sender rupturned recently and coated the entire front of the engine bay with oil. Everything is all gunked up with that oil/tar mix; what a mess.

I removed the front engine harness today and didn't find any obvious broken or chafed wiring, although everything is extremely dirty.

[MiniMopar]

Yeah, the thing to do is find out why the power is sagging so much. If the alternator checks out, start measuring the voltages going to and from the power module. I mention what to look at here:

http://www.turbo-mopar.com/forums/sh...6&postcount=16

[iTurbo]

I had the alternator bench tested today....no workee.

Replaced the bad 90 amp ND with a 120 amp ND and everything seems normal again so far. I did find a chafed wire that was for the HEP. I think it was randomly shorting out against the frame which is what was causing all the sensors to freak out and causing all the bucking.

[iTurbo]

Russ, that picture in your sig is going to give me recurring nightmares...

I got the car fixed and it ran for....oh about 30 seconds at which point it shredded the belt. It my hurry to get it fixed, I didn't properly align the alternator pivot sleeve.

Turns out I can't use the 120amp ND alternator anyway. I've relocated the radiator 3" towards the passenger side (to accomodate the large NPR IC) and it's right up next to the alternator now. The 120 ND is physically larger and if it was properly aligned, the field terminals will hit the radiator end tank! Good grief.

So today I have to swap out alternators with my Shelby Lancer which does have the 90 amp unit. Sometimes customizing your TD can really turn around and kick you in the ---.

[magtec]

i'll give you an alternator in exchange for the shelby lancer.

[iTurbo]

I would but it's rust free!

[SL#63]

I would but it's rust free!

In that case...I'll swap you my rusty alternator for the SL

Keep us posted on your findings (I'm about to start looking into the charging issue with the SL I just bought, so any references will be appreciated!)