[LA1995classi]

My 95 LWB has an intermittent problem that I can't solve. It starts with a whine through the radio that seems synced with the RPM. When this happens the truck will sometime "go dark" for a second or two when driving (lights, gauges, tach drops dead) and then come back alive quickly before the truck stalls. The truck continues to run until after stopping. After cutting the ignition it goes into lock out mode (no power to anything but the clock, radio needs to be reset). The only thing that fixes this is removing the neg and pos battery connections for a minute or two. After doing that the truck starts, idles well, and runs great for a day or two or even a week or so before this happens again.


Things I've done (and yes, I do have RAVE):
replaced the door actuators
replaced ignition module and coil
replaced battery
had alternator tested
removed radio to inspect the connections and wires<br>removed, cleaned all the connectors I could find under the bonnet<br>removed and inspected the connections of all fuses and relays
removed and cleaned major ground points
replaced IACV (twice)
New dist cap and rotor

Because this is an intermittent problem and the whine through the radio sometimes seems to start after hitting a bump in the road it makes me think there is a loose connection somewhere. I haven't been able to find it and don't understand how unhooking the battery would solve a loose connection.

Am I missing something simple? I've combed this forum for months and haven't found an answer.

 

[LA1995classi]

Thanks grnole. I tested the battery and alternator myself this morning. The battery tested at 12.1 volts and the alternator was putting out just over 14.1. I did a negative drain test and it showed about .1 volts which supposedly is fine. I've heard a bad diode can cause problems with the electronics even if the alternator appears to be good. 14.1 is on the weak side of good from what I've read but it's still putting out a charge. I think the 12.1 volts on the battery seems low. The battery is only a few months old but I may try to exchange it under warranty before doing the alternator.

 

[LA1995classi]

Still have the stock stereo. Minus the whine it still sounds good.

 

[LA1995classi]

Ok, the alternator was bad and I replaced it. Everything was great for three days and then the problem came back. It starts with a whine through the speakers and ends by going completely dead after I turn the key off. The new alternator is putting out 14.6 volts and the battery is now showing 12.6 volts.

Sometimes everything comes back to life after a few cycles of the ignition key but disconnecting both battery terminals works every time.

Because the truck is going into disable mode it tells me the alarm system is in play. Is there anything else that would cut power to everything but the clock?

Tomorrow I'm going to pull the two fuses that lead to the alarm and see what happens.

Has anyone else had something similar?


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[LA1995classi]

I disconnected the alarm unit plug and jumped wires 1 and 2 so the starter works. Started it and everything was fine until I put it into gear. It died and locked out again.

What, other than the alarm ecu can immobilze everything? Everything is dead. Dome light, dash, radio goes into reset mode. I disconnect the battery pos and neg, reconnect, and it all comes back to life?

With the alarm out of the equation, I'm now stumped. I should mention that when this happens I have power to both sides of the main fuses in the engine compartment. I thought about the gear selector switch but would that cause a total lock out? Is there a relay somewhere that could be causing this? Maybe disconnecting the battery resets the relay? Would the fuel inertia switch cause a total power lock out? I thought it just cut the fuel pump.

Does anyone have any ideas?

 

[LA1995classi]

Thanks Jonno. I've spent several hours going through the RAVE wiring diagrams. I must be missing something. It looked to me that the alarm was the only thing that would cut the power to everything and cause the radio to go into reset mode when the power came back.

The next time it happens I'll poke around with a multimeter to see where the power stops.

 

[LA1995classi]

Ok, I think (knock on wood) I tracked it down to the alarm relay. After pulling it the truck is running great and I've had no stalling or lock out episodes. I tested the relay and it seemed to be ok (clicked when I put a charge on it) but if it was sticking shut intermittently it may explain why hitting a bump would trip the relay and turn the alarm on while driving. It may explain why disconnecting the battery solved the problem temporarily if doing so opened the relay again. I had a headlight wiper/washer relay on my P38 that would stick and spray washer fluid until I pulled the relay or the reservoir ran dry.

When the new relay shows up I'll put everything back and see if the problem persists. If so, my guess is its something with the alarm ecu or one of the alarm components. Hopefully it's just the relay.

The good news is that after 6 months of dealing with this she's running better than ever for the past four days!



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[LA1995classi]

Thanks for the encouragement revoR. It's nice to see another Classic owner in the deep south. I've had my 95 for about nine months now and have yet to see another roaming the streets of New Orleans. I haven't taken her off road yet but plan to hit the Bonnet Carre spillway sometime soon.

Next time you're headed south let me know!

 

[LA1995classi]

Here's an update. Replaced the alarm relay with a new relay from AB. Everything is great. No whine from the radio. No lockout. Everything is great except now the alarm and central locking does not work! Lol. Maybe the alarm ecu is shot.

I disconnected the battery to reset everything but the key fob does not engage the alarm. Locking the door with the key locks the door but does not engage the alarm. I'll probably live with it like this. Central locking and an alarm is not really important to me anyway.




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[LA1995classi]

The fob works (worked). I was waiting to post an update but the problem has returned. Since the alarm ecu is out of the loop I figure the mfu is the next suspect. I've ordered a new (used) mfu and hope to install it this weekend.

Unfortunately one of my brake lines decided to puncture itself today while I was changing my transmission and transfer case fluid. Tomorrow I'm towing to the shop to get new brake lines. I hope to have it back in time to spend next weekend replacing the mfu. It looks tight under the steering wheel. Any advise on the multi function unit replacement job would be appreciated.




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[LA1995classi]

Here's an update for anyone experiencing the same symptoms. I replaced the MFU (multi function unit) and for two weeks the truck runs perfectly (knock on wood)! I also set the base idle which was set way too high and cleaned the intake plenum and IACV port with Amsoil power foam. I'm now idling strongly and perfectly at 650 RPM.

After installing the new (used) MFU, fuse 8 in the under dash fuse box blew and my dash lights and right side parking lights went out. After blowing 5 new fuses I snipped the wire to the dimmer rheostat and that kept the parking lights on and the fuse from blowing. I need to hunt down the short between the fuse box and rheostat but I drive during the daytime and the truck is running so good I'm afraid to mess with anything right now.