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Being intermittent, start checking wiring/connections for open or shorted wiring. Start doing the wiggle tests as well. When you take apart and clean up connectors, repack them with dielectric grease.
 

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If nothing shows up on a wiggle test, then I would suspect something in the alternator is intermittant. It is possible to upgrade to the 120 amp unit, but keep in mind that the higher amp alternator is slightly bigger and heavier. It might be tight fitting it in on a 3.0. There is really no need to upgrade unless you have added some large current drawing accessories like a monster amp or a 12 volt to 120 VAC inverter. I put a larger alternator on my minivan 3.0 because it was the cheaper option. It is a tight squeeze and PITA getting it installed compared to the original 90 amp unit.

As an FYI, my alternator failed in the same way (after several minutes of high load), restoring itself completely on re-starts. The only difference was, I had a lot of mileage on mine, so it was more likely to fail.
 

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Discussion Starter #23
John. I am in the same boat. The 120 amp alternator out of napa is 139 dollars new. I really dont run anything like that . I am only planning on wiring in a set of fog lights as the headlights on this car suck big time. I think I can get away with the 90amp that is in the car
I am planning on taking it off the car and bringing it with me to the NAPA by work and hope they can order the right one. I think that 24 years has taken its toll on it. I plan on doing the wiggle test and see if that helps any. I was just very surprised that it worked fine then all of a sudden dropped like a stone
 

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Discussion Starter #24
preformed the wiggle test tonight in the cold as soon as the alternator quit. Nothing changed. Volts were down to 11.7 as I was doing this. Guess it is time to change it out. I will let everyone know
 

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Discussion Starter #25
ok here is an update on this issue. So I got a 12o amp denso type alternator specific from this car. The alternator tested good at the store. I put it in finally last night since it was warm enough to do it. Right after I get everything connected and what not I start the car.
Got a check engine light and 11.9 volts on the battery. Ok this does not make sense.

so I follow the service manual and it states to ground k20 (second terminal on the field) and the alternator starts putting out voltage. I did this only for a few seconds as my multi meter climbed beyond 15v.

I know the new alternator works now so that is not the problem. I checked the main battery wire for continutity and that is fine. I also checked the ground and that is fine. If I put the multmeter probe on the positive batt post .. and the negative on the alternator I get a really good ground.

The only thing I have not checked (it was late) was the k20 to the computer terminal.

This morning I start the car and while it was a little rough running the alternator was putting out 14.5 volts. I am pulling my hair out tring to figure this out.

I am thinking about putting a external voltage regulator in and bypassing the computer. My only question is how do I turn off the check engine light?
 

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Sounds to me like the internal voltage regulator in the PCM is bad as it is monitored by temp also for charging purposes. Do you have the fresh air hose from the PCM to the air cleaner still there? That helps to cool down the PCM boards as air is drawn over them also.
 

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Discussion Starter #27
floridaman I have everything stock on the air inlet. So if the internal regulator is bad is there any way to by pass and keep the check engine light off?
 

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If it is determined the computer is the issue a new computer would be fairly inexpensive. I've seen people bypass the voltage regulator only to have the computer fail in another way soon after.
 

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I would disconnect the battery, disconnect the PCM, and really, really probe every single contact in each half of the connector system. Especially pay attention to the wire(s) related to charging. Poke and probe that contact in the harness, put an ohmmeter lead in the female contact and the other lead on K20, and have someone flex the connector quite a bit at each end of the harness. Any interruption in continuity, anything more than a fraction of an ohm reading, or open circuit, and that's where the trouble will be.
 
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Discussion Starter #30
I tested the K20 circut and got continuity at both ends of the computer socket. I did notice that the plastic on the back of the computer connector seemed to be off a little. I clicked that back into place and cleaned all the contacts. Reconnected the computer.

I also charged up the battery to 12.4 volts (it was reading 12.3.) and started the car.

I ran the car for 30 min and there were no check engine lights or power drops. It looks like everything is up to par again . I hope it was just a problem connection at the computer
 

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Discussion Starter #31
I spoke too soon. I drove the car yesterday and about 20 min into my drive around town the check engine light came back on .. and it stopped charging again . ARRRGGGGHHH.. I guess the PCM is bad... I wonder why they went to the voltage regulator in the computer.

Well I guess I am going to have to replace the computer or hook up an external voltage regulator
 

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I spoke too soon. I drove the car yesterday and about 20 min into my drive around town the check engine light came back on .. and it stopped charging again . ARRRGGGGHHH.. I guess the PCM is bad... I wonder why they went to the voltage regulator in the computer.

Well I guess I am going to have to replace the computer or hook up an external voltage regulator
The PCM provides much better control of the charging than an external regulator. You may be fine with an external regulator but the computer does the job better.
 

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I'm still betting on a damaged harness.
 

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Discussion Starter #34
I am just leary that I am going to have the same problem again down the road with a refurbed computer. You cant get a new one now a days
 

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I am just leary that I am going to have the same problem again down the road with a refurbed computer. You cant get a new one now a days
It is so rare they fail I would have no problems with a used junkyard computer in an older car like this. And like Bob says the problem is often not the computer.
 

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These are the female contacts that were used in the harness to the PCM back in the K-car days. These are Molex KK series contacts. They work by curling up under spring tension when mated, and they only make contact with one side of the square male or the round male pins (whichever used) in the PCMs. They also are subject to stress cracking corrosion, and they often fracture with the pieces still in place in the harness, causing these intermittent problems. Terrible design. We avoid them like the plague at work now.
KK contact.JPG
 

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Discussion Starter #37
I know it is rare but knowing my luck I will get two bad ones in a row. What has got be baffled is when I checked the continuity on that k20 circut everything was fine. I wiggled the connector several times with the probe in the connector and it was ok. I am tempted to rewire just find out what the issue might be.

is there any replacement for those connectors?
 

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You could buy new ones at Digikey. But I'd recommend a different contact. If I can find out the dimensions of the pins used in the PCM, I can recommend a good replacement contact that grips the pin on either 2 or 4 sides, and isn't likely to fracture.
 

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Discussion Starter #39
yes I would like to know that myself. If you can let me know a good connector that would be wonderful.
 
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