1998 Caravan erratic RPM

[ddecastro]

Hi friends, i have an strange problem with my van: in idle mode, when i turn on any electric device that use a hight current (power window, lights, AC, operating wheel) the rpm goes down (sometimes 100 to 200 rmp less than the normal idle level), the ECU correct the peak problem and increase again the rpm to idle level...it's annoying, but i survive to this.

But, sometimes, when i keep my AC turned on, and the event occurr, cause i've use the power window, for example, the rpm goes down to a point that the ECU doesn't react, and the van power off...

I know that the voltage regulator is inside the ECU, so change the ECU for this issue is too much for me....more considering that i'am in Argentina, and a new ECU cost here 1000 U$S.....and i don't know if changing the ECU will solve the issue...

Any ideas ? Anyone experience a similar problem ?

Thanks in advance
Diego

PD: Sorry for my english..

[mbrahmer]

Sounds like too much load on the alternator. Check to make sure the battery is fully charged, then test the system voltage when this happens. I suspect you will find the voltage dropping well below the 13.8v the system likes. Possibly the alternator/regulator.

[mikefaster]

Almost sounds like something is kinda crossing Postive and Ground...

I recall having a problem like that, but isolated to ONE item... One time I had a bad window switch, or a bad rear defroster switch, both of which had crossed grounds, and caused the lights in the car to dim as well as the engine speed to drop... The circut breaker would trip almost immediately after and then come back on and it would do it again if I hit the switch... A fused item would most likely just blow the fuse... Usually the Dodges have a fusible link or a Giant fuse under the hood in the relay/fuse box...

It DOES sound like it's more internal in your case; I gather it could be the computer or alternator...

I would try this... Try a different alternator if that's possible and see if there is any change... Or better yet, disconnect the wires from the back of the alternator, tape them if necessary, and then see if it does the problem with your electrical components... Your battery must be fully charged, of course... You would be running without the alternator charging... If the problem STILL occurs, then it probably is NOT the alternator or computer...

That way, you can perhaps islolate the problem...

Computers (and a good used alternator) are pretty cheap on EBAY and most people will ship out of the country if you ask them to...

There is nothing wrong with having a few extra parts lying around... It's different nowadays... 15 years ago, you weren't a good mechanic if you just "changed parts"... Nowadays, things are cheap enough where your time is what's valuable... If I know a problem is either "A" or "B", sometimes it's worth buying them both in order to save time and get the vehicle back on the road quicker...

Good luck...

[ddecastro]

Originally Posted by mbrahmer

Sounds like too much load on the alternator. Check to make sure the battery is fully charged, then test the system voltage when this happens. I suspect you will find the voltage dropping well below the 13.8v the system likes. Possibly the alternator/regulator.

Hi, thanks for your answer, next weekend i will check the voltage level to see if it drops below de value you indicate.

Thanks
Diego

[ddecastro]

Originally Posted by mikefaster

Almost sounds like something is kinda crossing Postive and Ground...

I recall having a problem like that, but isolated to ONE item... One time I had a bad window switch, or a bad rear defroster switch, both of which had crossed grounds, and caused the lights in the car to dim as well as the engine speed to drop... The circut breaker would trip almost immediately after and then come back on and it would do it again if I hit the switch... A fused item would most likely just blow the fuse... Usually the Dodges have a fusible link or a Giant fuse under the hood in the relay/fuse box...

It DOES sound like it's more internal in your case; I gather it could be the computer or alternator...

I would try this... Try a different alternator if that's possible and see if there is any change... Or better yet, disconnect the wires from the back of the alternator, tape them if necessary, and then see if it does the problem with your electrical components... Your battery must be fully charged, of course... You would be running without the alternator charging... If the problem STILL occurs, then it probably is NOT the alternator or computer...

That way, you can perhaps islolate the problem...

Computers (and a good used alternator) are pretty cheap on EBAY and most people will ship out of the country if you ask them to...

There is nothing wrong with having a few extra parts lying around... It's different nowadays... 15 years ago, you weren't a good mechanic if you just "changed parts"... Nowadays, things are cheap enough where your time is what's valuable... If I know a problem is either "A" or "B", sometimes it's worth buying them both in order to save time and get the vehicle back on the road quicker...

Good luck...

Thank you mikefaster for the time you took to answer my question, i've received (last weekend) a new ECU (i have another problems that required the change), and, cause inside the ECU is the voltage regulator, this will be my first test. If this do not fix the 'electric' issue i will try to unplug the alternator to check if the problem persist, and i will let you know how it was..

Thanks again
Diego