I've got this puzzling electrical problem. While driving down the interstate at 65mph+ sometimes the voltage will drop to around 10 volts ( guestimated on the stock gauge ), at the same time the tach will quit working. When the voltage suddenly kicks back up, the tach starts working again. Also, if OD is switched off when this happens I can't switch it on until the voltage goes up! This has been happening for a month or more and I'd like to fix it before it takes the permanent drop. I'd hate to give them Ford boys the opportunity to snicker at a Dodge doing a Ford imitation on the shoulder of the interstate! Any help would be greatly appreciated.<br>bigredbrick

 

I sounds to me like your computer is going out. It controls voltage regualtion, overdrive, speedo, cruise, intake heater, and a few others. I would pull the plug on the firewall and clean it real good and make sure it has a good connection. Also check the plug on the computer itself. Hopefully it is not that, but it does sound like it. If it is the computer, AutoZone of all places can get them for about $180. The ******* wants right at $800. I had to replace mine last year in my truck. Bill

 

Had a similar problem with an 88 with a gas engine.<br>Truck would intermittently discharge, blow voltage regulators, eat modules like candy.<br>Replaced underhood harness with a JC whitney replacement.<br>Problem solved. <br>Check all underhood grounds, weatherproof connectors for corrosion, all it takes is one to go bad and the pcm does not get the signals it should. <br>Just a suggestion.<br><br>Rich

 

Bill, thanks for the reply even tho it's not what I want to hear! Any diagnostic check to be sure? $180 is alot for a &quot;spare&quot; part. I always wind up with spares when I start replacing to fix a problem- sometimes I get it right!<br>Rich, I'll try checking the connections more carefully this time, tho I don't really want to break the sealed harness connection at the firewall. I guess I need to yank the battery and pull the computer to check its connections?<br>Do you know what a &quot;check engine light&quot; code 5-5 means?<br>Thanks, Chris

 

code 55 means &quot;end of codes&quot;.<br>If you don't have anything before that, then no codes have been set.<br>I think you also loose any stored codes if you disconnect the battery, so you'd have to re-create the fault for a new code to be set.<br><br>Bob.

 

This sounds exactly like the problem that brought me to this board after 4 months chasing the problem. I'll tell you what fixed mine. Check your crank sensor. On mine it was a broken ground wire at the round 3 pin plug. On the front of the head the CSS wire passes through a bracket with lots of clearence. Mr. Gravity in tandem with Mr. Vibration will let the connector pull the wire against the bracket and wear through it. When it happens you will get an intermittant ground problem. This is why it comes and goes. BTW if required, I have a good computer for a 92 or 93 with auto trans which I purchased only to not solve my problem. Hope this helps Rick

 

Hi Bob, thanks for the info. I was hoping for a clue to the problem, oh well.<br>Rick, did your lights dim when you were having the problem? I forgot to mention that one. Also, my cruise control doesn't work, that is if I'm doing it right- I'll check the owners manual. Tomorrow I'll check out the crank sensor wires along with other things.<br>Thanks, Chris

 

Lights will dim when volts drop. here's what quit working; volts to 10, cruise, od, speedo, a/c. My post describing this was in June 2002. Took it to ******* who diagnosed bad alt. New alt, new batt, new speed sensor, new AutoShutdownDown relay, new Control Module (computer) and problem still persisted. Then we found a broken wire to the CSS. Repaired wire and all is well. Mine would work once in a while, which made it even more frustrating. And there were NO CODES for no crank signal. Frustrating and expensive until I got help here.

 

Check temp sensor &amp; wire also to make sure preheater is not kicking on. Severe voltage drops from this along with a weak batt or alt will make it drop drastically. Loss of ground can make temp goto 0 causing excitement for the intake heater and loss of excitement for the alternator. Good luck!<br> -RATCHET-

 

Rick, checked the CSS wire at that clamp, showed some abrasion but not worn thru. Checked the connecter at the ECM and it looked good. In fact, all electrical connections I've checked have been clean, tight and no corrosion. I bought the truck from the original owner in Reno, NV- very dry climate! Just checked the AC and it works.<br>Most of the time I have normal voltage. In 50 miles sometimes it drops 2 or 3 times and sometimes it doesn't drop for a couple days. <br>Ratchet, which is the temp. sensor? I'm wondering if there's a way to wire a test light to the preheater to let me know if it is kicking on while driving? I don't have a manual with wiring diagrams, but maybe I can figure it out. <br>Thanks, Chris

 

I recently had a simular problem on my 92 with varing voltages anywhere from 10 volts to 14 volts. I chased this problem for awhile. 2 things that were bad was the negitive battery cable was not clean, fixed it. Next I cleaned under the wire that is attached to the body and ran two additional 10ga grounds to the body directly off the battery, one to the post ender the dash and one to the bed of the truck.<br><br>Still had occasional varying voltages and come to find out I had a pinched wire for some camper lights that I had installed a couple years back. I recently tore all the wiring out for aux transmission fan, campr lights and some other items and replaced with SJO cable and installed new relays and switches.<br><br>Also, when the voltages went low my dash gauges would go crazy and not read anywhere near right. After replacing wiring and running additional grounds all seems to be good now.<br><br>I also thought that the ECM and or alternator was going until I did the above.<br><br>Good luck.<br><br>Jim

 

I finally got tired of the problem and got a ECM thru Kragen. Autozone had a much better price but their supplier doesn't have any. <br>Well, I installed it and still have the problem! :'( I guess if I'm going to diagnose the problem by throwing money at it the next thing to buy is a new crank sensor- probably what I should have bought first. :-[<br>To recap the symptoms; voltage drop to around 10 volts, simultaneously the tach quits reading, the problem is intermittant and totally random, at 65mph it rarely affects OD and cruise control, at 45 or so OD is on and off depending on voltage.<br>Any suggestions? Chris

 

I would still bet on the crank sensor going bad. It might start acting up once it gets hot which means it has an internal fault. Basically its a magnetic core with a coil around it and it sends a pulse every time the crank pully notch goes by. If the coil has a break in it, you might get a good signal for a while until it heats up.<br><br>J-eh

 

Lil Dog, <br>Do you know how much one goes for? Can I get one from a parts store or from dealer or Cummins? Also, what's the spec for the gap?<br>Thanks, Chris

 

Lil Dog and Greatwhite were right! Bought a new crank sensor thru the dealer for under $100, installed it and all has been right for 250 miles. The new sensor had some improvements to reduce stress on the wires at the pickup.<br><br>Thanks for the help, eh<br>Chris