Weird Wiring/Electrical Problem

[spike42291]

I have a 1988 5.0 gt convertible and ever since i got it a few years ago there has been some weird electric problems. First the tach is really messed up. 90% of the time it just sits around 4k no matter what the real RPM's are and randomly it will decide to work for a few seconds then go back to sitting at 4k. Something else that i believe is related to this is that my headlights will randomly turn off sometimes but go back to normal a few seconds later, (keep in mind that the tach and headlight problem happens even when im just idling in park). Also my left turn signal will sometimes blink normal, or decide to blink every 5 seconds. It's not solely the actual light, but the indicator on the guage cluster as well. The right one is always fine. My left headlight and foglight are dimmer than my right and when i turn my foglights on the left headlight dims even more. I have a feeling that these problems are all related to some section of wiring or plug but im not sure. Any help will be appreaciated.

This ad is not displayed to registered or logged-in members. Register your free account today and become a member on Mustang Forums!

[jrwireman1960]

first thing I would check is the grounds,what you describe could be caused by poor grounds.

[spike42291]

I took out my tach and me and a friend tested it with the meter which showed something was wrong. I got a new chip board for the tach and put it in, and it worked!!

So that problem is taken care of. But that still doesnt explain the headlight and blinker problem.

[hiboostwoody]

The following is a Technical Service Bulletin put out by Ford. I have copied it from my Alldata Pro account. If this doesn't sound like your problem, it could be a poorly grounded or faulty dimmer/turn signal multi function switch.

^ HEADLAMPS-FLASH WHEN FOG LAMPS ARE ON

^ WIRING-HEADLAMP CIRCUIT-INADEQUATE GAUGE WIRE AND TERMINALS
Article No. 89-17-11FORD: 1983-89 ESCORT 1983-87 EXP 1987-89 MUSTANG


LINCOLN-MERCURY: 1983-87 LYNX

ISSUE: The headlamps may flicker on and off when the fog lamps are used for an extended period. This may be caused by overheating of the headlamp circuit # 15.

ACTION: Install new wiring, terminals, headlamp and dimmer switches. Refer to the following procedure for service details. Refer to the following application charts for correct parts usage.

1. Remove the headlamp switch. Refer to the appropriate Car Shop Manual, Section 32-02 for service details.
2. Inspect the switch and connector terminals of circuit # 15 for any heat damage such as discolored terminals or distorted connectors.

3. Perform normal diagnostic procedure if no heat damage is found.

4. Proceed as follows if heat damage is found:

a. Remove the terminals and wire (Circuit # 15, red/yellow) from both the headlamp and dimmer switch connectors.

b. Cut the wire as near as possible to the wire harness tape wrap and throw it away.

CAUTION: IF THE CONNECTORS ARE DISTORTED AROUND THE TERMINAL AREA, THEY MUST ALSO BE REPLACED.

c. Crimp new terminals to the correct length of 12 gauge wire and install them in the connectors.

d. Overlay the new wire along the existing wire harness and tape wrap it.

e. Install new headlamp and dimmer/ multifunction switches. Refer to the appropriate Car Shop Manual, Section 32-42 for Mustang and Section 32-40 for Escort/Lynx/EXP for dimmer switch removal and installation details.

5. Check the system for proper operation.




1987-1989 MUSTANG GT

[spike42291]

Found a bad ground for the lights and blinkers. Everything is all good now. Thanks guys.