90 MKVII Electrical Trouble

[Pete'sMKVII]

I've got an issue with a 1990 MKVII that's exhibiting some intermittent electrical squirreliness.

I have for some time had occassional periods of lights blinking on the dashboard. The airbag light sometimes blinks - at night with the lights on. Often the abs light comes on as well. This happens, 10 or 15 minutes into a trip and it only happens at night when the headlights are on.

Sometimes while this is happening, the clock light dims out. One night this week, the headlights also dimmed and the car quit running.

After a while on the side of the road, it restarted and got me home.

My mechanic diagnosed a weak alternator based on a measured output of 11.7 volts. He replaced the alternator, but on the way home from picking up the car, I got the tell-tale dashboard flicker and saw my headlights dim some.

So I've still got the problem and want to avoid buying parts that don't fix it.

Is this a common scenario? Sure sounds like a bad ground somewhere, but WHERE?

By the way, I did the dashboard ground wire fix some time back and that worked like a charm.

Thanks for any help you can offer.

Pete.

[Drake_tr7]

First off ground bond from battery to block, and block to chassis. And check to make sure the regulator is grounded good.
(elementary I know but the basics are what bites you in the butt ;))

IMO you're dead right, it's a ground.

[Hizhonor]

First off ground bond from battery to block, and block to chassis. And check to make sure the regulator is grounded good.
(elementary I know but the basics are what bites you in the butt ;))

IMO you're dead right, it's a ground.


If you replaced the alternator, replace the voltage regulator.
(unless it's a 3G upgrade with an internal regulator)

Make sure you DO NOT start the car with the regulator off of the strut tower as that is where it's grounded. Also, I agree with the cleaning of the ground wires. Replace as needed. Our cars have about 14 different grounding points and if one or two are loose or disconnected, havoc, mayhem, hair pulling, cussing up a storm breaks out! :eek: ;)

[Drake_tr7]

I tend to think it's a major common ground because there's so many unrelated systems acting up ;)

The headlight grounds for instance, would explain the lights acting up, but have nothing whatsoever to do with dash lights or charging.

[gadget73]

+1 on cleaning your connections. I'd also pull all the wires at the starter relay and clean them up. The entire electrical system comes together right there.

Might not hurt to pull the VR and clean it's mounting points. If that doesn't have a good connection to the body, it won't work properly though I'd tend to expect the voltage to go high, not low.

[Pete'sMKVII]

Thanks, guys, for the advice. Cleaning the big grounds, replacing the vreg and cleaning its ground seem to have done the trick.

I appreciate you taking the trouble to point me in the right direction.

Pete

[Drake_tr7]

Good deal :D

[Hizhonor]

Thanks, guys, for the advice. Cleaning the big grounds, replacing the vreg and cleaning its ground seem to have done the trick.

I appreciate you taking the trouble to point me in the right direction.

Pete

Cool! That's why we're all here; to share the wealth of knowledge that's here on this site and other Lincoln Mark VII specific sites.

[Funkyking]

So would a bad starter relay cause a total loss of electrical power with a good battery?

'Cause that's what happened to me today on my 86 LSC: One second all is well, then I turned the key and no power at all. I checked the battery and it shows a solid 12.5 volts, but apparently none of those volts are reaching the rest of the car.

[Drake_tr7]

No, a bad solenoid will only deprive the starter itself. When was the ignition switch changed last ?

[2manymarks]

May I remind everyone of the value of one of these inexpensive units that can be plugged into the cigar lighter? It will show battery condition and voltage regulator output. Much of the electrical squirreliness can originate with the charging circuit. Knowledge is power.

[Hizhonor]

May I remind everyone of the value of one of these inexpensive units that can be plugged into the cigar lighter? It will show battery condition and voltage regulator output. Much of the electrical squirreliness can originate with the charging circuit. Knowledge is power.


I have one Uncle Jerry! :p:D:cool:

[Tony T]

So would a bad starter relay cause a total loss of electrical power with a good battery?

'Cause that's what happened to me today on my 86 LSC: One second all is well, then I turned the key and no power at all. I checked the battery and it shows a solid 12.5 volts, but apparently none of those volts are reaching the rest of the car.

This has happened to everybody at some time. Clean the battery posts and cables, bet they are black.

[white lincoln]

What brand of voltage regulator would you guys suggest getting?

[Drake_tr7]

Motorcraft.

[2manymarks]

What brand of voltage regulator would you guys suggest getting?

The last couple VR's I got from the Lincoln dealer were chrome cased and reasonable.

[Funkyking]

This has happened to everybody at some time. Clean the battery posts and cables, bet they are black.


Sure enough! The cables were tight, the negative terminal to ground resistance was effectively zero, but there was over 20 Ohms resistance between the positive terminal and the cable!

Silly person that I am, I assumed that if the cables were tight on the post, there was a good electrical connection.

[Hizhonor]

Motorcraft.


Double ditto dat! Nothing beats replacing a part with the right part that belongs on the car. When it comes to the electrical components of our Mark VIIs, it's worth the extra $$$ to buy Motorcraft parts.