What is your thought?

A while back I posted I think in my build thread about this.
Back ground at O-dark thirty going to work the dash turn signal lights would dimly blink / flash.
At the same time the motor felt link it sputtered and would hear something like a electric zap.

At first I thought it was the ICM as it was leaking it's guts running down the inner fender and onto the garage floor. I replaced it with top of the line NAPA one.
A little while later it did the same thing so it was not the ICM but did  not know what it could be?

Well today again at O-dark thirty going to work the dash turn signal lights started dimly blink / flash again.
Unlike before when I got off the high way, the only place it would happen, it happened on a road I could go slower.

Well I am sure I found what was happening and but know why the lights would blink?
The AC compressor was kicking on and off. This would cause the motor to sputter as it turned on & off, look at how much power it pulls from the motor just to run it.
The same goes for the noise as the compressor makes, the zap noise.
What I cant figure out is why the the dash turn signal lights blink / flash dimly?

Now I think why it stopped for a bit was 2 reasons.
1 it was hotter out, the AC was on full so it did not turn on / off.
2 I think I added a little more charge to the system.

Since then I had a leak and when recharged it did not get a full charge, in the 40's on the low side where it should be mid 50's low side.
Also the OAT was cool but humid so I had the AC on normal but the temp up about half waybecause it was blowing to cold, so the compressor I could see turning on / off.

So why the dash turn lights blinking / flashing dimly?
Dave ----

My first thought is a bad or weak ground.

grumpin wrote

My first thought is a bad or weak ground.

I would think that but I have all the factory grounds in place and they were cleaned of paint before I put them in place when rebuilding the truck.
Battery cable to frame rail then to top starter bolt. there is a 10 ga wire from the block to the fire wall. Think I put the wire from the fire wall to the hood like factory and the new battery cable had a wire off it I ran to the fender just in case. Every thing on the truck electrical wise works as it should from day 1.

Being a flare side and a early model it dose not have a ground wire for the tail lights up to the fire wall like the later ones do so the tail lights ground to the frame and have also worked since day 1, even the back up lights.

The compressor has its own ground I think to the motor, have to look as I dont remember now but the clutch has 2 wires, power & ground.
It has a new clutch as the old one stopped working and the gap is set right as per the book.

I will have to see if turning on & off the AC makes the dash lights dimly blink / flash now that I know 1 of the causes.
Also being I now know I may not rush in to this farther, put off what you can till it breaks

I just thought of something when filling in something above.
All my dash lights have been replaced with LED bulbs, wonder if that plays into this?
No I am not going to swap in normal bulbs to test, to much work and I am lazy
Dave ----

Dave - Have you checked the ground for the things in the cab?  It is G701 and is on the inside of the firewall directly ahead of the radio.  If that isn't good then things in the cab can flicker.

Gary Lewis wrote

Dave - Have you checked the ground for the things in the cab?  It is G701 and is on the inside of the firewall directly ahead of the radio.  If that isn't good then things in the cab can flicker.

Not on the early trucks.
The harness is from 02/81 installed in the body of 11/80 truck and dose not have that firewall ground.
The only lights I can see that dimly blink / flash are the dash TURN lights, nothing else I can see dimly blink / flash. The turn signal & 4 ways still work when this is happening.

Factory grounds in place.
Battery cable to top of frame rail and then on to the top starter bolt.
10 ga wire from engine to firewall, cab / body ground.
Think I put the fire wall to hood wire back.
I think I also ran a wire from the battery cable to the inner fender because it was there on the new cable.
Being a early flare side I dont have the ground wire in the harness to the tail lights and they are grounded to the frame. All electrical works since day 1 even back up lights and inside cab lights.

The other thing is I am running LED bulbs in the dash cluster and wonder if that plays into it?
I would think it would be all dash lights and not ONLY the TURN lights?

The noise is the compressor as it is noisy but with all going on and it short cycling it was hard to pin point it till yesterday. I think the short cycling was because it was cool, fan on low and the temp turned up to half and it could also be a little low on charge?

Now that I know what is happening, AC compressor short cycling, I am not to worried about it at this time.
Thanks for the help
Dave ----

FuzzFace2 wrote

Not on the early trucks.
The harness is from 02/81 installed in the body of 11/80 truck and dose not have that firewall ground.

If you don't have that ground that may be the problem.  I just checked the 1980 EVTM and it shows G701 used pretty much as it is in the later trucks.  But instead of the EVTM saying it is on the firewall ahead of the radio it says it is "In harness attached to "Y" brace."

So you are supposed to have a G701.  And it is supposed to be grounded.

As for when the change was made from it being attached to the "Y" brace vs the firewall, apparently that was during the 1981 production as the '81 EVTM says it is on the firewall.

Gary Lewis wrote

FuzzFace2 wrote

Not on the early trucks.
The harness is from 02/81 installed in the body of 11/80 truck and dose not have that firewall ground.

If you don't have that ground that may be the problem.  I just checked the 1980 EVTM and it shows G701 used pretty much as it is in the later trucks.  But instead of the EVTM saying it is on the firewall ahead of the radio it says it is "In harness attached to "Y" brace."

So you are supposed to have a G701.  And it is supposed to be grounded.

As for when the change was made from it being attached to the "Y" brace vs the firewall, apparently that was during the 1981 production as the '81 EVTM says it is on the firewall.

And we all know the Ford books are 100% right
It has been a wile that I did the dash / harness work but what ever wires went to ground it was put back I just dont remember anything there

Being it is just the dash turn signal lights when the AC compressor cycles I am not too worried ATM.
Thanks
Dave ----