Electrical How many amps could an amp draw draw....

mikeynonos · Oct 20, 2021

Okay...fuse is good. Please tell me, what am I doing wrong here?

Kid wita 5oh · Oct 20, 2021

Meter could be bad. Do you have another to try?

mikeynonos · Oct 20, 2021

Kid wita 5oh said:
Meter could be bad. Do you have another to try?

Unfortunately, no

Mustang5L5 · Oct 20, 2021

Settings are correct, but I'm not understanding that reading. Those meters usually pop the fuse over 10A.

Here’s what I get on my car with nothing on. 0.2amps at rest

mikeynonos · Oct 20, 2021

Mustang5L5 said:
Settings are correct, but I'm not understanding that reading. Those meters usually pop the fuse over 10A.

Here’s what I get on my car with nothing on. 0.2amps at rest

Thank you....that is what I get until I connect the Yellow wire and the Blue wire to the solenoid. I just realized the fuel gauge and oil pressure gauge are not working either.....I have a feeling everything might be connected. I even removed the cluster from my '92 to see if it was the gauges, but they do not work either.

Mustang5L5 · Oct 20, 2021

Yellow wire goes to the ignition switch and to fuse #1 (15a). I assume removing the fuse doesn’t change the load.

I’d start by unplugging the ignition harness with the big yellow wire, and see if that reduces the load at the battery.

These are those two pages out of the EVTM and you can see how the yellow wire is connected

Also, don't rule out the ignition switch itself. These things were known to catch fire.

mikeynonos · Oct 20, 2021

Mustang5L5 said:
Yellow wire goes to the ignition switch and to fuse #1 (15a). I assume removing the fuse doesn’t change the load.

I’d start by unplugging the ignition harness with the big yellow wire, and see if that reduces the load at the battery.

These are those two pages out of the EVTM and you can see how the yellow wire is connected

Also, don't rule out the ignition switch itself. These things were known to catch fire.

Thank you for the pages from the EVTM.

Here is where I am at now. I realized the wiring is different form the 1992 to the 1989, so of course that cluster would not work unless I missed wires around, which I will not do. I found another thread about testing the gauges, sending unit, and went through that as well.

With Key Off, oil pre gauge reads 0 as it should...Key On Ignition Off the oil pressure gauge reads dead center, and if I remove the sending until wire and connect it to ground, the gauge hits max. I tested the wire (w/r) at the cluster and it reads 1.3 ohms, which is right where it should be. It must be the gauge itself, or the sending unit. I have not even tried the fuel gauge yet, as it is not working either.

7991LXnSHO · Oct 20, 2021

As for testing the meter, you can test its amp reading by using a resistance of a known value. I suggest hooking it inline with a 12v bulb to the battery terminals or jumpers. It’s likely that (almost) every car person has an 1157 or 1156 bulb around.
The high or single filament is about 25 watts (depending on brand), it should draw a little over 2 amps when hooked to a 12V source. The wattage for other bulbs you might have can be Googled or found in the Sylvania catalog.
A bulb will also light up when it is connected correctly. So, the evidence it is hooked up correctly is easier than trying to see the electrons with a normal resistor.

If you put the bulb between the battery clamp and the terminal where you have the meter, you can get an idea of if the current leak is at least 2 amps. If it is dimly lit, the current leak is less than two amps.

How many watts is a 1157 bulb?

Bulb Filament Watts High 23.04 1157 Low 8.26 High 26.88 2397 Low 6.72 How many watts does an 1157 bulb draw? Compare with similar items This item 1157...

performancedistro.com

Mustang5L5 · Oct 20, 2021

Here’s the instrument cluster wiring for 1989.

You can isolate the cluster by pulling fuse 18 (15A) and that should eliminate the cluster from the equation

I think your car is an LX, so you can eliminate the low fluid module on page 45. That’s for GTs only

mikeynonos · Oct 20, 2021

Mustang5L5 said:
Here’s the instrument cluster wiring for 1989.

You can isolate the cluster by pulling fuse 18 (15A) and that should eliminate the cluster from the equation

I think your car is an LX, so you can eliminate the low fluid module on page 45. That’s for GTs only

Yes, it is an LX. Swapped with a good oil pressure sending unit, no change.

I also pulled the #18 fuse, cluster went off...still showing same draw at the battery.

Thanks to those of you going through this step by step with me. I've been working on and racing these things since the late 80's and early 90's, but have never ran into this sort of problem.

Here is the problem child....

Mustang5L5 · Oct 20, 2021

Try unplugging the ignition switch next

General karthief · Oct 21, 2021

The alternator plug is another known problem, but I agree on the ignition switch, also is the ground wire from the drivers side head to the firewall connected?

mikeynonos · Oct 21, 2021

General karthief said:
The alternator plug is another known problem, but I agree on the ignition switch, also is the ground wire from the drivers side head to the firewall connected?

Yes, the ground is connected. That was one of the first things I checked as it is a common issue. I have already done the diagnosis on the alternator troubleshooting, and everything there has checked out. Correct resistance and voltage on all wiring. except for one. I did notice that on the green/red wire at the rear of the connector on the D plug had 3.3 volts, rather than the 2.4-2.6, but in the checklist it said anything no voltage, or almost full voltage would be a failed regulator, but it was not less, and not much more.

mikeynonos · Oct 22, 2021

I have not had a chance to dig deeper just yet, as the weather here has not been good and I have no room to move it inside. Hopefully tomorrow I will be able to unplug the Ignition Switch, test the draw, and then move forward from there.

mikeynonos · Oct 23, 2021

Okay, so I went through the recommendations above yet again. Today I went though all of the under-hood grounds again, and then disconnected the ignition switch, the relay for the rear defrost the fuel pump relay, and both fuses #1 and #4. Still was showing a draw. I went back to the starter solenoid, removed all of the wires coming off of it, hooked up the positive cable, and then went through the wires one by one. The Yellow Wire still showed a high draw, and the Blue Wire did as well. I think last time, I had both wires connected when going through the 4-wires splitting off of the Yellow Wire, so I removed the Blue Wire and left Yellow connected. Still, after this, I showed the draw. I started to remove all of the fuses. I looked up and noticed the draw was gone, so I reinstalled them one by one until the draw reappeared. Fuse #8 (Courtesy Lamps; Dimmer Switch; Power Mirrors; Radio; Fuel Filler Door Release). I went through the same process with everything on this circuit. Of course, the last thing I removed was the culprit.....the radio. I have 2 other radios from Mustangs, and both of them, once hooked up, show the draw reappearing. It has all of the factory wiring and plugs, so not sure what would be the cause of this,

Any more suggestions for the radio circuit? The factory amp is hooked up, but the draw only shows once the stereo is plugged in.

Mustang5L5 · Oct 24, 2021

Is this the oem head unit or an aftermarket?

Looks like you may need to seek out another head unit or repair yours.

mikeynonos · Oct 24, 2021

Mustang5L5 said:
Is this the oem head unit or an aftermarket?

Looks like you may need to seek out another head unit or repair yours.

Hi Mike,

It is the factory head unit with factory wiring. I will need to test the wiring coming into the stereo. I have another factory stereo, as well as an aftermarket I had used in my 1992. Once either are plugged in, the show the same draw. Do you think it is possible it is the factory amplifier causing this, or just a bad head unit? I believe I have another factory stereo somewhere, but I will have to dig a little deeper to find it...lol

Rdub6 · Oct 24, 2021

mikeynonos said:
Yes, it is an LX. Swapped with a good oil pressure sending unit, no change.

I also pulled the #18 fuse, cluster went off...still showing same draw at the battery.

Thanks to those of you going through this step by step with me. I've been working on and racing these things since the late 80's and early 90's, but have never ran into this sort of problem.

Here is the problem child....

Nice looking LX!!
Just read through the whole thread..... hope you get it figured out.
Not that I want to see problems, but I enjoy reading these threads, and the advice they provide. No doubt, it will help someone else down the road as well. Good job Stangnet!!

7991LXnSHO · Oct 24, 2021

So, it might actually be an amp amp draw?
I am vindicated!
But seriously, why would several radios do the same thing plugged in if the problem is not there unplugged? Are the harness and individual connectors ok? Has the wiring been messed with?

Mustang5L5 · Oct 24, 2021

mikeynonos said:
Hi Mike,

It is the factory head unit with factory wiring. I will need to test the wiring coming into the stereo. I have another factory stereo, as well as an aftermarket I had used in my 1992. Once either are plugged in, the show the same draw. Do you think it is possible it is the factory amplifier causing this, or just a bad head unit? I believe I have another factory stereo somewhere, but I will have to dig a little deeper to find it...lol

You can bypass the amplifier if you want to try to run the head unit solo.

Reach up behind the radio and find the amp wiring. There is an identical set of plugs that plugs into the amp wiring. Unplug those, and plug the male plugs into the radio. Then test to see if the draw is gone. Radio should work, minus the door speakers

Electrical How many amps could an amp draw draw....

Member

Attachments

I'm definitely not in the original hole

Member

That is…until I whipped out my Bissell

Member

That is…until I whipped out my Bissell

Member

wanna catch the space herp

That is…until I whipped out my Bissell

Member

Attachments

That is…until I whipped out my Bissell

wonder how much it would cost to ship you a pair

Member

Member

Member

That is…until I whipped out my Bissell

Member

So while I wait to figure out my rear end issues

wanna catch the space herp

That is…until I whipped out my Bissell

Similar threads

Privacy & Transparency

Privacy & Transparency