Newbie - attempting to repair Ford circuit board

[Apophasis]

Hello,

I’m seeking any advice on repairing a Ford Anti Slosh Module for a 1995 Mustang. The circuit board seems to be intact, but one or more capacitors seem dead. Im brand new to the hobby. I have a Hakko fr-300 desoldering gun, a Hakko fx-951 soldering station, 60/40 w/rosin flux .6mm solder, and a flux pen (low solids no residue).

This will be my first soldering attempt so I plan on practicing a few times on a blank board before I give it a go. The information on the internet is overwhelming and difficult to sift through so I don’t know if there is anything I am missing. My questions are:

• Are there specific capacitors better suited for high heat vehicle applications (that sit inside a dashboard in the sun)?
• Can I upgrade the type of capacitor rather than just replace what Ford installed. (Better temperature range, better material, etc)
• is it better to just replace all the components now rather than later (it is difficult to get to the circuit board once placed)?
• do I have to use the same style of capacitor, or do I merely need it to have the same specs?
• is there any function test I can conduct on the circuit to see if it works prior to installing it back in the vehicle?
• how do I test the varister?

Further Info: I measured the capacitance of all my capacitors and recieve between 106 and 107 (from memory, I believe it was uF). However, two of the capacitors measured “OL”. The only distinguishing marks I can see list 104. Once I desolder them, I will be able to see the print slightly better than I can now.

 

[Robert_fay]

There are automotive grade caps. Often you will see them noted with an AEC-Q200 certification or noted for automotive applications.

I would not change the composition of the cap, however you are generally ok to raise the temp and the voltage. I generally recommend this when someone has issues with caps in a tv. Generally speaking the automotive lines are overbuilt and would not need to be bumped in temp or voltage.

 

[kellys_eye]

I presume you measured the capacitors 'in-situ'? In which case the measurement readings may well be affected by external wiring/components.

What actual fault symptoms do you see?

 

[Apophasis]

I presume you measured the capacitors 'in-situ'? In which case the measurement readings may well be affected by external wiring/components.

What actual fault symptoms do you see?

Hi,

Thank you for the response! I am not sure what ‘in-situ’ means. But the capacitors were still attached to the PCB and they are disconnected from all power sources. I used a fluke 87-v to obtain the measurement by placing the leads on both sides of the capacitor.

The actual problem is that my vehicle’s fuel gauge is unresponsive. My mechanic said it was the anti slosh module. He attempted to locate a new one, but they are hard to find for my make and year.

I looked for a circuit diagram for the module, but again can not locate for my make and year. So I am left with an attempt to repair and a budding hobby in soldering.

Because of the modules usual location behind the vehicles dashboard and connected to other circuits (no wires), it is difficult to diagnose it while in use.

 

[Apophasis]

There are automotive grade caps. Often you will see them noted with an AEC-Q200 certification or noted for automotive applications.

I would not change the composition of the cap, however you are generally ok to raise the temp and the voltage. I generally recommend this when someone has issues with caps in a tv. Generally speaking the automotive lines are overbuilt and would not need to be bumped in temp or voltage.

Thank you!

 

[kellys_eye]

Yes, in-situ meaning 'still mounted on the board'. For a definitive test you need to remove one of the component wires.

Capacitors (non-electrolytic anyway) tend to be very reliable - automotive class even more so. You can test the electrolytic (big blue one), the diode, resistors and varistor using you meter. If they all measure within specification then the obvious suspect has to be the IC which itself is an in-house device and potentially impossible to source a spare.

But what about the fuel gauge itself? Sure it's not gone open circuit? Or the sender?

Do you have a wiring diagram for the fuel measuring system? Please post it if you do.

 

[Apophasis]

I’m not sure about the open circuit. The vehicle is still with the mechanic. I can say his diagnosis seams to be backed up by several similar accounts on various Mustang forums. Because the slosh module seems to be the easiest to diagnose and possibly fix, I decided to start there. There are other simple issues (the fuel sender, wiring to the console, etc), but this is a pretty good mechanic and according to his statement, he has already gone through the standard procedures to locate the issue.

Sorry, I haven’t been able to locate a diagram. Other info, all the rest of the gauges on the console are currently working correctly. Only the fuel gauge is broken.

So the tldr version is: I haven’t checked, but I hope I can reasonably assume the slosh module is the issue.

 

[davenn]

I have a Hakko fr-300 desoldering gun, a Hakko fx-951 soldering station, 60/40 w/rosin flux .6mm solder, and a flux pen (low solids no residue).

if you have rosin flux cored solder, there is absolutely no need for extra external rosin flux !

Further Info: I measured the capacitance of all my capacitors and recieve between 106 and 107 (from memory, I believe it was uF). However, two of the capacitors measured “OL”. The only distinguishing marks I can see list 104.

But the capacitors were still attached to the PCB and they are disconnected from all power sources. I used a fluke 87-v to obtain the measurement by placing the leads on both sides of the capacitor

As @kellys_eye said, you cannot measure caps in circuit and expect a correct reading .... isn't going to happen

There are automotive grade caps. Often you will see them noted with an AEC-Q200 certification or noted for automotive applications.

that does not appear to be the case here .... all look standard caps

do I have to use the same style of capacitor, or do I merely need it to have the same specs?

preferably the same style ...... none of them are oddball types

Capacitors (non-electrolytic anyway) tend to be very reliable - automotive class even more so. You can test the electrolytic (big blue one), the diode, resistors and varistor using you meter. If they all measure within specification then the obvious suspect has to be the IC which itself is an in-house device and potentially impossible to source a spare.

completely agree with this statement



Dave

 

[dave9]

You appear to be in the US. Slosh modules are not hard to find in the US. By just doing a google search for "Ford Slosh Module" I get the first row of hits as 4 of them for sale, one with a different pinout but the other 3 look right for your application, but with one difference, that your board has a varistor where they have a transistor. Those are only the first two hits Google showed, there are probably more choices on eBay.

https://www.ebay.com/i/253375368040?chn=ps&dispItem=1
https://www.ebay.com/i/282876274757?chn=ps&dispItem=1

There are also videos for how to bypass this board. It essentially just measure the fuel sender float resistance value and uses some analog logic to average it and/or filter out extreme values like you'd seen when accelerating, decelerating, cornering.

I saw a schematic of this but only the placement in the fuel circuit and a poor automotive-grade schematic at that, nothing about the circuit itself though looking at the boards you can see that it's a quad opamp on some.

The capacitor choice isn't so critical. I mean obviously it should be rated higher than 14.4V typical alternator level but next typical cap rating is 16V, get what will fit. 100uF, I would guess this is a pseudo-timing capacitor and the capacitance value averages the fuel level voltage. If so then if you went half that at 47uF, or higher like 220uF, it wouldn't be a big deal. Your choices of capacitor are probably limited most by wanting one with axial leads as there could be clearance issues trying to adapt something else that's radial leaded or surface mount, but it does not need to be an electrolytic capacitor otherwise.

As far as trusting your mechanic's diagnosis, "Maybe". I trust details and facts more than comprehensive assumptions, especially when it comes to mechanics and electronic circuits. Did he measure the correct resistance from the fuel sender? On this slosh module, two pins are power and ground for the opamp and one is input from the sender and the other, output to the gauge. By merely jumpering the input to the gauge output, he should have observed the gauge working again if it is this module that has failed.

 

[Bluejets]

Maybe worth a try giving that contact plate and the mating socket in the vehicle a good clean and squirt with crc.

 

[Apophasis]

You appear to be in the US. Slosh modules are not hard to find in the US. By just doing a google search for "Ford Slosh Module" I get the first row of hits as 4 of them for sale, one with a different pinout but the other 3 look right for your application, but with one difference, that your board has a varistor where they have a transistor. Those are only the first two hits Google showed, there are probably more choices on eBay.

https://www.ebay.com/i/253375368040?chn=ps&dispItem=1
https://www.ebay.com/i/282876274757?chn=ps&dispItem=1

There are also videos for how to bypass this board. It essentially just measure the fuel sender float resistance value and uses some analog logic to average it and/or filter out extreme values like you'd seen when accelerating, decelerating, cornering.

I saw a schematic of this but only the placement in the fuel circuit and a poor automotive-grade schematic at that, nothing about the circuit itself though looking at the boards you can see that it's a quad opamp on some.

The capacitor choice isn't so critical. I mean obviously it should be rated higher than 14.4V typical alternator level but next typical cap rating is 16V, get what will fit. 100uF, I would guess this is a pseudo-timing capacitor and the capacitance value averages the fuel level voltage. If so then if you went half that at 47uF, or higher like 220uF, it wouldn't be a big deal. Your choices of capacitor are probably limited most by wanting one with axial leads as there could be clearance issues trying to adapt something else that's radial leaded or surface mount, but it does not need to be an electrolytic capacitor otherwise.

As far as trusting your mechanic's diagnosis, "Maybe". I trust details and facts more than comprehensive assumptions, especially when it comes to mechanics and electronic circuits. Did he measure the correct resistance from the fuel sender? On this slosh module, two pins are power and ground for the opamp and one is input from the sender and the other, output to the gauge. By merely jumpering the input to the gauge output, he should have observed the gauge working again if it is this module that has failed.

Thank you!

I actually purchased a similar module on eBay (same year, and driveline), but did not have any success. It appears the 94-95 module is unique when compared with the others. Which seems to be the case for other components I have had to replace. I found my exact slosh module on eBay, but so far they are out of stock.

My back up plan is to use the bypass method, but I wanted to give a shot at repair first. This project is less about the most effective way of getting the car running and more about an opportunity to Play around with circuit boards. I’ve been watching various UTube videos about proper soldering and circuit repair.

So, while I do want to give a good attempt at the repair, I won’t be hurt if it fails.

I really appreciate the info on the capacitors. That’s the stuff I’m trying to figure out. How the circuit appplies to voltages in regards to the vehicle, if there is one type better than the next, etc.

I totally agree with your assessment of trusting the mechanic. He is pretty good, but regardless, I have to trust his word until I get the car back.


Again, thanks a bunch to everyone helping out. I am sure it seems like basic stuff, but everyone’s advice gives me jumping off points and proper terminolgy to continue looking into this stuff!

 

[Apophasis]

Copy that. After the photo I tried cleaning it with a new toothbrush and 91% rubbing alcohol.

 

[Apophasis]

if you have rosin flux cored solder, there is absolutely no need for extra external rosin flux !






As @kellys_eye said, you cannot measure caps in circuit and expect a correct reading .... isn't going to happen



that does not appear to be the case here .... all look standard caps



preferably the same style ...... none of them are oddball types




completely agree with this statement



Dave

Quick follow up? I get that the numbers won’t be accurate. But will I be able to tell if one is broken or not? So, in other words, although the values are off, the fact I do have values for all but two capacitors shows those two are possibly broken?

 

[dave9]

Whip out the soldering iron, desolder one leg of each capacitor in question, then you have it out of circuit and can measure it. Hemostats or a thin/micro needle nose pliers can make this easier to pull the lead out, but even a toothpick can work. The 100uF large electrolytic cap is really the only one you should need to do this to. The others are probably fine if they don't look cracked and their solder joints are good.

If there is any corrosion on the electrical contacts, either on the module OR on the gauge cluster connector, then you may need a more abrasive cleaner. I usually use brasso metal polish in such occasions, wipe it away and flush with electrical contact cleaner, but not on thin gold plating (don't need to, gold does not corrode). The petroleum solvent in brasso also helps to dissolve random gooey sludge, but the old formulation of brasso (came in a metal can not plastic) worked much better at goo removal.

If the contacts on the gauges are coated conductive carbon on traces, like you might find on mylar plastic, rather than a mechanical metal contact, don't use brasso or any other polish. In that case a dry paper towel should suffice, is more abrasive than a wet one but not overly so like metal polish.

 

[davenn]

I get that the numbers won’t be accurate. But will I be able to tell if one is broken or not? So, in other words, although the values are off, the fact I do have values for all but two capacitors shows those two are possibly broken?

in circuit, no you wont be able to tell

the only cap that may have failed on there is the big blue electrolytic one at the bottom, they can dry out and loose capacitance
often with no external visible signs

the other 4 caps on there, the 3 at the top and the one between the connector and the IC will not partly fail and since they
look in perfect condition, it is 99.999999999% likely that they are OK as they would fail catastrophically .... ie. a burnt charred mess


Again, so there is absolutely no confusion
It is pretty much IMPOSSIBLE to reliably test capacitors in circuit

a good capacitor will measure open circuit, a faulty capacitor will likely measure low resistance or short circuit. The problem is, that when in circuit, you don't know if that short or low resistance is coming from the possibly faulty cap or is the effect of other components around it

This is why @kellys_eye said you have to unsolder and lift one end of the cap you are testing, so that the rest of the circuit wont affect your readings

 

[Apophasis]

in circuit, no you wont be able to tell

the only cap that may have failed on there is the big blue electrolytic one at the bottom, they can dry out and loose capacitance
often with no external visible signs

the other 4 caps on there, the 3 at the top and the one between the connector and the IC will not partly fail and since they
look in perfect condition, it is 99.999999999% likely that they are OK as they would fail catastrophically .... ie. a burnt charred mess


Again, so there is absolutely no confusion
It is pretty much IMPOSSIBLE to reliably test capacitors in circuit

a good capacitor will measure open circuit, a faulty capacitor will likely measure low resistance or short circuit. The problem is, that when in circuit, you don't know if that short or low resistance is coming from the possibly faulty cap or is the effect of other components around it

This is why @kellys_eye said you have to unsolder and lift one end of the cap you are testing, so that the rest of the circuit wont affect your readings

Awesome. I will try that. Thanks again folks!

 

[Budice69]

The anti slosh benefits do not warrant fixing board. Jumper the 2 contacts on one side of board, put insulation over other 3 contacts (electrical tape works fine). Reinsert in instrument backplane. Now sensor feeds direct to gauge. Works fine on my 1991 tbird LX, 3.8 naturally aspirated.

 

[dave9]

^ Welcome to the forum. After 3 years, I expect that this has been sorted out already, though it is good to have more info about your workaround.

 

[narkeleptk]

^ Welcome to the forum. After 3 years, I expect that this has been sorted out already.....

You'd be surprised... I once didn't notice the date was about 2 years old on a thread at another forum and replied with some help, Turns out he hadn't fixed it yet and still needed the help. He was finally able to get it sorted out with a donor eeprom file I sent him for the module.

Its a good answer for those searching Anti Slosh terms in google. Probably how the poster found the thread.