Would you assume my ABS control module is bad?

[John Livingston]

The main relay does NOT show current at 85, with the ignition on. I'll double check.

 

[J_C]

Ok, when pump relay 86 shows 12V, does pump relay 85 also show 12V? It should, and if pump relay pin 85 shows 12V, then ABS Control Module pin 17 should also have 12V.

 

[John Livingston]

Sorry. The main relay shows current in either state at 87, and current at 86, albeit down .5V, say from 12.5 to 12 even. Nothing at 85.

 

[J_C]

The main relay does NOT show current at 85, with the ignition on. I'll double check.

If the main relay does not show 12V at 85 with ignition on, that is a problem. I'd do as described in the prior post, #39

 

[J_C]

Sorry. It shows current in either state at 87, and current at 86, albeit down .5V, say from 12.5 to 12 even.

Okay so are we back to looking at pump relay pin 85? Does it get 12V with ignition on? If it does and ABS Control module does not get 12V on pin 17 then there is potentially a fault between these two points, so I would measure resistance between these two points.

If resistance is low, say under 5 ohms, the connection is good and I would wonder if you have a shorted out ABS Hydraulic Unit coil that is pulling the voltage too low, but if resistance is high, then more likely a wiring or connector contact fault.

 

[John Livingston]

Lots of edits! The pump relay never shows any juice either at 85. Juice at 87 always. Similar juice at 86 and 30, with the ignition on.

 

[John Livingston]

Let me look one more time, but I'm pretty sure neither relay ever shows voltage at 85.

 

[John Livingston]

That is the situation. Nothing at terminal 85, on either relay, regardless of the ignition switch's position. Hope I'm not causing you to pull out your hair in frustration! You patience is hugely appreciated.

 

[John Livingston]

It's getting dark enough that I'll probably stop work on this until the morning. I need to go check my poor boat, which is nearly as old as the Mountaineer, to make sure it has heat, as it may get below freezing tonight. If you know anything about Yanmar diesels' cooling systems, for heaven's sake, don't let me know!

I'll go back over your edited remarks above, and I'll look at the wiring diagrams some more.

 

[J_C]

That is the situation. Nothing at terminal 85, on either relay, regardless of the ignition switch's position. Hope I'm not causing you to pull out your hair in frustration! You patience is hugely appreciated.

Okay, if pump relay pin 85 is not getting power with ignition on, but more importantly main relay 85 is not getting power with ignition on, then do as suggested in post #39

 

[John Livingston]

The fuse at 14 still tests good. I get battery voltage on the right side of the fuse socket, with the ignition on. With it off, I get an open circuit measuring from the left side of the fuse socket to socket 85 on the main relay.

 

[J_C]

Then if the diagrams pictured in this topic are correct, you have a break in the wiring or fouled contact between fuse 14 output and main relay pin 85, which is keeping the ABS control module from switching the main relay on.

In post #11 you stated "I get system voltage at 20, the "ignition feed," but nothing at 17", which tells us that the fuse contact must be good, and the wiring at least to S141 wiring split, wherever that might be which I don't know, so somewhere at S141 down to the contact 85 on the main relay would be where the problem lies.

Edit: Previously this section talked about checking for shorts in the wire to chassis ground, but that probably isn't necessary since the control module is getting power on pin 20 and the fuse hasn't blown. It might still be worth the bother to check that there isn't low resistance between chassis ground and main relay socket contact 85, with the relay removed. If the wire is shorting out, then it should be removed or repaired so that it doesn't, and of course if removed, replaced with new wire.

 

[John Livingston]

I was trying to run 12V to the light-blue/pink wire, which should feed 85. I just tried to get the DMM to show continuity between 85 and where I was poking into the wire, but I'm not sure I ever actually got through the insulation. I usually have good luck with these taps. Maybe I'll try the smallest size. I obviously don't want to break the wire! I do have an inline fuse ready to go, if I get continuity. Before I try again, I'll follow your suggestions above, about checking for a short, etc., and will report back.

 

[John Livingston]

I get an open circuit measuring resistance between 85 and chassis ground. I'll keep trying to get, gingerly, through the insulation on the light-blue/pink wire. If I do get continuity between that point and 85, I'll tap in a fused wire to the + side of the battery, and, if nothing blows, see if there's juice at 17. I think I'll take a nap first, though!

 

[J_C]

If your meter probe or tap tip/needle is too large for your liking, for testing purposes I'd just grab a small sewing needle and poke it in with a pair of pliers. Steel isn't a particularly good conductor but good enough to check continuity to either end of the wire run.

 

[J_C]

While you could do a fused run to the battery, it seems like a more permanent solution would be to just run a wire from main relay socket pin 85 (or the blue/pink wire section that you have pictured, if it has continuity to main relay socket pin 85), over to ABS control module pin 20, then you don't need the additional fuse added because it's already going through fuse 14.

The other 2 options are to run from either socket pin 85 or the wire if continuous, all the way to the interior fuse panel, but access behind it to add the wire, has to be a lot more work than at the control module pin 20, -OR- that light blue and pink wire is almost certainly going to the bulk wire connector near the firewall, so you could tap or solder to the wire there.

If you can solder, I'd be more comfortable soldering in the wire rather than insulation displacement taps. Granted if the tap connection goes bad in the future, you should get the dash warning light on again, so it won't be a case of expecting your ABS braking to work and not having it.

 

[John Livingston]

I actually tried pushing a large safety pin through the wire, before seeing your note. It went all the way through, into a block of wood this time, instead of my thumb. I still get no circuit between the safety pin and 85, darn it. I'm probably done with that for today, but we'll see. The wire to the battery was just meant to be temporary, as I feared there'd be some unintended current drain if the circuit was always hot.

I can solder. I've also got lots of nice, heat shrink, tinned connectors, from the boat, and even a bunch of Weatherpack connectors, so there are lots of options! Not much good, though, if I can't get a connection to 85.

 

[John Livingston]

Is it tough to remove the underside cover of that relay box? I can't imagine that having access to the underside of the socket will really accomplish much, but I'm willing to try anything.

 

[J_C]

I don't have first hand experience dealing with your relay box, but I imagine that access inside the relay box is achievable with the right combo of small tools, though I'd prefer the plastic was warmed up so it isn't as brittle, and that "might' allow pulling the relay socket contact out, or at least the closer you get to the box, if not inside of it, the greater the chance that you're past where the original wire's fault is, or possibly just taking the box loose you might discover rodent damage or something, though at the same time, you are disturbing a bunch of 27 year old wires, so there is that risk of further damage.

 

[John Livingston]

It sure seems like I ought to be able to make contact there, right outside of the housing. I'll work at it some more tomorrow. I may put in two safety pins, a few inches apart, and see if they "talk" to each other. I appreciate the warning about disturbing too much. That's a very good point!