help identifying wire near wiper switch

[hpg4815]

This one was a hard one to search the forums, so I am posting to see if anyone can help. I have a new dash wire harness from H&M and coming off the same group of wires going to the wiper switch connector I see this wire with the clip on it. It has power when touched by the light tester so it is live. I do not not think it goes to the A/c controller, but I did find this tab on top off the headlight switch, but not sure that would be for a wire with power.

Thanks

 

[Nacho-RT74]

It should be long enough to reach the HVAC control. A/C and HEATER harness are not part of the main harness. That’s the wire to feed the control switch to feed the blower either A/C or HEATER car. It should be inserted into the corresponding switch plug.

It should be hot just with key in ACC or RUN.

 

[devinism]

That tab, or terminal on the headlight switch is for a ground.

 

[hpg4815]

Ok. Thanks

 

[hpg4815]

Ok. Thanks

It strange as the old wire harness has the plug to the a/c controller but the new H&M one does not. Lastly I hooked up a ground wire to the light switch and my wiper switch started working so this is great news for me.

 

[72RoadrunnerGTX]

The extra ground tab on the headlight switch indicates a later aftermarket repo switch, originals didn’t have it. Appears you are installing a Dakota Digital RTX cluster. The wiper switch needs to be grounded to work correctly, adding that ground wire and wipers start working indicates the DD cluster frame was not grounded sufficiently. Original grounding for both switches would have been through the mounting and a dash harness wire connection at the voltage limiter for the original Rallye cluster.

 

[Nacho-RT74]

It strange as the old wire harness has the plug to the a/c controller but the new H&M one does not. Lastly I hooked up a ground wire to the light switch and my wiper switch started working so this is great news for me.

The original A/C harness is linked to the underdash harness just at that wire to the A/C control plug, to the feed for accesories (to feed the clutch source) and from 71 to 73 with terminals to bulkhead to feed the clutch and blower (on 74 these get a grommet running throught the firewall out of the bulkhead), but still with those attached to the underdash harness is an independent one from the underdash harness itself.

When car is Heater (non A/C), the underdash harness remain the same but the Heater harness is linked just at bulkhead for blower and that same black wire to power up the system.

That’s the reason why A/C and Heater harnesses are not really part of underdash harness (same for both setups) as one piece, but just linked at certain points. This configuration allows to manufacture/sell/install same underdash harness for both kind of setups. Not just by actual manufacturers but also factory was like that.

So, you need to reuse your A/C harness, removing the terminals from locations mentioned and reinstalling the same ones on the new underdash harness. Still if being a NOS harness

 

[Sixpactogo]

You mentioned the extra wire was near your wiper switch connector. I remember E body wiring harnesses had an extra wire that was un-used for a 2 speed wiper but was needed for the 3 speed wiper. Could that be what it is?

 

[72RoadrunnerGTX]

Pretty sure it’s been identified as C1-14BK* (14 ga black with a white tracer), heater or A/C power lead. There is indeed an extra wire run needed to convert the dash harness to support a 2sp wiper to 3sp swap. Switch to bulkhead.

 

[Nacho-RT74]

No extra wire to make the two to three speeds wipers conversion. Underdash harness is the same for both… plug is the same with the diff existent between 71 and 72/74 (same wires diff prongs disposition).

The only parts needed to upgrade or downgrade between 2 and 3/var speeds are the switch, motor and harness (3 speeds motor comes with harness attached anyway)… and of course the main link and crank.

This is for B bodies, and pretty sure E body is the same.

On a side note, 3 speeds and variable are same motor, the diff is the switch itself. Variable feature is 70/71 B/E body feature only (B just 71)

Several considerations about the year for the conversion of course, specially about the linkage.

Talking from experience. I fit a Variable setup on my original 2 speeds 74. Later motor with the taller cap, but still using a 71 var speeds switch. Found the correct 71 plugs for the switch but wires are the same than the 72/74. Just plug changed.

 

[72RoadrunnerGTX]

No extra wire to make the two to three speeds wipers conversion. Underdash harness is the same for both… plug is the same with the diff existent between 71 and 72/74 (same wires diff prongs disposition).

The only parts needed to upgrade or downgrade between 2 and 3/var speeds are the switch, motor and harness (3 speeds motor comes with harness attached anyway)… and of course the main link and crank.

This is for B bodies, and pretty sure E body is the same.

On a side note, 3 speeds and variable are same motor, the diff is the switch itself. Variable feature is 70/71 B/E body feature only (B just 71)

Several considerations about the year for the conversion of course, specially about the linkage.

Talking from experience. I fit a Variable setup on my original 2 speeds 74. Later motor with the taller cap, but still using a 71 var speeds switch. Found the correct 71 plugs for the switch but wires are the same than the 72/74. Just plug changed.

Strange, I distinctly remember having to add a switch to bulkhead wire run for a 2sp to 3sp conversion on something many years ago. Now that you mention it, haven’t run into it anytime recently with this platform, diagrams do support the dash harness wiring is the same for both systems.

 

[Sixpactogo]

No extra wire to make the two to three speeds wipers conversion. Underdash harness is the same for both… plug is the same with the diff existent between 71 and 72/74 (same wires diff prongs disposition).

The only parts needed to upgrade or downgrade between 2 and 3/var speeds are the switch, motor and harness (3 speeds motor comes with harness attached anyway)… and of course the main link and crank.

This is for B bodies, and pretty sure E body is the same.

On a side note, 3 speeds and variable are same motor, the diff is the switch itself. Variable feature is 70/71 B/E body feature only (B just 71)

Several considerations about the year for the conversion of course, specially about the linkage.

Talking from experience. I fit a Variable setup on my original 2 speeds 74. Later motor with the taller cap, but still using a 71 var speeds switch. Found the correct 71 plugs for the switch but wires are the same than the 72/74. Just plug changed.

As I mentioned in post #8, E body cars had an extra wire for 3 speed wipers. That was me talking from experience.

 

[hpg4815]

The extra ground tab on the headlight switch indicates a later aftermarket repo switch, originals didn’t have it. Appears you are installing a Dakota Digital RTX cluster. The wiper switch needs to be grounded to work correctly, adding that ground wire and wipers start working indicates the DD cluster frame was not grounded sufficiently. Original grounding for both switches would have been through the mounting and a dash harness wire connection at the voltage limiter for the original Rallye cluster.
View attachment 1773448

Yes correct on all fronts. I got a new headlight switch and did noticed that grounding tab was not on the old one, and while I was installing the DD cluster the wipers were coming on as I bumped the wiper switch into metal during install but did not come on once mounted. I painted the dash so there might too much paint to get a ground, but since the headlight switch and the wiper switch are attached to the same metal part of the DD cluster it is grounding once I added that ground wire to the headlight switch. I ran it to the same spot where the dash harness ground is attached.


How are you liking your DD? you have factory A/C?

 

[hpg4815]

The original A/C harness is linked to the underdash harness just at that wire to the A/C control plug, to the feed for accesories (to feed the clutch source) and from 71 to 73 with terminals to bulkhead to feed the clutch and blower (on 74 these get a grommet running throught the firewall out of the bulkhead), but still with those attached to the underdash harness is an independent one from the underdash harness itself.

When car is Heater (non A/C), the underdash harness remain the same but the Heater harness is linked just at bulkhead for blower and that same black wire to power up the system.

That’s the reason why A/C and Heater harnesses are not really part of underdash harness (same for both setups) as one piece, but just linked at certain points. This configuration allows to manufacture/sell/install same underdash harness for both kind of setups. Not just by actual manufacturers but also factory was like that.

So, you need to reuse your A/C harness, removing the terminals from locations mentioned and reinstalling the same ones on the new underdash harness. Still if being a NOS harness

let me look at my old dash harness, there was no clear spot to disconnect the A/C plug (harness) from the rest of the dash harness, but I could have missed it.

 

[72RoadrunnerGTX]

 

[72RoadrunnerGTX]

How are you liking your DD? you have factory A/C?

Posted about my RTX install a while back here. Yes, has A/C. Haven't had a chance to drive it a bunch yet, so far liking it pretty well.

 

[hpg4815]

View attachment 1774232
View attachment 1774234

I see. Ok thanks.

 

[Nacho-RT74]

View attachment 1774232
View attachment 1774234

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THIS.

This black wire comes from fuse box and is the power to feed blower

Plus the Acc feed to the corresponding rubber mold also coming from fuse box, which will feed the clutch function.

Plus the two wires to the bulkhead for blower and compressor clutch. On 71 both running to the NSS block, on 72 and 73 the blower to the NSS block and the Clutch to the engine harness block.

Those are the wires which links the A/C harness to the underdash harness

 

[Nacho-RT74]

As I mentioned in post #8, E body cars had an extra wire for 3 speed wipers. That was me talking from experience.

Interesting. Althought I can’t see a reason for that since motors are the same and switches are virtually also the same as far I recall. And wiring to bulkhead is also the same, running into the same 4 ways plug. Engine bay harness side is also the same.

A bodies are also the same. In fact talking on A bodies the only difference is between foot pump washers or electric washers. This are the only physical difference on switches where electric washers wiper switch are press in shaft and foot pump are fixed shaft. Sooooo if you install a electric washer system on a foot pump car, you need to add the wire running between switch and bulkhead (and of course on engine bay side aside the change the reservoir)… on A bodies at least. Even this, plug to switch remains the same, just one cavity left empty on foot pump cars.

Also up to 74 on A bodies, two speeds wipers are foot pump, while 3 speeds are electric pump washer. Then from 75 all are electric. Maybe similar to E bodies hence why the wire difference you found? Was that extra wire for 3 speeds a brown one?

You can even install a B body switch onto a A Body or backwards and wiring and plugs (if same year) will be the same. But the physical size/lenght of the switch will allow or not this posibility. Thinking the same about the E bodies.

 

[Nacho-RT74]

Sorry the highjack, but I think this is interesting