A few misc questions, defrost vent, speedo led's, wiring, computers

[hrc200x]

The project: '75 4x4 frame w/dual tanks, '83 cab, '84 incab wiring harness (fuse block out to doors cargo light, etc), '88 clip from blazer (quad stacked headlights) '86 suburban heater and a/c wiring harness and fiberglass shrouding on firewall.

The questions: Why is there a large gap where the "Y" shaped defroster vent hooks up to the large box that the heater core mounts in? I've looked on 4 other 80s chevys and all the same way.

Sunday I took the wiring out of the '84 donor truck. On the back of the speedo there was a plastic thing with 2 or 3 wires going to it that was bolted with a very small bolt, had like a 5 or 5.5mm head on it, went in close to the speedo cable? What is this?

There is a light green and dark green wire that exit the cab close to the distributor I seem to remember these being for dual tanks. Will that wiring be compatable with a '75 selector valve?

The '83 cab had a spot to mount a computer up under the glove compartment, the '84 truck and '86 burb did not. Did they quit them in '83 or move them to another location?

[87 STEPPER]

Answer to question #2 that is the VSS= Vehicle speed sensor it's for the computer to use for the cruise control.

[hrc200x]

Interesting, what is it monitoring in the speedo gauge?

[87 STEPPER]

If you look in the hole that it was mounted in you will see what looks like a propeller and it acts as a reluctor to open/close every time a blade break the beam and uses that info to calculate speed.

[Captkaos]

Y question: Can you get a pic of what you are talking about?
Speedo question, VSS, it is used for cruise control
Selector, Isn't the 75 mechanical, I can't remember....

Depending on the emissions level, it should have a place for the ESC on the early models and ECM on the later.

[hrc200x]

I can have a pic of the Y defroster duct maybe this weekend, but I'll try to explain better. The large Y shaped air duct that blows on the window... follow the down to where it attaches to the main air duct with all the vaccum lines going to it, it should attach with one bolt in sort of a egged out hole. Where the Y defroster duct meets the main air duct there is probably a inch gap on the firewall side and 1/4 to 1/2 inch gap on the cab side. Even if you could get a tight fit on the cab side, the firewall side seems like it would still have a gap since its mounts at an angle. The 4 screws on the top of the dash that hold the passenger and drive side defroster in kinda determine the angle of where it has to go on the bottom side.

By mechanical do you mean I have to manually flip a lever or somthing? If so, no its all electrical, but I'm guessing none of the plug ins are the same.

[Captkaos]

None of the plugs on a 75 will be the same as an 80's version. It can be made to fit/work though. I have a buddy that used the wiring and cab from an 86 and integrated his 75 harness to it and it has dual tanks from his 75 frame.

[hrc200x]

Here is a picture of the gap, as you can see towards the firewall inch or so gap, opposite side fairly tight. Tried two different defroster Y pieces and both the same.

Is the little bracket to run the vaccume and hot/cold cable through?

[hrc200x]

Does anyone know if the spade clips on the outside firewall where it plugs into the back of the fuse block are removable? Seems like you should be able to stick a thin wire next to the clip to release it and the clip should just pull out? There is too much of the black sticky stuff around the clips to really tell.

If you can find out exactly how he got his dual tanks to work that'd be great. sounds very similar to mine only with '84 in cab wiring. Still trying to decide to use '75 engine bay wiring or '84. I almost have to use '84 because of the 3 plug ins that go to the wiper motor.

What are some good web sites for parts to order such things as braided brake lines, brand new steering box, complete cab weather stripping?


I just keep thinking of more questions... Did somthing with the master cyclinder or the lines running up to it change from the 70s to 80s? I'm attempting to keep the '75 lines and use a '85 or so master cyclinder (plastic fluid resivour), the lines to bolt up, but they need to be reversed, just wondering if that will cause problems?

Also, how do I edit the main thread title so it changes on the "1973 - 1987 Chevrolet & GMC Pickups Message Board" main page?

[Captkaos]

That defrost hookup doesn't look right, did the truck some that way?

Are you talking about repinning the fuse panel junction tabs, yes that is how you do it. this is how he got his working. Just used a Haynes manual and some help...

[hrc200x]

I looked on 4 80s chevys all with AC at home here and all are the same, I didn't notice if there was a gap or no gap when I took it out of the burb.

Yea, I was talking about re pinning the fuse block, but for a different reason... while taking the engine bay wiring out of the donor '84 truck, chevy had a pink wire running way under the truck, I didn't want to crawl under it at the time being in deep grass with bugs, spiders and ticks around, so wanted to just unpin it rather than cut it. Ended up pulling the truck out to gravel and unplugging it, I think its the fuel gauge sender wire.

How about this question: What are some good web sites for parts to order such things as braided brake lines, brand new steering box, complete cab weather stripping?