1970 - help with engine wiring

[Steve G.]

I have a 1970 BB with ac. I was looking to replace the engine wiring harness. I had assumed the engine harness was separate from the front light wiring harness, but see that mine is connected, or at least taped, together to the front light harness on the driver's side inner fender just below the horn relay. Anyone know if that is correct and how I would proceed to remove the engine harness?

Another wiring question - on firewall, just to left (driver's) side of the TCS relay, there is another electrical device. It is separated from the TCS by only an inch or so. I don't know what it is, but it has two thick wires attached to two separate terminals. One wire is red - it goes over to the horn relay mentioned above. The other is orange with black stripe. It looks like it goes into firewall to passenger compartment. Any idea what this is and are either of these wires supposed to be part of the engine harness? thanks, Steve

[Terry M.]

Re: 1970 - help with engine wiring

Another wiring question - on firewall, just to left (driver's) side of the TCS relay, there is another electrical device. It is separated from the TCS by only an inch or so. I don't know what it is, but it has two thick wires attached to two separate terminals. One wire is red - it goes over to the horn relay mentioned above. The other is orange with black stripe. It looks like it goes into firewall to passenger compartment. Any idea what this is and are either of these wires supposed to be part of the engine harness? thanks, Steve

You got power windows?

Edit: Let me rephrase that -- Does the car have power windows?

[Steve G.]

Re: 1970 - help with engine wiring

Yes, the car has power windows. Is that a power window relay? Windows go up and down very slowly and 'weak'.

[Chuck S.]

Re: 1970 - help with engine wiring

I have a 1970 BB with ac. I was looking to replace the engine wiring harness. I had assumed the engine harness was separate from the front light wiring harness, but see that mine is connected, or at least taped, together to the front light harness on the driver's side inner fender just below the horn relay. Anyone know if that is correct and how I would proceed to remove the engine harness?...

I don't have access to my AIM, but my recollection is that the forward harness, engine harness, and AC harness are all separate and unique harnesses.

In fact, as I remember it, the forward harness leaves the bulkhead panel and goes directly forward along the left hand side of the engine compartment, and the engine harness and the AC harness go toward the right side of the engine compartment along the top of the firewall.

What you are seeing as harness taping may actually be an electrical type tape GM used to bundle the harnesses together. If you examine the electrical section in the AIM, you will see that it calls out the location of these electrical tape bundling ties. This tape differs from harness tape in that it has adhesive...harness tape has no adhesive, consisting solely of plain black vinyl. If the tape has adhesive, it is either a "Bubberized" hack job, or the harness bundling tape.

[Terry M.]

Re: 1970 - help with engine wiring

I believe the object you asked about is a power window circuit breaker. Most say LITELFUSSE on them.

There are a lot of reasons PW can operate slowly. Probably the first is old thick grease in the PW mechanism. Solution there is to take the mechanism apart and clean out the old grease and install new. The step-by-step instructions are in your copy of the Chevrolet Chassis Service Manual. Those instructions will also contain some cautions which could save your fingers and/or hands. Please get a copy, read, and follow it.

The second reason for slow operation is lose, or corroded, electrical connections. The AIM (Assembly Instruction Manual) for your year Corvette will show you where most of the electrical connections are. Disassemble and clean them for good connections.

If you are handy with an electrical meter some simple voltage tests at the door and at the battery will tell you if the motors are getting full voltage. This may help separate the mechanical from the electrical areas.

[Jim T.]

Re: 1970 - help with engine wiring

Steve if you clean up your 70's window tracks like Terry says you should be very pleased with the new performance. I cleaned up my 70's window tracks which also has power windows in 1990, they still go up and down real fast.

[Steve G.]

Re: 1970 - help with engine wiring

Thanks much. Regarding power window literature... my copy of the assembly manual is missing A31 - power window section. I got my AIM with the car. I'll pick up another copy. I have the 1970 Chevrolet Service Manual - but realized it was for the 1969 Corvette after I got it. I do see section on wiring in it. If it is the same as for 1970, I see the power window harness does go from inside the car to a fuse on firewall. Mine has a red wire that goes from the fuse to the horn relay. I can't tell from the picture located on 'Corvette Body 18-21', figure 30 if wire is going to the horn relay or not. In any case, I will try cleaning the mechanical pieces to see if it helps. I'll try cleaning the glass run channels and the regulator. Any advice as to how to remove the GM plastic sheild without destroying it or the caulking?

Regarding the front wire harness - yes, mine has been messed with by one of the previous owners. I am contemplating buying all new harnesses as a result.

[Terry M.]

Re: 1970 - help with engine wiring

The 1969 Chassis Service Manual, with a May 1970 Chevrolet Service News Supplement, is all there is for 1970 Corvette. The Power window -- side glass removal section of the 1969 Service manual should be what you need. I am not sure you need or want to remove the side glass to do this. Maybe you would start a separate thread on that subject so that those who have gone that route can pick this subject from your wire issues.

As to the AIM -- I'll have to see if there is an A31 section. The originals of these things were not always complete.

[Chuck S.]

Re: 1970 - help with engine wiring

...I'll try cleaning the glass run channels and the regulator. Any advice as to how to remove the GM plastic sheild without destroying it or the caulking?

Regarding the front wire harness - yes, mine has been messed with by one of the previous owners. I am contemplating buying all new harnesses as a result.

Plastic shield?!...Are you talking about the anti-theft cover over the door latch, or something specific to power windows (I don't have them)? If you are referring to the cover over the door latch, it is assembled to the rear of the door frame with two screws. The cover has a foam rubber strip gasket on each contact side; no calking.

Harnesses are very expensive. Others would say replacement is cheap insurance to avoid engine compartment fires, but if you inspect the harness carefully for damage or shorts from self-made electricians, my position would be to defer the expense until you have good reason.

With a little ingenuity, damage from hackers can often be repaired by swapping wire ends to bury a soldered splice inside a freshly rewrapped (and carefully inspected) harness. Harness tape is relatively inexpensive, and repair eliminates any possibility of the wire color and terminal configuration not matching the original, because it IS the original.

[Terry M.]

Re: 1970 - help with engine wiring

Plastic shield?!...Are you talking about the anti-theft cover over the door latch, or something specific to power windows (I don't have them)? If you are referring to the cover over the door latch, it is assembled to the rear of the door frame with two screws. The cover has a foam rubber strip gasket on each contact side; no calking.

I thought he was talking about the plastic water shiueld under the door panel. I forgot to address that.

Cut the caulk that holds it on the door with a sharp blade or putty knife. Don't pull on the plastic sheet too much. 3M strip caulk will work as a replacement.

[Steve G.]

Re: 1970 - help with engine wiring

Wow - thanks for all the help! Please do let me know if you find section A31. If its not there, maybe my book is complete after all. The plastic I was referring to was the plastic sheet under the door panel. I will try to save it. As for harnesses - great point. They are expensive. Someone previously suggested to me to buy from L'ectric Limited. I see the Parts Ladi on Ebay has harnesses that are much less expensive. I called them and they said the less expensive ones are from M&H. Has anyone had any luck with those?

I do like the idea of repairing the original harness if I can. I will need an ac harness as mine is cut. But I may be able to salvage the other harnesses. An engine harness is $200, and a forward lamp harness is $300 at L'Ectric Limited.

Steve

[Roberto L.]

Re: 1970 - help with engine wiring

I believe the object you asked about is a power window circuit breaker. Most say LITELFUSSE on them.

[Terry M.]

[Terry M.]

Re: 1970 - help with engine wiring

Very nice Bob. Where is the vacuum control hose to the wiper door actuator?

[Roberto L.]

Re: 1970 - help with engine wiring

Very nice Bob. Where is the vacuum control hose to the wiper door actuator?

The picture was taken some years ago while cleaning the firewall components. Note the wiper motor is missing as well as some hoses and there is some masking tape for reference labeling.

But the picture happens to be appropiate for this thread.

Saludos