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Heat control question

Heat control question

Old October 16th, 2018, 06:06 AM
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Heat control question

So one of my Delta's weird quirks is the heat control is stuck on cold. The lever just wont move over to the heat position. Its stuck and wont move more than a 1/2" to the right. I'm not entirely sure where to start looking on this. I'm trying to track down a repair manual for it. Now that its getting colder out I'd love to not freeze my buns off. LOL Any insight would be awesome. I don't want to start ripping apart the dash if the controls go somewhere else. Thanks!

Its a 1970 Delta 88 Custom 350 Rocket
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Old October 16th, 2018, 06:17 AM
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The heat door is most likely controlled by a cable. They do get stuck. Look under the dash and start with the heat/cold slider and trace the cable. Check to make sure the damper door moves freely. You will need to remove the cable off to do this. Unfortunately if the car has AC you may need to remove some ductwork 1st to see anything.
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Old October 16th, 2018, 06:20 AM
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Originally Posted by Oldsmaniac View Post
The heat door is most likely controlled by a cable. They do get stuck. Look under the dash and start with the heat/cold slider and trace the cable. Check to make sure the damper door moves freely. You will need to remove the cable off to do this. Unfortunately if the car has AC you may need to remove some ductwork 1st to see anything.

Thanks so much! I def. will do that this weekend and let you know how it goes.
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Old October 16th, 2018, 06:42 AM
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I just went through this with my 67 Delta, which uses the same HVAC box as your 70. The temperature control door is cable operated and the cable does corrode and gets stuck. In my case, the heater core had leaked on the cable, causing it to rust. Do not force the cable, as that's how I broke mine. You will need to remove the cable and hang it vertically to allow you to slowly drip penetrating oil down the cable and into the sheath. As the oil works it's way down, you should be able to start moving the cable. No one makes replacements for these. I have an old KD tool for twisting the loops onto the ends of the music wire cable, so I was able to fabricate a new cable to go inside my old sheath.

To disconnect the cable, you will need to remove the ducting that bolts to the HVAC box under the dash, which will give you access to the lower end of the cable at the temp door. Once you remove that end of the cable, actuate the door lever by hand to verify that it isn't the door that's stuck. The other end of the cable is buried in the HVAC control head. I was able to access the screws that hold the head to the dash through the radio opening.

If you do need to replace the music wire cable, these are photos of the tool that forms the loops.






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Old October 16th, 2018, 07:09 AM
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Joe you are amazing! Thank you so much for the info! I'm def going to do this this weekend! Now, I just gotta figure out what fuel sending unit it takes and I'm done fixing her issues! lol



Originally Posted by joe_padavano View Post
I just went through this with my 67 Delta, which uses the same HVAC box as your 70. The temperature control door is cable operated and the cable does corrode and gets stuck. In my case, the heater core had leaked on the cable, causing it to rust. Do not force the cable, as that's how I broke mine. You will need to remove the cable and hang it vertically to allow you to slowly drip penetrating oil down the cable and into the sheath. As the oil works it's way down, you should be able to start moving the cable. No one makes replacements for these. I have an old KD tool for twisting the loops onto the ends of the music wire cable, so I was able to fabricate a new cable to go inside my old sheath.

To disconnect the cable, you will need to remove the ducting that bolts to the HVAC box under the dash, which will give you access to the lower end of the cable at the temp door. Once you remove that end of the cable, actuate the door lever by hand to verify that it isn't the door that's stuck. The other end of the cable is buried in the HVAC control head. I was able to access the screws that hold the head to the dash through the radio opening.

If you do need to replace the music wire cable, these are photos of the tool that forms the loops.






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Old October 16th, 2018, 08:22 AM
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Originally Posted by deaditedelta View Post
I just gotta figure out what fuel sending unit it takes and I'm done fixing her issues! lol
Fuel gauge sending units are not made for this car. Why do you think you need a new one? What does the gauge do when the ignition is on? There are some troubleshooting steps that could lead to a solution short of having to get to the sending unit, which requires removing the gas tank and is no picnic. Often all that is needed is a cleaning of electrical contacts.
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Old October 17th, 2018, 09:25 AM
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Originally Posted by jaunty75 View Post
Fuel gauge sending units are not made for this car. .
Ohhh boy, the gauge usually hangs around 1/4 of a tank. once in a while it sails up to over full then back down and stays at 1/4. Bloody thing is possessed. Owner said it was stuck but I've had the car since July and its acted funny since I got it. I filled the tank and left it for a week hoping maybe it was just stuck but nope. She flies up to over Full then goes haha just kidding and back to the original position of just about 1/4
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Old October 17th, 2018, 10:08 AM
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Originally Posted by deaditedelta View Post
once in a while it sails up to over full then back down and stays at 1/4.

She flies up to over Full then goes haha just kidding and back to the original position of just about 1/4
This is why it's important to know exactly how the gauge is misbehaving before attempting a fix. A gauge that moves past F is an indication of an open circuit as the sending unit is just a variable resistor with Full corresponding to 90 Ohms of resistance and Empty corresponding to zero Ohms. An open circuit creates infinite resistance, so that's why the gauge pointer not only goes to F but well past it. Your gauge jumping around like it does could be a sign of nothing more than a loose ground connection.

Attempting any wiring diagnosis and fix requires potentially crawling around under the car. You need to find where the ground wire from the sending unit attaches to the car's body or frame and make sure that connection is clean and tight. The connection is not protected from the environment, so after nearly 50 years, it's easy for there to be an accumulation of crud and corrosion around the connection point.

If confirming the ground is ok doesn't fix the problem, then you need to find where the wire coming from the dash gauge connects to the wire coming from the sending unit. These wires and their connection point are usually around the rear license plate area, possibly in the trunk or more likely behind the license plate. You need to separate this connector, connect the side coming from the gauge to Ground, and turn the ignition key ON. The gauge should immediately go to E and stay there. Then disconnect the wire from ground. The gauge should immediately go past F and stay there. If it does these two things, then the gauge on the dashboard and the wiring between it and the rear of the car are OK. You would then need to turn your attention to the sending unit itself, which would mean removing the gas tank in order to get at it. Since identical replacements are not made for these cars, your options are to repair or have repaired the unit currently in the car or replace it with something similar that IS still made.

I had this issue with my '67 Delta 88, for which new sending units are also not made. I found that the sending unit for a '72 Buick LeSabre, which I think also fits other GM full-size cars of the early '70s, drops right in and is an adequate replacement. I don't know if this would be true for your car, but this is the kind of thing you would have to pursue if your sending unit is beyond hope. You could also, of course, try to find another full-size '70 Oldsmobile in a junkyard and take the sending unit from that, assuming it still works or could be repaired, but locating one might not be simple.



Here's a diagram out of the 1970 Olds Chassis Service manual showing the sending unit in your car. (The Delta 88 is a "B" body.) It is the canister type, where the float is a hockey-puck-looking thing that rides up and down on a shaft inside the canister. This is exactly the type of sending unit that was on my '67 Delta. The float can easily get stuck inside the canister, which was the problem I had. I tried cleaning mine and getting it good and loose, but I could never get it to work reliably, so I went to a new unit.





Here's the actual sending unit as pulled out of my car and disassembled.








Here's what it looks like assembled. There should be a filter sock attached to the bottom, but that had decayed and broken away on my unit.






Here's what a complete unit, WITH filter sock attached, looks like. I found this photo on ebay. Yes, these sending units are sometimes found on ebay, but they cost an arm and a leg if they're NOS parts, and I wouldn't buy a used unit pulled from another car unless the seller was asking $1.95 for it.






Here's the exact unit I purchased for my car. It's Spectra Premium part number FG106A, and it's $50.79 plus shipping at Rockauto. I'm sure you can get one at your local auto parts store, too, as Spectra is probably the only manufacturer of new sending units for these cars, and they sell through many vendors.

It wires up exactly the same as the sending unit currently in your car.

Yes, it has two pipes, one for the fuel and one as a vapor return line. The unit on my car had only one pipe, so I just capped the smaller one. From the service manual diagram, it looks like your unit will have two pipes, too, so this should be a even easier replacement than it was for my car.





You can certainly live without a functioning gas gauge, but it gets to be a pain to be writing down the mileage each time you fill the tank and remebering to fill up again before you go more than 200 miles or something like that. Unless you're lucky enough to find that the problem is just a loose connection somewhere, it will likely be a pain the neck to get the gauge properly working again, but it would be worth it if you plan to keep and drive the car.
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Old October 17th, 2018, 10:52 AM
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Jaunty, you are amazing!! Thank you so much for the info. I can't wait to dig in this weekend and start checking out these little issues. Heat comes first though lol. It's getting cold lol!! But thank you all so much for this info!! It's exactly what I needed to get going on my new girl! You guys are fantastic!!
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Old October 17th, 2018, 11:07 AM
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Originally Posted by deaditedelta View Post
Jaunty, you are amazing!!
Thank you. Counting my wife, this makes two people who now think so!
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Old October 17th, 2018, 11:20 AM
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By the way, if you're going to be working on this car to any significant degree, you want a copy of the '70 Olds Chassis Service Manual. These are on ebay all the time. Here's one for sale right now, but there are many others. Make sure to get an original, paper copy, not a pdf version on CD.

https://www.ebay.com/itm/1970-Oldsmo....c100642.m3226





And while you're at it, get the 1970 Fisher Body manual as it covers many things, such as windows, doors, exterior trim, etc. that are not covered in the chassis manual.

https://www.ebay.com/itm/1970-Fisher-Body-Service-Manual-Chevrolet-Pontiac-Oldsmobile-Buick-Cadillac/372424664192?hash=item56b63d6480:g:blcAAOSwvWtbjU~-:rk:18f:0&vxp=mtr


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Old October 18th, 2018, 05:29 AM
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Funny the car came with the fisher body manual, I definitely will get the chassis book too!! Thank you!
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