MrEarl

1979 Estate Wagon, AC Blower and Carburetor Problems

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Works fine on Lo and Med but not Hi. Worked for a while after complete AC replacement but stopped. It also didn't work when the "parts swapper garage" replaced the compressor. I know there is a wire running from the compressor to the blower relay and am wondering what association it has with the operation of the blower. I am considering replacing the relay but need to know if there is something else I need to consider.

Just thought about this, maybe I should try it with AC off and heat on......

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No Hi is likely the relay. I’d jumper battery voltage to the blower to see what happens, then check for voltage in/out at the relay. Are any of the other relays the same part number so you can swap for diagnostics?

 

If you lose a lower speed or two, that’s usually a resistor that’s burnt out, but Hi should be straight bus voltage. 

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33 minutes ago, SpecialEducation said:

No Hi is likely the relay. I’d jumper battery voltage to the blower to see what happens, then check for voltage in/out at the relay. Are any of the other relays the same part number so you can swap for diagnostics?

 

If you lose a lower speed or two, that’s usually a resistor that’s burnt out, but Hi should be straight bus voltage. 

 

 Yep, my take as well.

 

  Ben

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 Blower motor high speed is direct 12 volts. If all other speeds are working the resistor is good.  If only high is working then the resistor is bad. Check relay.  Hopefully you do not need to get into the dash again to check the switch itself. 

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Jiggle the fan switch on high.  That's been my experience,  A little to the left worked on my former '78

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On many GM systems, there is a "high blower relay", which helps keep the dash blower switch from cooking over time.  On some middle '70s systems, any time the selector lever was on "inside air", the blower automatically went to "HIGH", with an appropriate switch and wire on the control panel unit to do that.  Unplugging that wire results in all blower speeds on outside air and "RECIR".

 

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6 hours ago, NTX5467 said:

On many GM systems, there is a "high blower relay", which helps keep the dash blower switch from cooking over time.  On some middle '70s systems, any time the selector lever was on "inside air", the blower automatically went to "HIGH", with an appropriate switch and wire on the control panel unit to do that.  Unplugging that wire results in all blower speeds on outside air and "RECIR".

 

 

Thanks NTX...I need to do that on the Electra.  That high speed on recirculate is way too noisy and lack of a lower speed on recirculate is way too much AC for comfort. 

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22 hours ago, avgwarhawk said:

Check relay.  Hopefully you do not need to get into the dash again to check the switch itself. 

 

Already pulled the top of dash off just to make sure I didn't disturb a wire while working on the coolant temp light. First thing I tried was jiggling the switch JD, no sweet spot found. I'm going to verify the part number and go ahead and order a new relay. My main concern  was that it wasn't something associated with the compressor since there is that wire that comes off it and goes to the relay. Thanks guys for all the help, I'll report back how it goes.

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@MrEarlBtw. Did you take temp readings with the infared gun during your trip to Jordan's? Just wondering how it compares to the trial tow readings?

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16 hours ago, JohnD1956 said:

That high speed on recirculate is way too noisy and lack of a lower speed on recirculate is way too much AC for comfort. 

 

This was part of the "Flow Through Ventilation"  system. If the air is in recirculate, then there is no Flow Through Ventilation, so the designer made it only high speed so you would go for fresh air after set temperature was reached when starting the AC on Max in  a hot car. 

 

This is to vent the cabin of unwanted fumes, either from the exhaust (deadly) or fellow passengers eating burritos.... (also deadly😁).  Fresh air good, usually. This was a big improvement over the old car heaters that were recirculate only. And the cowl vent was an improvement over the fresh air intake at the grille in the early 50s that just sucked the exhaust from the car in front of yours in traffic.😨

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2 hours ago, JohnD1956 said:

@MrEarlBtw. Did you take temp readings with the infared gun during your trip to Jordan's? Just wondering how it compares to the trial tow readings?

I did. At midway point which happened to be where the high reading while in tow was made, upon arrival at Jordans and then at arrival bck home. Nothing higher than 195* and that was running at 65-70 in 88* temperate with AC on normal. I'm now taking reading at top of thermostat housing vs at base. 

I still plan on swapping out the radiator, water pump and thermostat. Doing some research on  radiators at the moment

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2 hours ago, Frank DuVal said:

 

This was part of the "Flow Through Ventilation"  system. If the air is in recirculate, then there is no Flow Through Ventilation, so the designer made it only high speed so you would go for fresh air after set temperature was reached when starting the AC on Max in  a hot car. 

 

This is to vent the cabin of unwanted fumes, either from the exhaust (deadly) or fellow passengers eating burritos.... (also deadly😁).  Fresh air good, usually. This was a big improvement over the old car heaters that were recirculate only. And the cowl vent was an improvement over the fresh air intake at the grille in the early 50s that just sucked the exhaust from the car in front of yours in traffic.😨

 

I was under the impression that the recirculate mode was not 100% recirculated air.  It is mostly recirculated air with some fresh air percentage infused.  

 

 

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3 hours ago, MrEarl said:

Nothing higher than 195* and that was running at 65-70 in 88* temperate with AC on normal.

 

Maybe it would be a good thing to isolate the trans from the radiator by running one or two auxiliary  coolers? 

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Posted (edited)

Not sure I'm following you. I have a transmission cooler in front of the radiator and behind the condenser. Are you saying it may be blocking air or transferring tranny heat to the radiator and to possibly move it or?  I have heat sink type transmission cooler that I was planning on adding underneath the radiator shroud but have found the transmission temperatures to be in bounds.

 

https://www.summitracing.com/parts/sum-331000

Edited by MrEarl (see edit history)

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Posted (edited)

Well, if the engine temps were approaching 260 * while towing, but remain @ 195 * for several hours of highway driving without towing, then it seems to me that the towing is causing the trans to heat up and that is, in turn, heating up the engine by using the trans cooler in the radiator.  And in that case, two separate auxiliary trans coolers piped in a tandum pattern in front of the condenser , and eliminating the trans cooler in the radiator as part of the system, should result in not much additional engine temps when towing.  

 

I am just thinking disconnect the trans lines at the radiator and plug the trans cooler ports with bolts.  But I guess I would eventually remove that auxiliary cooler from between the condenser and radiator too.  You have already changed this car for maximum efficiency while towing.  I would not be concerned with originality at this point, but instead reliability. 

 

But that's just my point of view. 

 

And that heat sink looks interesting, but I would think the fore mounted trans coolers would be more efficient, and hardly visible inside that vast cavern between the grill and the condenser.  And some of the reviews of the heat sink are not completely positive on the unit, although that seems to be more about the fit of the fittings.   Hell, I'd even consider putting an electric pusher fan in front of those two prescribed trans coolers for even more airflow if stuck in traffic.

 

I would not be pursuing a replacement radiator for one that held 195*  steady for several hours of highway driving.  

Edited by JohnD1956 (see edit history)
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Me suspects you'll need to get the carb checked for proper power mixture phasing and air/fuel ratio.  How much throttle depression is needed when towing at 65mph on flat roads?  How much on mild hills?  Any trans downshifts?  Does the cruise control maintain speed when towing?

 

Might even need to get the distributor advance specs checked, too!  What manifold vacuum at cruise empty and towing, to see if the vacuum advance still has vacuum in those conditions.

 

Find some speed shop with a chassis dyno and get them to see what the air/fuel mixture at "road load cruise" and "max power".  They might want to sell you some replacement Holley carb, which can be more tunable (easier for them) to replace the OEM QJet.

 

There is a selection of power valve springs for the QJet, to vary when the power mixture on the primary metering rods happens.  Just as there are a whole page full of primary and secondary metering rods, too.  Check to make sure the plastic cam that raises the secondary metering rods has not worn or failed, too.

 

GM's designs typically didn't have good baffles that channel all of the frontal air THROUGH the radiator.  Usually gaps on the sides, by observation.  Also make sure that if there is supposed to be an "air dam" hanging off of the bottom of the core support, to help air get through the radiator, that it's there.

 

IS the lock-up torque converter still hooked up and working?  Just curious.  DO get a trans temp gauge, which can use a magnet to stick onto the bottom of the trans oil pan, just to see what the trans temp is.  270 degrees is the temp above which ATF deterioration usually starts with normal ATF.  Syn ATF is a good bit higher.

 

Just some thoughts,

NTX5467

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Normally I’d recommend to always run transmission fluid through the radiator tank last to maintain consistent fluid temps. They work best in a certain temp range, and running the fluid too cool can be as bad as too hot. 

 

In your neighborhood, that’s probably not that big of an issue, though. Just helped my brother put a cooler on his ‘Burban. He lives in Nebraska and this is his daily, so it’s absolutely a big deal. 

 

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270°F may be where rapid fluid deterioration occurs, but long durations at 225° can be enough to cause significant breakdown. As a general rule, when ATF temps hit 200°F, it’s time to do something different. 

 

Do you still have the electronic carb on this car? 

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6 hours ago, JohnD1956 said:

I was under the impression that the recirculate mode was not 100% recirculated air.  It is mostly recirculated air with some fresh air percentage infused.

 

On my 70 Buick  it is 100% recirculated air. All the evaporator boxes I have repaired on many models of cars the recirculate door seals off the intake of fresh air. I am not aware of any bypass route for fresh air to enter these evaporator boxes.

 

A test would be to disconnect the fuse for the blower, put system in recirculate and see if any air comes through the vents just from driving the car at speed.

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2 hours ago, JohnD1956 said:

Well, if the engine temps were approaching 260 * while towing, but remain @ 195 * for several hours of highway driving without towing, then it seems to me that the towing is causing the trans to heat up and that is, in turn, heating up the engine by using the trans cooler in the radiator.  And in that case, two separate auxiliary trans coolers piped in a tandum pattern in front of the condenser , and eliminating the trans cooler in the radiator as part of the system, should result in not much additional engine temps when towing.  

 

I am just thinking disconnect the trans lines at the radiator and plug the trans cooler ports with bolts.  But I guess I would eventually remove that auxiliary cooler from between the condenser and radiator too.  You have already changed this car for maximum efficiency while towing.  I would not be concerned with originality at this point, but instead reliability. 

 

The heat sink unit was going to be used in addition to the unit between the rad and condenser before I realized I had a engine coolant temp while towing problem. Now considering removing the unit between the rad and condenser and adding a large one in front of the radiator. If I do that I'll definitely just go ahead and swap out the radiator with a 3 core, possibly aluminum.  

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48 minutes ago, NTX5467 said:

Me suspects you'll need to get the carb checked for proper power mixture phasing and air/fuel ratio.  How much throttle depression is needed when towing at 65mph on flat roads?  How much on mild hills?  Any trans downshifts?  Does the cruise control maintain speed when towing?

 

Might even need to get the distributor advance specs checked, too!  What manifold vacuum at cruise empty and towing, to see if the vacuum advance still has vacuum in those conditions.

 

Find some speed shop with a chassis dyno and get them to see what the air/fuel mixture at "road load cruise" and "max power".  They might want to sell you some replacement Holley carb, which can be more tunable (easier for them) to replace the OEM QJet.

 

There is a selection of power valve springs for the QJet, to vary when the power mixture on the primary metering rods happens.  Just as there are a whole page full of primary and secondary metering rods, too.  Check to make sure the plastic cam that raises the secondary metering rods has not worn or failed, too.

 

I had a full tune up with new plugs, wires, set timing etc but am definitely not satisfied with the output of the engine so at SOME point will be looking into all that so wil get back to you on it. Thanks

 

52 minutes ago, NTX5467 said:

M's designs typically didn't have good baffles that channel all of the frontal air THROUGH the radiator.  Usually gaps on the sides, by observation.  Also make sure that if there is supposed to be an "air dam" hanging off of the bottom of the core support, to help air get through the radiator, that it's there.

 

Funny you mention that. I was looking at and measuring the radiator for replacement today and was astonished at all the gaps and space on the sides of the radiator where air could flow right through. Will definitely need attention when new radiator is installed. And yea the air dam is there.

 

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37 minutes ago, SpecialEducation said:

As a general rule, when ATF temps hit 200°F, it’s time to do something different. 

 

 

👍That's my goal for towing.

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What are the conditions when you notice the engine starts to overheat pulling the camper? What is the speed and RPM?  Is it pulling really hard without the transmission downshifting?

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3 hours ago, JohnD1956 said:

You have already changed this car for maximum efficiency while towing.  I would not be concerned with originality at this point, but instead reliability. 

 

Somewhat sadly you're right.   Maybe I'll enter it in Modified next year in Ohio. 😊

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5 minutes ago, Ronnie said:

What are the conditions when you notice the engine starts to overheat pulling the camper? What is the speed and RPM?  Is it pulling really hard without the transmission downshifting?

 

The only time I tested it  was the day I took it to the scales for checking the weight distribution hitch set up. I went through a lot of STEEP Georgia hills and tried to maintain a speed of 60-70 so the engine was really reving most of the time. The tranny performed well, downshifting as should. Tranny temp was below 200 if I recall. That was the same day I had to get back home and get Rita to the ER so am a bit fuzzy in remembering details.

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Posted (edited)
2 hours ago, MrEarl said:

The tranny performed well, downshifting as should.

 

Well that blows my theory of what might be going on.  A friend over the weekend was telling me his Ford truck with a 390 was overheating when pulling his enclosed race car trailer up the long steep hills we have here in East TN. He said the problem turned out to be the transmission wasn't downshifting properly and was lugging the engine too much. I thought that might be your problem.

 

BTW, check the bottom radiator hose and make sure it is good. I've known old hoses to collapse and be sucked together when the engine is riving high and pulling hard. That will make one overheat. Make sure the reinforcing wire inside the hose isn't missing or damaged.

Edited by Ronnie (see edit history)
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