New owner has a few questions

I took my '99 Roadster out for a 150 mile drive today. I took the top off and stored it on the engine cover. Lunch was 70 miles away and while I ate I left the rear hatch open to cool off the engine. It was 86 today but not too humid. After lunch I put in gas and rode home. Once I slowed down the car just stalled but none of the sensors for the water or oil seemed too high. A little later it did it again. Was it just too hot to slow down or should I look somewhere else? I had the air running the whole time as I couldn't turn it off. Is there a switch for off? The manual didn't address it.

I am still breaking the Kevlar clutch and haven't opened it up yet. I sure like driving with the roof off. The car looks great with it down and people just love it. There are also fans on both sides of the rear of the car. The one on the drivers side ran most of the time even when I was moving. The one on the passenger side seem to go on and off more. I guess one is for the radiator. Are they both for the cooling system or is one for the air conditioning?

I washed the car and now it is in the garage with the battery tender on it and the car is covered. It will be ready for my next trip.

As far as the stalling, I dont have a clue. could be a grounding issue. I have an older Diablo, so a lot of the problems I run into are different. My radiator fan on the driver side runs when the A/C is on like yours. Both radiator fans should come on at a certain temp to cool the engine. Usually in traffic, mine will come on, and on the highway, the fans are shut off. Doesnt sound like you are having over heat issues which mine was suffering from.

I wish i could be more help.

Sounds like nice drive though.

The drivers side has a radiator and a A/C condensor, the passenger side is just a radiator. I believe the fans come on in stages, the drivers side first then the passenger side as needed.

Heat soak?

Heat soak?

 

Is that like sun stroak for cars? What is it?

mine idles low after it heat soaks for a while, but after a minute or two of driving it returns to normal

You guys have A/C that works? Damn

Hi guys. Let me put in my 2 cents worth.

1st issue. My 91 will die once in a while after reving the engine at a regular to slightly high operating temp. Not a big deal, She restarts without trouble. Our cars do not have what is called a "dashpot" . It is a device that keeps the throttle from slamming shut when you blip the throttle. Its kind of like a shock absorber for the throttle bodies. The sudden reduction in air flow can stall the engine. Again not a big deal. A little embarassing at times, but no harm.

2nd issue. The a/c compressor is always running in our cars. That is not exactly a good thing. I would strongly reccomend a small switch installed in the dash that activates a relay to supply power to the a/c clutch. Being able to shut the a/c compressor off in a near overheat situation can be a life saver. Not to mention, the compressor does not need to be on when it is 40 degrees outside. All it is doing is robbing power and freezeing up the evaporator.

3rd issue. Yes the fans come on as needed and independantly. However, I have wired mine to always be on when I turn the key on. It gets 115 degrees in Phoenix. You can never have too much cooling ability here.

Hi guys. Let me put in my 2 cents worth.

1st issue. My 91 will die once in a while after reving the engine at a regular to slightly high operating temp. Not a big deal, She restarts without trouble. Our cars do not have what is called a "dashpot" . It is a device that keeps the throttle from slamming shut when you blip the throttle. Its kind of like a shock absorber for the throttle bodies. The sudden reduction in air flow can stall the engine. Again not a big deal. A little embarassing at times, but no harm.

2nd issue. The a/c compressor is always running in our cars. That is not exactly a good thing. I would strongly reccomend a small switch installed in the dash that activates a relay to supply power to the a/c clutch. Being able to shut the a/c compressor off in a near overheat situation can be a life saver. Not to mention, the compressor does not need to be on when it is 40 degrees outside. All it is doing is robbing power and freezeing up the evaporator.

3rd issue. Yes the fans come on as needed and independantly. However, I have wired mine to always be on when I turn the key on. It gets 115 degrees in Phoenix. You can never have too much cooling ability here.

Good helpful info. I think a cut off on air would be a good addition when the roof is off.

Hi guys. Let me put in my 2 cents worth.

1st issue. My 91 will die once in a while after reving the engine at a regular to slightly high operating temp. Not a big deal, She restarts without trouble. Our cars do not have what is called a "dashpot" . It is a device that keeps the throttle from slamming shut when you blip the throttle. Its kind of like a shock absorber for the throttle bodies. The sudden reduction in air flow can stall the engine. Again not a big deal. A little embarassing at times, but no harm.

2nd issue. The a/c compressor is always running in our cars. That is not exactly a good thing. I would strongly reccomend a small switch installed in the dash that activates a relay to supply power to the a/c clutch. Being able to shut the a/c compressor off in a near overheat situation can be a life saver. Not to mention, the compressor does not need to be on when it is 40 degrees outside. All it is doing is robbing power and freezeing up the evaporator.

3rd issue. Yes the fans come on as needed and independantly. However, I have wired mine to always be on when I turn the key on. It gets 115 degrees in Phoenix. You can never have too much cooling ability here.

 

Can you elaborate on the switch to cut off the power to the A/C? A detailed explanation on how to do this would be great.

Can you elaborate on the switch to cut off the power to the A/C? A detailed explanation on how to do this would be great.

 

+1

 

Allan also mentioned this. Gary, maybe I could drop by this week and we could do this.

I'm not exactaly sure what your stalling is due to, but I had a similar problem with my 98 SV. Car can great, but when I would back off the throttle and put in the clutch as when coming to a stop the RPMs would fall to nothing and the car would stall. Blipping the throttle after I put the clutch in as the RPMs were falling would catch the fall and no problem. I got really good at heal-toe in a car not set up real well for that!! Took the car in and the guys adjusted the idle and the car has been fine ever since. My car was idling smothly at about 800-900 RPM which apparently too low. Adjusting it to about 1000-1100 solved the problem. Seems the car always undershoots the idle target a little, so I think the "dashpot" issue brought up is likely legit. Certainly, other problems could be at fault such as ground, vacuum, etc. Get it checked out. I doubt it will be a big deal.

 

As for the fans, the drivers side fan always comes on above 70 degrees ambient temp when at idle or slow driving. The right side fan comes on when needed for additional cooling. The AC stays on all the time just as in modern cars as the climate control goes to a set temp. Even when cold, the system sometimes needs it to keep moisture out to prevent window fogging, etc.

 

Hope this helps. Glad to see your are enjoying your car - and for god sakes get that cluthc broke in so you can really run it!!.

 

Steve

The 99MY has a "carter motor" or what I call an idle spped control. Its located in thecenter of the intake towards the front. (under the cover) Check to see if its working. Someones web site had a nice descrip of this

The a/c compressor is always running in our cars.

The compressor should not always run. The A/C system is thermostat controlled. The A/C system cannot be turned completely off unless you install "the switch".

The drivers side has a radiator and a A/C condensor, the passenger side is just a radiator. I believe the fans come on in stages, the drivers side first then the passenger side as needed.

The drivers side is turned on when the A/C compressor is engaged. Additionally, both are controlled by radiator temp.

I had the air running the whole time as I couldn't turn it off.

You cannot shutoff the low fan speed. To stop the A/C engaging, just up the thermostat temp setting. You will distinctly hear the A/C compressor disengage and the driver side fan stop.

It was 86 today but not too humid. After lunch I put in gas and rode home. Once I slowed down the car just stalled but none of the sensors for the water or oil seemed too high. A little later it did it again. Was it just too hot to slow down or should I look somewhere else?

I've driven my car in 117 degree heat and as long as the various temp sensors are ok, I've never had a problem like you describe.

 

-mick ('99 roadster)

Always happy to help.

There is only 1 12volt power wire that creates the magnetic field to engauge the compressor clutch. It will need to be cut and a 30 amp relay will be the gateway to supply power. The toggle switch goes to ground when turned on. Just mount the toggle switch in a good place in the dash.

The compressor should not always run. The A/C system is thermostat controlled. The A/C system cannot be turned completely off unless you install "the swtich"

The compressor is always engauged as soon as the car is started regardless of the a/c thermostat position on the older Diablos. The biggest advantage to "the switch" is to allow the car's engine cooling system to work more efficiently in the event of a near overheat situation. Most older Diablos have this problem in hotter climates.

The compressor is always engauged as soon as the car is started regardless of the a/c thermostat position on the older Diablos.

Not so on a 99 at least. The compressor is fitted with a normal clutch and that is tied to the driver side fan and the interior thermostat.

 

-mick

Not so on a 99 at least. The compressor is fitted with a normal clutch and that is tied to the driver side fan and the interior thermostat

The a/c clutch is still normal on the older cars, but you see thats where the "catch 22" comes into play. As soon as the car gets hot enough to turn on the drivers side fan (whether you are running the a/c or not), the a/c clutch will automatically engauge. The condenser will generate heat and then compromise the engines cooling ability.

There's the method to my madness.

The a/c clutch is still normal on the older cars, but you see thats where the "catch 22" comes into play. As soon as the car gets hot enough to turn on the drivers side fan (whether you are running the a/c or not), the a/c clutch will automatically engauge. The condenser will generate heat and then compromise the engines cooling ability.

There's the method to my madness.

And on the 99 (at least) all you do it up the thermostat to kill the A/C. If the drivers side fan runs based on engine temp, the A/C is not re-engaged. The driver side fan is controlled by a relay output with multiple distinct "inputs" ie there is no electrical path back to the A/C compressor from the fan.

 

I have the schematics but it will be next weekend before I can figure out exactly why all this is so.

 

-mick

I took a look at my manual. It appears relay 19 has the dual output that feeds the left fan AND the clutch (wire f33) on the older cars.

There must have been a change on the 2nd generation Diablos.

I took a look at my manual. It appears relay 19 has the dual output that feeds the left fan AND the clutch (wire f33) on the older cars.

Ok... so we agree that the compressor should not always run unless called for? Or do you know what is the input to your relay 19?

 

-mick

No, I'm not trying to be a weenie.

But on the 1st generation cars, as soon as R19 turns on for the left fan, F33 splits in 2 and will inadvertently engauge the a/c clutch.

But on the 1st generation cars, as soon as R19 turns on for the left fan, F33 splits in 2 and will inadvertently engauge the a/c clutch.

Ok - this is consistant to what I see on a 99. A/C compressor runs, driver fan runs. However, there are multiple paths to the fan.

 

What would be interesting to know is what is the input to your r19? Is it "hard wired" or somehow run back to the thermostat?

 

-mick

I am having a hard time chasing it. I can't tell if term 85 or 86 on R19 is the activator. I give up. I think I need reading glasses.

My hat is off to you for a great debate.

I am having a hard time chasing it. I can't tell if term 85 or 86 on R19 is the activator. I give up. I think I need reading glasses. My hat is off to you for a great debate.

Cheers to you too. I'm bummed that my schematics are 120 miles away......

 

-mick