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Discussion Starter · #1 ·
What would cause the heater in a 99 VT Diablo not to work? Everything else with the car seems to work ok.

Thanks
Ken
 

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Does you control panel display light up?, does the ac work?, does it blow cold air?
Mark
 

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Discussion Starter · #3 ·
The control panel lights up and the a/c works. Problem is only cold air blows out when the heater is selected. Also of note, when the A/C is on during the summer the windshield frosts up because the vents on the dash do not close and cold air blows on the windshield. Could the car have a problem where the vents are not closing and the A/C and heater are not being engaged properly?

Ken
 

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Could the car have a problem where the vents are not closing and the A/C and heater are not being engaged properly?
Sounds like you have some broken or disconnected vacum hoses that control the vent flaps and heater valve. I'll look at the schematic Mon. & see if I can determine where you should look for problems first.
 

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FWIW, my [91] diablo used to blow just cold air [as cold as 5 degrees C]. The problem turned out to be the ECU.
 

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.....and it took months for me to track down the problem...I'm no expert, and know much less about this than JRV has fortgotten, but this is where I would start....

1. Check all relevant relays and fuses, for example there is a fuse to the electrovalve that lets hot coolant into the a/c unit.
2. The electrovalve is either on or off, and a slight click can be heard if it is operating. There should be an electrical resistance of about 15 ohm across the electrovalve. [its located above your passengers right shin. With the ignition on and HI selected on the aircon, you should be able to measure some dc voltage intermittently trying to open/close the electrovalve. My manual states that when the electrovalve is DE_ENERGISED, it allows hot water to flow.
3.Check the sensors that tell the electronics what to do. There are four sensors:

Outside air temp [by the horns in front of the passenger wheel], I was able to check mine by taking off front wheel and [difficult access with mirrors] getting in from the wheel-well.

Passenger compartment temp - easiest to check [ by the front passenger right knee] . Should have resistance of 11500ohm at 22 degrees C, 20000ohm at 10 degrees, and 7900ohm at 30 C

Evaporator temp sensor - plugs into right side of evaporator, easy[ish] to get at, but only prevents the system from icing the evaporator, unlikely to be the culprit.

Evaporator outlet sensor, hard to get at, I took out all the pod instruments and used mirrors, should have 12500ohms at 20 degrees, C, has exactly the same electrical properties as the external air sensor [physically different]

I dont think your problem is one of air distribution, vacum lines, as this has nothing to do with the generation of air of the right temperature. I too used to get icing on my screen.

Hope this helps
 

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Discussion Starter · #9 ·
Mike:

Thanks for the great info.

As to the ECU, where is the best place to purchase a new one? Lamborghini of USA wants way too much money for this item. Someone has to have it cheaper. Is it possible to repair the broken one?

Ken
 

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Are you getting hot coolant to the heater unit?, if not check the solenoid.

Mark
 

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suspect the ECU last, much more likely to be a bad sensor, bad contact on a sensor or the electrovalve.

ECU part no for my car is 004526659, priced on Lambostuff at $329
 
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