Intermittent Temp Gauge / A/C Operation

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Ralf_CT
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Intermittent Temp Gauge / A/C Operation

Post by Ralf_CT »

I've just bought a '94 Fox 1600 AT with a strange intermittent electrical problem. When I initially viewed the car the temp gauge and A/C worked, a few days later both stopped working, then a day or so later both came on again only to fail again the next day.

I seem to have an electrical problem which affects both the temp gauge and the A/C simultaneously. Any ideas?

Many thanks for any tips to sort this out.
1994 VW Fox 1.6 (HM) AT 138,225km
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panic-mechanic
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Re: Intermittent Temp Gauge / A/C Operation

Post by panic-mechanic »

Change the water temperature sensor on the front of the head. Sits on the water extension housing.
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Ralf_CT
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Re: Intermittent Temp Gauge / A/C Operation

Post by Ralf_CT »

panic-mechanic wrote:Change the water temperature sensor on the front of the head. Sits on the water extension housing.
Why would a malfunctioning water temp sensor also affect the A/C? It should be easy to check the sensor, short the cable to earth to check if the gauge then works.
1994 VW Fox 1.6 (HM) AT 138,225km
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Re: Intermittent Temp Gauge / A/C Operation

Post by panic-mechanic »

Engine self preservation. If you don't know what the engine temp is it is safer to not add extra load by letting the aircon run.
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Ralf_CT
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Re: Intermittent Temp Gauge / A/C Operation

Post by Ralf_CT »

The previous owner fitted an aftermarket temp gauge above the parcel shelf, this seems to be getting it's feed from a sensor between No. 3 and 4. There's also a sensor on the extension housing, I assume this feeds the factory temp gauge? I'll check it later.
1994 VW Fox 1.6 (HM) AT 138,225km
Ralf_CT
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Re: Intermittent Temp Gauge / A/C Operation

Post by Ralf_CT »

I've got one sensor on top of the extension housing (feeding the aftermarket temp gauge), and one at the bottom of the extension housing feeding the OEM temp gauge. I've got 0.15 V when checking between the feed wire and earth, and around 1,500 ohms when checking across the switch with the engine cold? Also, with the interior fan on '1', if I switch on the A/C it briefly engages and disengages the clutch (possibly not enough voltage to hold the clutch).

Questions:

1. Where does the temp gauge get its feed (all fuses are fine)?
2. What should the voltage be?
3. How are the A/C and temp gauge feeds related?
1994 VW Fox 1.6 (HM) AT 138,225km
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Re: Intermittent Temp Gauge / A/C Operation

Post by panic-mechanic »

Wait single pole sensors? Is this a carb car or management?
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Ralf_CT
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Re: Intermittent Temp Gauge / A/C Operation

Post by Ralf_CT »

panic-mechanic wrote:Wait single pole sensors? Is this a carb car or management?
Simple carb. '94 1600 Fox.
1994 VW Fox 1.6 (HM) AT 138,225km
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Re: Intermittent Temp Gauge / A/C Operation

Post by panic-mechanic »

Nonthen I actually doubt the aircon operation is linked to the temp at all. It's only on cars with management and where hvac talks to the engine module where it considers engine temp.
Your has basic pressure switches and thatbis it. So possibly just low gas in the system.
Stephan van Tonder - Jhb - Putfontein Benoni
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Re: Intermittent Temp Gauge / A/C Operation

Post by Ralf_CT »

panic-mechanic wrote:Nonthen I actually doubt the aircon operation is linked to the temp at all. It's only on cars with management and where hvac talks to the engine module where it considers engine temp.
Your has basic pressure switches and thatbis it. So possibly just low gas in the system.
It must have something to do with the power supply (if only I had a wiring diagram). On the weekend the temp gauge worked... and the A/C (cools beautifully, gas okay). Later the temp gauge stopped working, as did the A/C. What I have noticed is that the A/C clutch briefly engages and immediately disengages when the temp gauge isn't working, but engages fully when the temp gauge works.

Whoever serviced this car the past few years let the owner drive a car where the carb vacuum module increases the idle to +-1,600RPM when the A/C switches on. That not only stresses the gearbox if one then selects 'D'/'R' but it can also cause one to lurch forward when standing at the robots, never mind the mini stall test the torque converter has to endure and the lack of engine braking. I'll have to reset the module push-rod ASAP. My mom has strict instructions NOT to use the A/C.
1994 VW Fox 1.6 (HM) AT 138,225km
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