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ThomasJoseph315 · Guest

Ok A-team,..

Symptoms: highway sometimes 3/4, most times at halfway. Low speeds does the same thing but more often

Headlights instantly make the reading higher buy 1/4

Where is the normal setting for the temp gauge?

new thermo recently installed, haven't ruled out re bleeding the system, how is this done?

How do I test the fans? Is there two speeds? How should the operate? On all the time, or no?

Whatcha got?

924RACR · Posted: Mon Feb 17, 2014 7:57 am Post subject:

Sounds like you need to fix the ground for the gauge.

Wouldn't hurt to check the power supply to it also...
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Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
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brian19600 · Joined: 28 Oct 2013 Posts: 375 Location: NJ/CT

Headlights affecting temperature gauge can mean an issue with your grounds. Have you cleaned your under dash grounds?

There are 2 speeds. The lower speed only comes on when the ignition is off and the radiator still requires cooling.
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78 924

maybeoneday · Posted: Mon Feb 17, 2014 8:27 am Post subject:

As far as the actual overheating or even if your car is or is not overheating I don't want to say too much. It is quite possible, maybe even probable, that you have a problem with the cooling system in addition to the possible problem I will suggest. However, it is going to be a little hard to trust your temp gauge until you get it reading correctly.

The fact that the headlights make the gauge rise by about a 1/4 sounds like a bad ground connection somewhere. It sounds like the temp gauge is drawing current from another circuit (I am guessing that neither the heat produced by the lights or the change in air flow is enough to cause a temp rise of this magnitude). Because the lights draw a large amount of current from the chassis when turned on, if there is a bad ground connection, the path of high resistance created by the lights could cause the the gauge (or its sender) to change because of a changed reference point. I would start by having a look at the ground connections under the dash and progress from there. Sounds like you are going to have some multimeter fun, this sort of problem can take a while to find and fix. Hope this helps.

Hope this helps
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1977 924 NA Auto

maybeoneday · Posted: Mon Feb 17, 2014 8:29 am Post subject:

wow, three replies all with a similar theory all at once. There was not 1 reply up when I started typing, that is impressive.
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1977 924 NA Auto

larchie · Joined: 19 Jun 2003 Posts: 297

ThomasJoseph315 · Guest

Yea,.. I need to check for grounding. i guess. anyone have a diagram or a pic to where the ground is? I know there is a star cluster under the dash, but is their only one? Any ussual suspects? I was thinking of running a 12 gauge wire from the ground near the battery box and running it to that cluster.

Is there something wrong with the body's of these cars that they won't hold aground after a while? Is this just where the wire touches the local ground? I know anything is possible, but if all I have to do is wiggle some wires I'll be happy, but if it's something where i got to wire a ground to every spot in the car? good grief, lol.

How about the ussual spots and I'll go from there... oh one other thing that maybe related. the wipers don't work on the regular switch. The swithc works, but maaaaybe all these grounds are screwing up in a central location.

Thanks for the help

ThomasJoseph315 · Guest

Here is your reward for helping me, saw this at a car show today!

larchie · Joined: 19 Jun 2003 Posts: 297

ThomasJoseph315 · Guest

^ thanks for the tips! I'll take a look at those areas. If I have to, I'll simply just run ground wires to these locations if there are only a few of them, that's not that big of a deal for me.

I thought they didn't use Galvanized steel in the early 924's? I got a 76, would that matter?

I got a Hayes manual and know it shows diagrams, but specifically where these points are they don't do a good job pointing this out.

larchie · Joined: 19 Jun 2003 Posts: 297

SilverGhost · Posted: Tue Feb 18, 2014 10:11 am Post subject:

I had the same problem with the headlights affecting the temperature gauge.

After chasing about for a while with a multimeter I determined that the connection between the strap from the body to the engine was poor, and that the problem lay in the fact that the inlet manifold bolt at the engine end of that strap was poorly connected to the engine block.

Fitting an additional heavy earth strap between a bell housing bolt and a coil mounting bolt fixed the temperature gauge problem, and also made the fuel gauge reading much steadier.
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"Priscilla" 1981 924 NA RoW auto, metallic blue

ThomasJoseph315 · Guest

I've replaced the short ground cable in battery bay from the batt to the body with a 4 gauge wire because it was crumbling. I also ran a 4 gauge wire from the batt ground to the engine for the starter. There is also a new 8 gauge wire from the batt ground to the alt. There is a factory 4 gauge wire from the coil to another intake bolt, I'll replace that one tomorrow.

Grrrrrrrrrounds :/

SilverGhost · Posted: Tue Feb 18, 2014 5:45 pm Post subject:

Don't stress ThomasJoseph315. Keep the faith and keep at it.
Once you've sorted the half dozen or so common issues with old 924s, you'll have a great looking, fun, reliable car.
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"Priscilla" 1981 924 NA RoW auto, metallic blue

ThomasJoseph315 · Guest

long day,,...

turns out it was the headlight switch. I had to clean it.

Tired,.. I'll post more tomorrow.