The Dreaded Porsche 964 Dash Light Christmas Tree Effect
By Air Brigade Member Keith Antal
I had an interesting problem on our last PCA group drive from Hickory, North Carolina. The Hickory PCA area of the Carolina’s region had planned a 4-day trip to New Bern, North Carolina. New Bern is near the coast of the Atlantic Ocean. The trip was planned for the first week of March so we were anticipating good weather and a good time at the Ocean (this was prior to the coronavirus crisis ramping up in North Carolina.
Donna and I drove our black 1992 Porsche 964 in a caravan with three other Porsches. This is the same vehicle that we had driven in Air Brigade, PCA and Blue Ridge Touring Group drives. I rebuilt the engine (myself) at 110,000 miles so I know the car and the mechanics of this Porsche 964 inside and out.
We were all cruising along enjoying the drive when all of a sudden I encountered the dreaded “Christmas Tree Effect” where all the instrument panel emergency lights came on at once. All the emergency lights were on even though the engine ran normal. Then after 20 miles the engine started randomly jerking. We all pulled off at the next exit. This was the first time I was testing my new two-way radios as I was able to communicate that we needed to pull off at the next exit to try and identify the problem.
I called the Porsche of Hickory dealership Sales manager and asked if their sister dealership had a good air-cooled mechanic in Greensboro which was 30 miles away. The Porsche Hickory Sales Manager called Greensboro and they said would watch for me. We made to Greensboro with our friends escorting us to be sure we arrived safely. We thanked our friends and sent them on to New Bern to continue their journey since we were now in good hands.
The Greensboro dealership jumped on the car right away since they knew we were on a PCA drive. While waiting as they worked on it we enjoyed the eye candy in their show room which had Porsche, Ferrari, Maserati and Aston Martin new vehicles. If you are ever near Greensboro you should stop and enjoy the dealership.
The Service Advisor returned from the shop and said the dual distributor Halt sensor was scrambling signals to the computer. They also noted that there could be something else wrong after the distributor problem is fixed. It was Thursday and they would check their sources for a distributor and I said I would check my sources. The dealer came back with good news / bad news. They found a new distributor replacement but it was in Germany and was expensive to ship it to Greensboro. Thus I found a rebuilt one at Pelican Parts in CA with a 2-year warranty and they could overnight it. I ordered it and then decided to rent a vehicle to continue on to New Bern to meet up with the group. Needless to say, National Car Rental didn’t have a Porsche to rent so it was Toyota-time on a Porsche drive.
We had a great time with our friends even though we struggled keeping up with the better performing Porsches. We did catch a lot of heat with our hamster-powered Toyota but we still had fun. Staying in contact with Greensboro Porsche we decided to leave a day early to pick up the Porsche in Greensboro on Saturday.
We found out that they only solved the engine jerking problem with the replacement distributor but they could not promise the emergency lights would not come on unless we left the 964 there for them to find the dreaded electrical gremlins (which could take a lot longer).
I said I wanted to get it home to further trouble shoot the electrical system myself. I thanked them for jumping on the vehicle immediately and having their mechanic come in on Saturday to install the dual distributor. They were so accommodating. I drove it home and even though the Christmas Tree Light effect came back on after 50 miles the engine ran great.
Once back at the ranch I performed a search on the Porsche 964 blog and found this was a common problem in older air-cooled Porsches. They said it was old plug wires, a bad ground or bad coils. I had replaced my wires, plugs and coils when I rebuilt the engine at 110,000 miles and just replaced the wires and plugs last year at 220,000 miles. I had not replaced the coils last year. Thus I ordered new coils and went over to a friend’s man cave garage who has a lift and replaced the coils, ignition modules and battery ground cable.
Bingo, it solved the problem. With 227,000 miles on the odometer, I’m still driving and enjoying my great German-Engineered Porsche 964.
Anyway thought this info may help you Air-Cooled guys if you ever encounter the dreaded “Christmas Tree Lights Effect”.
Edited by Jim Moore
Tags: Porsche 964, Porsche Christmas Tree Light Effect, Porsche electrical gremlin troubleshooting
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